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Source: https://theconversation.com/us/topics/astronomy-50/articles.atom

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  3.  <id>tag:theconversation.com,2011:/us/topics/astronomy-50/articles</id>
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  6.  <title>Astronomy – The Conversation</title>
  7.  <updated>2024-12-31T21:47:21Z</updated>
  8.  <entry>
  9.    <id>tag:theconversation.com,2011:article/242601</id>
  10.    <published>2024-12-31T21:47:21Z</published>
  11.    <updated>2024-12-31T21:47:21Z</updated>
  12.    <link rel="alternate" type="text/html" href="https://theconversation.com/a-total-eclipse-of-the-moon-saturns-rings-disappear-meteors-and-more-your-guide-to-the-southern-sky-in-2025-242601"/>
  13.    <title>A total eclipse of the Moon, Saturn’s rings ‘disappear’, meteors and more: your guide to the southern sky in 2025</title>
  14.    <content type="html">&lt;figure&gt;&lt;img src="https://images.theconversation.com/files/629166/original/file-20241031-15-36hs3q.jpg?ixlib=rb-4.1.0&amp;amp;rect=49%2C24%2C5472%2C3612&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=496&amp;amp;fit=clip" /&gt;&lt;figcaption&gt;&lt;span class="caption"&gt;The totally eclipsed Moon on 26 May 2021.&lt;/span&gt; &lt;span class="attribution"&gt;&lt;span class="source"&gt;Geoffrey Wyatt, Powerhouse Museum&lt;/span&gt;, &lt;a class="license" href="http://creativecommons.org/licenses/by/4.0/"&gt;CC BY&lt;/a&gt;&lt;/span&gt;&lt;/figcaption&gt;&lt;/figure&gt;&lt;p&gt;In addition to the annual parade of star pictures or constellations passing above our heads each night, there are always exciting events to look out for in the sky. The year 2025 is no exception and has its fair share of such events.&lt;/p&gt;
  15.  
  16. &lt;p&gt;Though the night sky is more spectacular from a dark country sky, you can see the events outlined here even if, like many others, you live in a light-polluted city. For most events you do not need a telescope or binoculars.&lt;/p&gt;
  17.  
  18. &lt;p&gt;Here are some of the highlights.&lt;/p&gt;
  19.  
  20. &lt;h2&gt;March and September: eclipses of the Moon&lt;/h2&gt;
  21.  
  22. &lt;p&gt;During the early morning of Monday 8 September, the full Moon will move into the shadow of Earth and be totally eclipsed. The Moon will turn a red or coppery colour, because sunlight is bent or refracted by Earth’s atmosphere onto the Moon. The bent light is red, as we are looking at the reflection of sunrises and sunsets from around the globe.&lt;/p&gt;
  23.  
  24. &lt;p&gt;Total eclipses of the Moon are more common than those of the Sun. They can be seen from all the regions on Earth where it is night. &lt;/p&gt;
  25.  
  26. &lt;p&gt;Unlike eclipses of the Sun, lunar eclipses are safe to watch with the unaided eye. They are also safe to photograph. A tripod will help, as will a camera or phone able to take timed exposures.&lt;/p&gt;
  27.  
  28. &lt;p&gt;The eclipse starts with Earth’s shadow gradually covering the Moon over about an hour. Similarly, after totality the shadow takes about an hour to leave the Moon. &lt;/p&gt;
  29.  
  30. &lt;p&gt;Seen from Australia’s east coast, the total eclipse will last from from 3:30am to 4:53am on September 8. From New Zealand, this will be from 5:30am to moonset; from South Australia or the Northern Territory, 3:00am to 4:23am, and from Western Australia 1:30am to 2:53am.&lt;/p&gt;
  31.  
  32. &lt;p&gt;Earlier in the year, on the evening of Friday March 14, people in Aotearoa New Zealand will be able to see a totally eclipsed Moon as it rises above the horizon just after sunset. Watchers in eastern Australia will also get a brief glimpse of a partially eclipsed Moon after moonrise, for 34 minutes from Sydney, 43 minutes from Brisbane and 16 minutes from Cairns.&lt;/p&gt;
  33.  
  34. &lt;h2&gt;March: Saturn’s ‘disappearing’ rings&lt;/h2&gt;
  35.  
  36. &lt;p&gt;Gazing at Saturn and its rings through a telescope is always a thrill, whether you are seeing them for the first or the hundredth time. However, in early 2025 the &lt;a href="https://theconversation.com/will-saturns-rings-really-disappear-by-2025-an-astronomer-explains-217370#:%7E:text=That's%20what's%20happening%20in%202025,once%20again%20in%20March%202025."&gt;rings will seem to vanish&lt;/a&gt; as Earth passes through the plane of the rings.&lt;/p&gt;
  37.  
  38. &lt;p&gt;This phenomenon occurs twice during Saturn’s 29-year path around the Sun, that is, at roughly 15-year intervals. Unfortunately, on March 24, the date when this will occur, the planet will be too close to the Sun in the sky for us to observe.&lt;/p&gt;
  39.  
  40.  
  41.  
  42. &lt;p&gt;However, in the evenings until mid-February and in the morning from late March we will be able to see Saturn with quite narrow, tilted rings.&lt;/p&gt;
  43.  
  44. &lt;p&gt;Note that a small telescope is needed to see Saturn with or without its rings. If you don’t have one yourself, you can go on a night tour at a public observatory like &lt;a href="https://powerhouse.com.au/program/sydney-observatory-tours?details=open"&gt;Sydney Observatory&lt;/a&gt; or an observing session with a local astronomical group, such as those at Melbourne Observatory with the &lt;a href="https://asv.org.au/Stellar-Nights-At-Melbourne-Observatory/"&gt;Astronomical Society of Victoria&lt;/a&gt;.&lt;/p&gt;
  45.  
  46. &lt;h2&gt;May and December: meteor showers&lt;/h2&gt;
  47.  
  48. &lt;figure class="align-right zoomable"&gt;
  49.            &lt;a href="https://images.theconversation.com/files/635792/original/file-20241203-15-iqghsj.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=1000&amp;amp;fit=clip"&gt;&lt;img alt="Photo of streaks of light coming from a dark, starry sky." src="https://images.theconversation.com/files/635792/original/file-20241203-15-iqghsj.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=237&amp;amp;fit=clip" srcset="https://images.theconversation.com/files/635792/original/file-20241203-15-iqghsj.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=903&amp;amp;fit=crop&amp;amp;dpr=1 600w, https://images.theconversation.com/files/635792/original/file-20241203-15-iqghsj.jpg?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=903&amp;amp;fit=crop&amp;amp;dpr=2 1200w, https://images.theconversation.com/files/635792/original/file-20241203-15-iqghsj.jpg?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=903&amp;amp;fit=crop&amp;amp;dpr=3 1800w, https://images.theconversation.com/files/635792/original/file-20241203-15-iqghsj.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=1135&amp;amp;fit=crop&amp;amp;dpr=1 754w, https://images.theconversation.com/files/635792/original/file-20241203-15-iqghsj.jpg?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=1135&amp;amp;fit=crop&amp;amp;dpr=2 1508w, https://images.theconversation.com/files/635792/original/file-20241203-15-iqghsj.jpg?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=1135&amp;amp;fit=crop&amp;amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"&gt;&lt;/a&gt;
  50.            &lt;figcaption&gt;
  51.              &lt;span class="caption"&gt;The Eta Aquariids seen from Chile in 2022.&lt;/span&gt;
  52.              &lt;span class="attribution"&gt;&lt;a class="source" href="https://www.eso.org/public/images/potw2227b/"&gt;Petr Horálek / ESO&lt;/a&gt;, &lt;a class="license" href="http://creativecommons.org/licenses/by/4.0/"&gt;CC BY&lt;/a&gt;&lt;/span&gt;
  53.            &lt;/figcaption&gt;
  54.          &lt;/figure&gt;
  55.  
  56. &lt;p&gt;The two main meteor showers of the year are the Eta Aquariids and the Geminids. &lt;/p&gt;
  57.  
  58. &lt;p&gt;In 2025, the Eta Aquariids are best seen on the morning of Wednesday May 7, while the Geminids will be most visible on the mornings of Sunday December 14 and Monday December 15. &lt;/p&gt;
  59.  
  60. &lt;p&gt;This year, viewing conditions for both meteor showers are favourable, in the sense that there will be no bright Moon in the sky during those mornings. To see them, look towards the north-east (Eta Aquariids) and north (Geminids) before dawn starts brightening the sky. &lt;/p&gt;
  61.  
  62. &lt;p&gt;The darker the sky you can find, the better. Keep away from street lights or any other light.&lt;/p&gt;
  63.  
  64. &lt;h2&gt;January, April and August: planets&lt;/h2&gt;
  65.  
  66. &lt;p&gt;The five planets you can see with the naked eye – Mercury, Venus, Mars, Jupiter and Saturn – move across the sky along a line called the &lt;a href="https://earthsky.org/space/what-is-the-ecliptic/"&gt;ecliptic&lt;/a&gt;.&lt;/p&gt;
  67.  
  68. &lt;p&gt;As the planets move, they sometimes appear to pass close to each other and take on interesting patterns. Of course, they only appear close from our point of view. In reality the planets are tens or hundreds of million kilometres apart. &lt;/p&gt;
  69.  
  70. &lt;p&gt;In 2025, these patterns include:&lt;/p&gt;
  71.  
  72. &lt;ul&gt;
  73. &lt;li&gt;&lt;p&gt;January 18–19: the brightest planet, Venus, is close to the ringed planet Saturn in the evening sky&lt;/p&gt;&lt;/li&gt;
  74. &lt;li&gt;&lt;p&gt;April 1–15: Mercury, Venus and Saturn form a slowly changing compact group in the eastern sky near sunrise&lt;/p&gt;&lt;/li&gt;
  75. &lt;li&gt;&lt;p&gt;August 12–13: Venus and Jupiter, the two brightest planets, are only separated by two moon-widths in the morning sky.&lt;/p&gt;&lt;/li&gt;
  76. &lt;/ul&gt;
  77.  
  78. &lt;h2&gt;June and August: constellations&lt;/h2&gt;
  79.  
  80. &lt;p&gt;As the year progresses, different constellations appear in the evening sky. The perpetual chase of Orion and Scorpius (the hunter and the scorpion) across the sky was &lt;a href="https://theconversation.com/meteors-supermoons-a-comet-and-more-your-guide-to-the-southern-sky-in-2024-217927"&gt;noted in 2024&lt;/a&gt;.&lt;/p&gt;
  81.  
  82. &lt;p&gt;In 2025, keep an eye on the Southern Cross (known as Crux to astronomers) and Sagittarius (the archer).&lt;/p&gt;
  83.  
  84.  
  85.  
  86. &lt;p&gt;The Southern Cross is the best-known constellation in the southern sky. It is easy to find, as it is made up of a compact group of bright stars in the shape of a cross. &lt;/p&gt;
  87.  
  88. &lt;p&gt;Two pointer stars from the neighbouring constellation of Centaurus, the centaur, also help to show its position. From Sydney and further south, the Southern Cross is always above the horizon. However, in the evenings, it is best viewed around June, when it is high in the southern sky.&lt;/p&gt;
  89.  
  90.  
  91.  
  92. &lt;p&gt;The constellation Sagittarius is next to Scorpius. In the evenings, it is best placed for observation in August, as at that time of the year it is directly overhead. &lt;/p&gt;
  93.  
  94. &lt;p&gt;A join-the-dots look at the brightest stars of the constellation gives the impression of a teapot, and it is often referred to by that name. Sagittarius is an important constellation for Australian astronomers, as it contains the &lt;a href="https://www.eso.org/public/images/eso0846a/"&gt;centre of the Milky Way galaxy&lt;/a&gt;.&lt;/p&gt;
  95.  
  96. &lt;hr&gt;
  97.  
  98. &lt;p&gt;&lt;em&gt;The information in this article comes from the &lt;a href="https://unsw.press/books/2025-australasian-sky-guide/"&gt;2025 Australasian Sky Guide&lt;/a&gt;. The guide has monthly star maps and has much more information to help with viewing and enjoying the night sky from Australia and Aotearoa New Zealand.&lt;/em&gt;&lt;/p&gt;&lt;img src="https://counter.theconversation.com/content/242601/count.gif" alt="The Conversation" width="1" height="1" /&gt;
  99. &lt;p class="fine-print"&gt;&lt;em&gt;&lt;span&gt;Nick Lomb has received author&amp;#39;s fees for the 2025 Australasian Sky Guide.&lt;/span&gt;&lt;/em&gt;&lt;/p&gt;</content>
  100.    <summary>In 2025 we will see Saturn’s rings ‘disappear’, the Moon turning red, meteor showers and more.</summary>
  101.    <author>
  102.      <name>Nick Lomb, Honorary Professor, Centre for Astrophysics, University of Southern Queensland</name>
  103.      <foaf:homepage rdf:resource="https://theconversation.com/profiles/nick-lomb-1395802"/>
  104.    </author>
  105.    <rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
  106.  </entry>
  107.  <entry>
  108.    <id>tag:theconversation.com,2011:article/243645</id>
  109.    <published>2024-12-26T13:46:47Z</published>
  110.    <updated>2024-12-26T13:46:47Z</updated>
  111.    <link rel="alternate" type="text/html" href="https://theconversation.com/from-new-commercial-moon-landers-to-asteroid-investigations-expect-a-slate-of-exciting-space-missions-in-2025-243645"/>
  112.    <title>From new commercial Moon landers to asteroid investigations, expect a slate of exciting space missions in 2025</title>
  113.    <content type="html">&lt;figure&gt;&lt;img src="https://images.theconversation.com/files/636685/original/file-20241205-15-zofr5y.jpg?ixlib=rb-4.1.0&amp;amp;rect=41%2C52%2C6920%2C4582&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=496&amp;amp;fit=clip" /&gt;&lt;figcaption&gt;&lt;span class="caption"&gt;A host of space missions are planned to launch in 2025. &lt;/span&gt; &lt;span class="attribution"&gt;&lt;a class="source" href="https://newsroom.ap.org/detail/AsteroidMission/0a0d4e5452844e7ea11df1fe90761e2c/photo?Query=asteroid&amp;amp;mediaType=photo&amp;amp;sortBy=&amp;amp;dateRange=Anytime&amp;amp;totalCount=1993&amp;amp;currentItemNo=0"&gt;AP Photo/John Raoux&lt;/a&gt;&lt;/span&gt;&lt;/figcaption&gt;&lt;/figure&gt;&lt;p&gt;In 2024, space exploration dazzled the world. &lt;/p&gt;
  114.  
  115. &lt;p&gt;NASA’s &lt;a href="https://science.nasa.gov/mission/europa-clipper/"&gt;Europa Clipper&lt;/a&gt; began its journey to study Jupiter’s moon Europa. SpaceX’s &lt;a href="https://www.spacex.com/vehicles/starship/"&gt;Starship&lt;/a&gt; achieved its first successful landing, a critical milestone for future deep space missions. China made headlines with the &lt;a href="https://www.cnsa.gov.cn/english/n6465652/n6465653/c10573102/content.html"&gt;Chang’e 6 mission&lt;/a&gt;, which successfully returned samples from the far side of the Moon. Meanwhile, the &lt;a href="https://www.nasa.gov/international-space-station/"&gt;International Space Station&lt;/a&gt; continued to host international crews, including private missions like &lt;a href="https://www.axiomspace.com/missions/ax3"&gt;Axiom Mission 3&lt;/a&gt;.&lt;/p&gt;
  116.  
  117. &lt;p&gt;As an &lt;a href="https://www.careerexplorer.com/careers/aerospace-engineer/"&gt;aerospace engineer&lt;/a&gt;, &lt;a href="https://mabe.utk.edu/people/zhenbo-wang/"&gt;I’m excited&lt;/a&gt; for 2025, when space agencies worldwide are gearing up for even more ambitious goals. Here’s a look at the most exciting missions planned for the coming year, which will expand humanity’s horizons even further, from the Moon and Mars to asteroids and beyond:&lt;/p&gt;
  118.  
  119. &lt;h2&gt;Scouting the lunar surface with CLPS&lt;/h2&gt;
  120.  
  121. &lt;p&gt;NASA’s &lt;a href="https://www.nasa.gov/commercial-lunar-payload-services/"&gt;Commercial Lunar Payload Services&lt;/a&gt;, or CLPS, initiative aims to deliver science and technology payloads to the Moon using commercial landers. CLPS is what brought &lt;a href="https://www.intuitivemachines.com/im-1"&gt;Intuitive Machines’ Odysseus lander&lt;/a&gt; to the Moon in February 2024, marking the first U.S. Moon landing since Apollo.&lt;/p&gt;
  122.  
  123. &lt;p&gt;In 2025, NASA has several CLPS missions planned, including deliveries by companies &lt;a href="https://www.astrobotic.com/"&gt;Astrobotic&lt;/a&gt;, &lt;a href="https://www.intuitivemachines.com/"&gt;Intuitive Machines&lt;/a&gt; and &lt;a href="https://fireflyspace.com/"&gt;Firefly Aerospace&lt;/a&gt;. &lt;/p&gt;
  124.  
  125. &lt;p&gt;These missions will carry a variety of scientific instruments and technology demonstrations to different lunar locations. The payloads will include experiments to study lunar geology, test new technologies for future human missions and gather data on the Moon’s environment.&lt;/p&gt;
  126.  
  127.  
  128.  
  129. &lt;h2&gt;Surveying the sky with SPHEREx&lt;/h2&gt;
  130.  
  131. &lt;p&gt;In February 2025, NASA plans to launch the Spectro-Photometer for the History of the Universe, Epoch of Reionization and Ices Explorer, or &lt;a href="https://www.jpl.nasa.gov/missions/spherex/"&gt;SPHEREx&lt;/a&gt;, observatory. This mission will survey the sky in &lt;a href="https://stonelock.com/what-is-near-infrared-light/"&gt;near-infrared light&lt;/a&gt;, which is a type of light that is invisible to the naked eye but that special instruments can detect. Near-infrared light is useful for observing objects that are too cool or too distant to be seen in &lt;a href="https://science.nasa.gov/ems/09_visiblelight/"&gt;visible light&lt;/a&gt;.&lt;/p&gt;
  132.  
  133. &lt;p&gt;SPHEREx will create a comprehensive map of the universe by surveying and collecting data on more than 450 million galaxies along with over 100 million stars in the &lt;a href="https://science.nasa.gov/resource/the-milky-way-galaxy/"&gt;Milky Way&lt;/a&gt;. Astronomers will use this data to answer big questions about the origins of galaxies and the distribution of water and organic molecules in &lt;a href="https://www.nasa.gov/image-article/stellar-nursery-2/"&gt;stellar nurseries&lt;/a&gt; – where stars are born from gas and dust.&lt;/p&gt;
  134.  
  135.  
  136.  
  137. &lt;h2&gt;Studying low Earth orbit with Space Rider&lt;/h2&gt;
  138.  
  139. &lt;p&gt;The European Space Agency, or ESA, plans to conduct an orbital test flight of its &lt;a href="https://www.esa.int/Enabling_Support/Space_Transportation/Space_Rider"&gt;Space Rider&lt;/a&gt; uncrewed spaceplane in the third quarter of 2025. Space Rider is a reusable spacecraft designed to carry out various scientific experiments in &lt;a href="https://www.space.com/low-earth-orbit"&gt;low Earth orbit&lt;/a&gt;.&lt;/p&gt;
  140.  
  141. &lt;p&gt;These scientific experiments will include &lt;a href="https://www.nasa.gov/learning-resources/for-kids-and-students/what-is-microgravity-grades-5-8/"&gt;research in microgravity&lt;/a&gt;, which is the near-weightless environment of space. Scientists will study how plants grow, how materials behave and how biological processes occur without the influence of gravity.&lt;/p&gt;
  142.  
  143. &lt;p&gt;Space Rider will also demonstrate new technologies for future missions. For example, it will test advanced &lt;a href="https://www.esa.int/Applications/Connectivity_and_Secure_Communications/Telecommunications_satellites"&gt;telecommunication systems&lt;/a&gt;, which are crucial for maintaining communication with spacecraft over long distances. It will also test new &lt;a href="https://www.esa.int/Science_Exploration/Human_and_Robotic_Exploration"&gt;robotic exploration tools&lt;/a&gt; for use on future missions to the Moon or Mars.&lt;/p&gt;
  144.  
  145.  
  146.  
  147. &lt;h2&gt;Exploring the Moon with M2/Resilience&lt;/h2&gt;
  148.  
  149. &lt;p&gt;Japan’s &lt;a href="https://ispace-inc.com/news-en/?p=6120"&gt;M2/Resilience mission&lt;/a&gt;, scheduled for January 2025, will launch a lander and micro-rover to the lunar surface. &lt;/p&gt;
  150.  
  151. &lt;p&gt;This &lt;a href="https://jatan.space/moon-monday-issue-154/"&gt;mission will study&lt;/a&gt; the lunar soil to understand its composition and properties. Researchers will also conduct a water-splitting test to produce oxygen and hydrogen by extracting water from the lunar surface, heating the water and splitting the captured steam. The generated water, oxygen and hydrogen can be used for enabling long-term lunar exploration.&lt;/p&gt;
  152.  
  153. &lt;p&gt;This mission will also demonstrate new technologies, such as advanced navigation systems for precise landings and systems to operate the rover autonomously. These technologies are essential for future lunar exploration and could be used in missions to Mars and beyond.&lt;/p&gt;
  154.  
  155. &lt;p&gt;The M2/Resilience mission is part of Japan’s broader efforts to &lt;a href="https://theconversation.com/japan-is-now-the-5th-country-to-land-on-the-moon-the-technology-used-will-lend-itself-to-future-lunar-missions-221570"&gt;contribute to international lunar exploration&lt;/a&gt;. It builds on the success of Japan’s &lt;a href="https://global.jaxa.jp/projects/sas/slim/"&gt;Smart Lander for Investigating Moon&lt;/a&gt;, or SLIM, mission, which landed on the Moon using a precise landing technique in March 2024.&lt;/p&gt;
  156.  
  157.  
  158.  
  159. &lt;h2&gt;Investigating an asteroid with Tianwen-2&lt;/h2&gt;
  160.  
  161. &lt;p&gt;China’s &lt;a href="https://www.planetary.org/articles/tianwen-2-chinas-near-earth-asteroid-and-comet-double-header"&gt;Tianwen-2&lt;/a&gt; mission is an ambitious asteroid sample return and comet probe mission. Scheduled for launch in May 2025, Tianwen-2 aims to collect samples from a near-Earth asteroid and study a comet. This mission will advance scientists’ understanding of the &lt;a href="https://arxiv.org/html/2404.14982v1"&gt;solar system’s formation and evolution&lt;/a&gt;, building on the success of China’s previous lunar and Mars missions.&lt;/p&gt;
  162.  
  163. &lt;p&gt;The mission’s first target is the near-Earth &lt;a href="https://www.nature.com/articles/s43247-021-00303-7"&gt;asteroid 469219 Kamoʻoalewa&lt;/a&gt;. This asteroid is a quasi-satellite of Earth, meaning it orbits the Sun but stays close to Earth. Kamoʻoalewa is roughly 131-328 feet (40-100 meters) in diameter and may be a fragment of the Moon, &lt;a href="https://spacenews.com/china-to-launch-near-earth-asteroid-sample-return-mission-in-2025/"&gt;ejected into space by a past impact event&lt;/a&gt;. &lt;/p&gt;
  164.  
  165. &lt;p&gt;By studying this asteroid, scientists hope to learn about the early solar system and the processes that shaped it. The spacecraft will use both &lt;a href="https://www.nasa.gov/solar-system/osiris-rex-tags-surface-of-asteroid-bennu/"&gt;touch-and-go&lt;/a&gt; and &lt;a href="https://www.planetary.org/articles/tianwen-2-chinas-near-earth-asteroid-and-comet-double-header"&gt;anchor-and-attach&lt;/a&gt; techniques to collect samples from the asteroid’s surface.&lt;/p&gt;
  166.  
  167. &lt;p&gt;After collecting samples from Kamoʻoalewa, Tianwen-2 will return them to Earth and then set course for its second target, the main-belt &lt;a href="https://www.spacereference.org/comet/311p-panstarrs"&gt;comet 311P/PANSTARRS&lt;/a&gt;. This comet is located in the &lt;a href="https://coolcosmos.ipac.caltech.edu/ask/185-what-is-the-asteroid-belt-"&gt;asteroid belt&lt;/a&gt; between Mars and Jupiter. &lt;/p&gt;
  168.  
  169. &lt;p&gt;By analyzing the comet’s materials, researchers hope to learn more about the conditions that existed in the &lt;a href="https://ucmp.berkeley.edu/education/events/cowen1d.html"&gt;early solar system&lt;/a&gt; and possibly the origins of water and organic molecules on Earth.&lt;/p&gt;
  170.  
  171. &lt;h2&gt;Solar system flybys&lt;/h2&gt;
  172.  
  173. &lt;p&gt;Besides the above planned launch missions, several space agencies plan to perform exciting deep-space flyby missions in 2025.&lt;/p&gt;
  174.  
  175. &lt;p&gt;&lt;a href="https://science.nasa.gov/learn/basics-of-space-flight/primer/"&gt;A flyby&lt;/a&gt;, or gravity assist, is when a spacecraft passes close enough to a planet or moon to use its gravity for a speed boost. As the spacecraft approaches, it gets pulled in by the planet’s gravity, which helps it accelerate. &lt;/p&gt;
  176.  
  177. &lt;p&gt;After swinging around the planet, the spacecraft is flung back out into space, allowing it to change direction and continue on its intended path using &lt;a href="https://newspaceeconomy.ca/2024/03/15/what-is-gravity-assist-and-why-is-it-important/"&gt;less fuel&lt;/a&gt;.&lt;/p&gt;
  178.  
  179. &lt;figure&gt;
  180.            &lt;iframe width="440" height="260" src="https://www.youtube.com/embed/0iAGrdITIiE?wmode=transparent&amp;amp;start=0" frameborder="0" allowfullscreen=""&gt;&lt;/iframe&gt;
  181.            &lt;figcaption&gt;&lt;span class="caption"&gt;Spacecraft can fly by a planet to get a boost using gravity.&lt;/span&gt;&lt;/figcaption&gt;
  182.          &lt;/figure&gt;
  183.  
  184. &lt;p&gt;&lt;a href="https://www.esa.int/Science_Exploration/Space_Science/BepiColombo"&gt;BepiColombo&lt;/a&gt;, a joint mission by ESA and the Japan Aerospace Exploration Agency, JAXA, will make its sixth flyby of Mercury in January 2025. This maneuver will help the spacecraft enter orbit around Mercury by November 2026. BepiColombo aims to study Mercury’s composition, atmosphere and surface geology. &lt;/p&gt;
  185.  
  186. &lt;p&gt;NASA’s &lt;a href="https://science.nasa.gov/mission/europa-clipper/"&gt;Europa Clipper&lt;/a&gt; mission, which launched in October 2024, will make significant progress on its journey to &lt;a href="https://theconversation.com/jupiters-moons-hide-giant-subsurface-oceans-europa-clipper-is-one-of-2-missions-on-their-way-to-see-if-these-moons-could-support-life-203207"&gt;Jupiter’s moon Europa&lt;/a&gt;. In March 2025, the spacecraft will perform a flyby maneuver at Mars. &lt;/p&gt;
  187.  
  188. &lt;p&gt;This maneuver will help the spacecraft gain the necessary speed and trajectory for its long voyage. Later in December 2026, Europa Clipper will perform a flyby of Earth, using Earth’s gravity to further increase its momentum so it can arrive at Europa in April 2030.&lt;/p&gt;
  189.  
  190. &lt;p&gt;The ESA’s &lt;a href="https://www.heramission.space/"&gt;Hera mission&lt;/a&gt; will also perform a flyby of Mars in March 2025. Hera is part of the &lt;a href="https://www.esa.int/Space_Safety/Hera/Asteroid_Impact_Deflection_Assessment_AIDA_collaboration"&gt;Asteroid Impact and Deflection Assessment&lt;/a&gt; mission, which plans to study the Didymos binary asteroid system. The mission will provide valuable data on asteroid deflection techniques and contribute to planetary defense strategies.&lt;/p&gt;
  191.  
  192. &lt;p&gt;&lt;a href="https://science.nasa.gov/mission/lucy/"&gt;NASA’s Lucy&lt;/a&gt; mission will continue its journey to explore the Jupiter Trojan asteroids, which share Jupiter’s orbit around the Sun, in 2025. One key event for Lucy is its flyby of the inner main-belt &lt;a href="https://www.spacereference.org/asteroid/52246-donaldjohanson-1981-eq5"&gt;asteroid 52246 Donaldjohanson&lt;/a&gt;, scheduled for April 20, 2025. &lt;/p&gt;
  193.  
  194. &lt;p&gt;This flyby will provide valuable data on this ancient asteroid’s composition and surface features, which can help researchers gain insights into the early solar system. The asteroid is named after the paleoanthropologist who discovered the famous &lt;a href="https://www.nhm.ac.uk/discover/australopithecus-afarensis-lucy-species.html"&gt;“Lucy” fossil&lt;/a&gt;.&lt;/p&gt;
  195.  
  196. &lt;p&gt;ESA’s &lt;a href="https://www.esa.int/Science_Exploration/Space_Science/Juice"&gt;Jupiter Icy Moons Explorer&lt;/a&gt;, or JUICE, mission will perform a Venus flyby in August 2025. This maneuver will help JUICE gain the necessary speed and trajectory for its journey to Jupiter. Once it arrives, JUICE will study &lt;a href="https://theconversation.com/jupiters-moons-hide-giant-subsurface-oceans-europa-clipper-is-one-of-2-missions-on-their-way-to-see-if-these-moons-could-support-life-203207"&gt;Jupiter’s icy moons&lt;/a&gt; to understand their potential for harboring life.&lt;/p&gt;
  197.  
  198. &lt;p&gt;2025 promises to be a groundbreaking year for space exploration. With NASA’s ambitious missions and significant contributions from other countries, we are set to make remarkable strides in humanity’s understanding of the universe. These missions will not only advance scientific knowledge but also inspire future generations to look to the stars.&lt;/p&gt;&lt;img src="https://counter.theconversation.com/content/243645/count.gif" alt="The Conversation" width="1" height="1" /&gt;
  199. &lt;p class="fine-print"&gt;&lt;em&gt;&lt;span&gt;Zhenbo Wang receives funding from NASA.&lt;/span&gt;&lt;/em&gt;&lt;/p&gt;</content>
  200.    <summary>From exploring the Moon to revealing mysteries of the solar system, space agencies around the world are gearing up for an exciting year of launches and flybys.</summary>
  201.    <author>
  202.      <name>Zhenbo Wang, Associate Professor of Mechanical, Aerospace and Biomedical Engineering, University of Tennessee</name>
  203.      <foaf:homepage rdf:resource="https://theconversation.com/profiles/zhenbo-wang-2259732"/>
  204.    </author>
  205.    <rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
  206.  </entry>
  207.  <entry>
  208.    <id>tag:theconversation.com,2011:article/243592</id>
  209.    <published>2024-12-24T21:31:03Z</published>
  210.    <updated>2024-12-24T21:31:03Z</updated>
  211.    <link rel="alternate" type="text/html" href="https://theconversation.com/from-dead-galaxies-to-mysterious-red-dots-heres-what-the-james-webb-telescope-has-found-in-just-3-years-243592"/>
  212.    <title>From dead galaxies to mysterious red dots, here’s what the James Webb telescope has found in just 3 years</title>
  213.    <content type="html">&lt;figure&gt;&lt;img src="https://images.theconversation.com/files/637454/original/file-20241210-15-ib72mn.png?ixlib=rb-4.1.0&amp;amp;rect=11%2C11%2C1944%2C1101&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=496&amp;amp;fit=clip" /&gt;&lt;figcaption&gt;&lt;span class="caption"&gt;Dust in the heart of galaxy NGC628.&lt;/span&gt; &lt;span class="attribution"&gt;&lt;a class="source" href="https://www.flickr.com/photos/geckzilla/52225123182/"&gt;NASA / ESA / CSA / Judy Schmidt&lt;/a&gt;, &lt;a class="license" href="http://creativecommons.org/licenses/by/4.0/"&gt;CC BY&lt;/a&gt;&lt;/span&gt;&lt;/figcaption&gt;&lt;/figure&gt;&lt;p&gt;On this day three years ago, we witnessed &lt;a href="https://www.nhm.ac.uk/discover/news/2021/december/james-webb-telescope-launched-view-early-universe.html"&gt;the nail-biting launch&lt;/a&gt; of the James Webb Space Telescope (JWST), the largest and most powerful telescope humans have ever sent into space.&lt;/p&gt;
  214.  
  215. &lt;p&gt;It took 30 years to build, but in three short years of operation, JWST has already revolutionised our view of the cosmos.&lt;/p&gt;
  216.  
  217. &lt;p&gt;It’s explored our own Solar System, studied the atmospheres of distant planets in search of signs of life and probed the farthest depths to find the very first stars and galaxies formed in the universe.&lt;/p&gt;
  218.  
  219. &lt;p&gt;Here’s what JWST has taught us about the early universe since its launch – and the new mysteries it has uncovered.&lt;/p&gt;
  220.  
  221. &lt;h2&gt;Eerie blue monsters&lt;/h2&gt;
  222.  
  223. &lt;p&gt;JWST has pushed the boundary of how far we can look into the universe to find the first stars and galaxies. With Earth’s atmosphere out of the way, its location in space makes for perfect conditions to peer into the depths of the cosmos with infrared light.&lt;/p&gt;
  224.  
  225. &lt;p&gt;The current record for the most distant galaxy confirmed by JWST dates back to a time when the universe &lt;a href="https://www.nature.com/articles/s41586-024-07860-9"&gt;was only about 300 million years old&lt;/a&gt;. Surprisingly, within this short time window, this galaxy managed to form about 400 million times the mass of our Sun. &lt;/p&gt;
  226.  
  227. &lt;p&gt;This indicates star formation in the early universe was extremely efficient. And this galaxy is not the only one.&lt;/p&gt;
  228.  
  229. &lt;p&gt;When galaxies grow, their stars explode, creating dust. The bigger the galaxy, the more dust it has. This dust makes galaxies appear red because it absorbs the blue light. But here’s the catch: JWST has shown these first galaxies to be shockingly bright, massive &lt;a href="https://academic.oup.com/mnras/article/522/3/3986/7156962"&gt;and very blue&lt;/a&gt;, with no sign of any dust. That’s a real puzzle.&lt;/p&gt;
  230.  
  231. &lt;p&gt;There are many theories to explain the weird nature of these first galaxies. Do they have huge stars that just collapse due to gravity without undergoing massive supernova explosions?&lt;/p&gt;
  232.  
  233. &lt;p&gt;Or do they have such large explosions that all dust is pushed away far from the galaxy, exposing a blue, dust-free core? Perhaps the dust is destroyed due to the intense radiation from these early exotic stars – we just don’t know yet.&lt;/p&gt;
  234.  
  235. &lt;figure&gt;
  236.            &lt;iframe width="440" height="260" src="https://www.youtube.com/embed/I0YXNV5TuVU?wmode=transparent&amp;amp;start=0" frameborder="0" allowfullscreen=""&gt;&lt;/iframe&gt;
  237.            &lt;figcaption&gt;&lt;span class="caption"&gt;Artist’s impression of what a blue galaxy in the early universe would look like. ESO/M. Kornmesser.&lt;/span&gt;&lt;/figcaption&gt;
  238.          &lt;/figure&gt;
  239.  
  240. &lt;h2&gt;Unusual chemistry in early galaxies&lt;/h2&gt;
  241.  
  242. &lt;p&gt;The early stars were the key building blocks of what eventually became life. The universe began with only hydrogen, helium and a small amount of lithium. All other elements, from the calcium in our bones to the oxygen in the air we breathe, were forged in the cores of these stars.&lt;/p&gt;
  243.  
  244. &lt;p&gt;JWST has discovered that &lt;a href="https://iopscience.iop.org/article/10.3847/1538-4357/ad5f88"&gt;early galaxies also have unusual chemical features&lt;/a&gt;. &lt;/p&gt;
  245.  
  246. &lt;p&gt;They contain a significant amount of nitrogen, far more than what we observe in our Sun, while most other metals are present in lower quantities. This suggests there were processes at play in the early universe we don’t yet fully understand.&lt;/p&gt;
  247.  
  248. &lt;p&gt;JWST has shown our models of how stars drive the chemical evolution of galaxies are still incomplete, meaning we still don’t fully understand the conditions that led to our existence.&lt;/p&gt;
  249.  
  250. &lt;figure class="align-center zoomable"&gt;
  251.            &lt;a href="https://images.theconversation.com/files/636987/original/file-20241208-15-6a25qy.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=1000&amp;amp;fit=clip"&gt;&lt;img alt="A small image of a telescope with charts of chemical elements on the right side." src="https://images.theconversation.com/files/636987/original/file-20241208-15-6a25qy.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;fit=clip" srcset="https://images.theconversation.com/files/636987/original/file-20241208-15-6a25qy.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=151&amp;amp;fit=crop&amp;amp;dpr=1 600w, https://images.theconversation.com/files/636987/original/file-20241208-15-6a25qy.png?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=151&amp;amp;fit=crop&amp;amp;dpr=2 1200w, https://images.theconversation.com/files/636987/original/file-20241208-15-6a25qy.png?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=151&amp;amp;fit=crop&amp;amp;dpr=3 1800w, https://images.theconversation.com/files/636987/original/file-20241208-15-6a25qy.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=190&amp;amp;fit=crop&amp;amp;dpr=1 754w, https://images.theconversation.com/files/636987/original/file-20241208-15-6a25qy.png?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=190&amp;amp;fit=crop&amp;amp;dpr=2 1508w, https://images.theconversation.com/files/636987/original/file-20241208-15-6a25qy.png?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=190&amp;amp;fit=crop&amp;amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"&gt;&lt;/a&gt;
  252.            &lt;figcaption&gt;
  253.              &lt;span class="caption"&gt;Different chemical elements observed in one of the first galaxies in the universe uncovered by JWST.&lt;/span&gt;
  254.              &lt;span class="attribution"&gt;&lt;a class="source" href="https://iopscience.iop.org/article/10.3847/1538-4357/ad5f88"&gt;Adapted from Castellano et al., 2024 The Astrophysical Journal; JWST-GLASS and UNCOVER Teams&lt;/a&gt;&lt;/span&gt;
  255.            &lt;/figcaption&gt;
  256.          &lt;/figure&gt;
  257.  
  258. &lt;h2&gt;Small things that ended the cosmic dark arges&lt;/h2&gt;
  259.  
  260. &lt;p&gt;Using massive clusters of galaxies as gigantic magnifying glasses, JWST’s sensitive cameras can also peer deep into the cosmos &lt;a href="https://www.nature.com/articles/s41586-024-07043-6"&gt;to find the faintest galaxies&lt;/a&gt;.&lt;/p&gt;
  261.  
  262. &lt;p&gt;We pushed further to find the point at which galaxies become so faint, they stop forming stars altogether. This helps us understand the conditions under which galaxy formation comes to an end.&lt;/p&gt;
  263.  
  264. &lt;p&gt;JWST is yet to find this limit. However, it has uncovered many faint galaxies, far more than anticipated, emitting over four times the energetic photons (light particles) we expected.  &lt;/p&gt;
  265.  
  266. &lt;p&gt;The discovery suggests these small galaxies may have played a crucial role in &lt;a href="https://en.wikipedia.org/wiki/Reionization"&gt;ending the cosmic “dark ages”&lt;/a&gt; not long after the Big Bang.&lt;/p&gt;
  267.  
  268. &lt;figure class="align-center zoomable"&gt;
  269.            &lt;a href="https://images.theconversation.com/files/637057/original/file-20241209-17-4fhpox.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=1000&amp;amp;fit=clip"&gt;&lt;img alt="The faintest galaxies uncovered by JWST in the early cosmos." src="https://images.theconversation.com/files/637057/original/file-20241209-17-4fhpox.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;fit=clip" srcset="https://images.theconversation.com/files/637057/original/file-20241209-17-4fhpox.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=150&amp;amp;fit=crop&amp;amp;dpr=1 600w, https://images.theconversation.com/files/637057/original/file-20241209-17-4fhpox.png?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=150&amp;amp;fit=crop&amp;amp;dpr=2 1200w, https://images.theconversation.com/files/637057/original/file-20241209-17-4fhpox.png?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=150&amp;amp;fit=crop&amp;amp;dpr=3 1800w, https://images.theconversation.com/files/637057/original/file-20241209-17-4fhpox.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=188&amp;amp;fit=crop&amp;amp;dpr=1 754w, https://images.theconversation.com/files/637057/original/file-20241209-17-4fhpox.png?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=188&amp;amp;fit=crop&amp;amp;dpr=2 1508w, https://images.theconversation.com/files/637057/original/file-20241209-17-4fhpox.png?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=188&amp;amp;fit=crop&amp;amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"&gt;&lt;/a&gt;
  270.            &lt;figcaption&gt;
  271.              &lt;span class="caption"&gt;Rectangles highlight the apertures of JWST’s near infrared spectrograph array, through which light was captured and analysed to unravel the mysteries of the galaxies’ chemical compositions.&lt;/span&gt;
  272.              &lt;span class="attribution"&gt;&lt;a class="source" href="https://www.nature.com/articles/s41586-024-07043-6"&gt;Atek et al., 2024, Nature&lt;/a&gt;&lt;/span&gt;
  273.            &lt;/figcaption&gt;
  274.          &lt;/figure&gt;
  275.  
  276. &lt;hr&gt;
  277. &lt;p&gt;
  278.  &lt;em&gt;
  279.    &lt;strong&gt;
  280.      Read more:
  281.      &lt;a href="https://theconversation.com/what-ended-the-dark-ages-in-the-early-universe-new-webb-data-just-brought-us-closer-to-solving-the-mystery-224525"&gt;What ended the 'dark ages' in the early universe? New Webb data just brought us closer to solving the mystery&lt;/a&gt;
  282.    &lt;/strong&gt;
  283.  &lt;/em&gt;
  284. &lt;/p&gt;
  285. &lt;hr&gt;
  286.  
  287.  
  288. &lt;h2&gt;The mysterious case of the little red dots&lt;/h2&gt;
  289.  
  290. &lt;p&gt;The very first images of JWST resulted in another dramatic, unexpected discovery. The early universe is inhabited by an abundance of “&lt;a href="https://en.wikipedia.org/wiki/Little_red_dot_(galaxy)"&gt;little red dots&lt;/a&gt;”: extremely compact red colour sources of unknown origin.&lt;/p&gt;
  291.  
  292. &lt;p&gt;Initially, they were thought to be &lt;a href="https://theconversation.com/we-just-discovered-the-impossible-how-giant-baby-galaxies-are-shaking-up-our-understanding-of-the-early-universe-200343"&gt;massive super-dense galaxies that shouldn’t be possible&lt;/a&gt;, but detailed observations in the past year have revealed a combination of deeply puzzling and contradictory properties.&lt;/p&gt;
  293.  
  294. &lt;p&gt;Bright hydrogen gas is emitting light at enormous speeds, thousands of kilometres per second, characteristic of gas swirling around a supermassive black hole.&lt;/p&gt;
  295.  
  296. &lt;p&gt;This phenomenon, called an active galactic nucleus, usually indicates a &lt;a href="https://theconversation.com/the-brightest-object-in-the-universe-is-a-black-hole-that-eats-a-star-a-day-222612"&gt;feeding frenzy&lt;/a&gt; where a supermassive black hole is gobbling up all the gas around it, growing rapidly.&lt;/p&gt;
  297.  
  298. &lt;p&gt;But these are not your garden variety active galactic nuclei. For starters: they don’t emit any detectable X-rays, as is normally expected. Even more intriguingly, they seem to have the features of star populations.&lt;/p&gt;
  299.  
  300. &lt;p&gt;Could these galaxies be both stars and active galactic nuclei at the same time? Or some evolutionary stage in between? Whatever they are, the little red dots are probably going to teach us something about the birth of both supermassive black holes and stars in galaxies.&lt;/p&gt;
  301.  
  302. &lt;figure class="align-center zoomable"&gt;
  303.            &lt;a href="https://images.theconversation.com/files/637044/original/file-20241209-15-uikjjz.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=1000&amp;amp;fit=clip"&gt;&lt;img alt="An image of galaxies with several red ones highlighted in a series of boxes." src="https://images.theconversation.com/files/637044/original/file-20241209-15-uikjjz.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;fit=clip" srcset="https://images.theconversation.com/files/637044/original/file-20241209-15-uikjjz.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=286&amp;amp;fit=crop&amp;amp;dpr=1 600w, https://images.theconversation.com/files/637044/original/file-20241209-15-uikjjz.png?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=286&amp;amp;fit=crop&amp;amp;dpr=2 1200w, https://images.theconversation.com/files/637044/original/file-20241209-15-uikjjz.png?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=286&amp;amp;fit=crop&amp;amp;dpr=3 1800w, https://images.theconversation.com/files/637044/original/file-20241209-15-uikjjz.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=360&amp;amp;fit=crop&amp;amp;dpr=1 754w, https://images.theconversation.com/files/637044/original/file-20241209-15-uikjjz.png?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=360&amp;amp;fit=crop&amp;amp;dpr=2 1508w, https://images.theconversation.com/files/637044/original/file-20241209-15-uikjjz.png?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=360&amp;amp;fit=crop&amp;amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"&gt;&lt;/a&gt;
  304.            &lt;figcaption&gt;
  305.              &lt;span class="caption"&gt;In the background, the JWST image of the Pandora Cluster (Abell 2744) is displayed, with a little red dot highlighted in a blue inset. The foreground inset on the left showcases a montage of several little red dots discovered by JWST.&lt;/span&gt;
  306.              &lt;span class="attribution"&gt;&lt;span class="source"&gt;Adapted from Furtak et al., and Matthee et al.,  The Astrophysical Journal, 2023-2024;  JWST-GLASS and UNCOVER Teams&lt;/span&gt;&lt;/span&gt;
  307.            &lt;/figcaption&gt;
  308.          &lt;/figure&gt;
  309.  
  310. &lt;h2&gt;The impossibly early galaxies&lt;/h2&gt;
  311.  
  312. &lt;p&gt;As well as extremely lively early galaxies, &lt;a href="https://www.nature.com/articles/s41586-024-07191-9"&gt;JWST has also found extremely dead corpses&lt;/a&gt;: galaxies in the early universe that are relics of intense star formation at cosmic dawn.&lt;/p&gt;
  313.  
  314. &lt;p&gt;These corpses had been found by Hubble and ground-based telescopes, but only JWST had the power to dissect their light to reveal how long they’ve been dead.&lt;/p&gt;
  315.  
  316. &lt;p&gt;It has uncovered some extremely massive galaxies (as massive as our Milky Way today and more) that formed in the first 700 million years of cosmic history. Our current galaxy formation models can’t explain these objects – they are too big and formed too early.&lt;/p&gt;
  317.  
  318. &lt;p&gt;Cosmologists are still debating whether the models can be bent to fit (for example, maybe early star formation was extremely efficient) or whether we have to reconsider the nature of dark matter and how it gives rise to early collapsing objects.&lt;/p&gt;
  319.  
  320. &lt;p&gt;JWST will turn up many more of these objects in the next year and study the existing ones in greater detail. Either way, we will know soon.&lt;/p&gt;
  321.  
  322.  
  323.  
  324. &lt;h2&gt;What’s next for JWST?&lt;/h2&gt;
  325.  
  326. &lt;p&gt;Just within its first steps, the telescope has revealed many shortcomings of our current models of the universe. While we are refining our models to account for the updates JWST has brought us, we are most excited about the unknown unknowns.&lt;/p&gt;
  327.  
  328. &lt;p&gt;The mysterious red dots were hiding from our view. What else is lingering in the depths of cosmos? JWST will soon tell us. &lt;/p&gt;
  329.  
  330. &lt;hr&gt;
  331. &lt;p&gt;
  332.  &lt;em&gt;
  333.    &lt;strong&gt;
  334.      Read more:
  335.      &lt;a href="https://theconversation.com/10-times-this-year-the-webb-telescope-blew-us-away-with-new-images-of-our-stunning-universe-194739"&gt;10 times this year the Webb telescope blew us away with new images of our stunning universe&lt;/a&gt;
  336.    &lt;/strong&gt;
  337.  &lt;/em&gt;
  338. &lt;/p&gt;
  339. &lt;hr&gt;
  340. &lt;img src="https://counter.theconversation.com/content/243592/count.gif" alt="The Conversation" width="1" height="1" /&gt;
  341. &lt;p class="fine-print"&gt;&lt;em&gt;&lt;span&gt;Themiya Nanayakkara receives funding from Australian Research Council Laureate Fellowship.&lt;/span&gt;&lt;/em&gt;&lt;/p&gt;&lt;p class="fine-print"&gt;&lt;em&gt;&lt;span&gt;Ivo Labbe receives funding from Australian Research Council in the form of a Future Fellowship.&lt;/span&gt;&lt;/em&gt;&lt;/p&gt;&lt;p class="fine-print"&gt;&lt;em&gt;&lt;span&gt;Karl Glazebrook receives funding from the Australian Research Council for a Laureate Fellowship for JWST research  and from the Australian Space Agency for JWST training activities. &lt;/span&gt;&lt;/em&gt;&lt;/p&gt;</content>
  342.    <summary>The James Webb Space Telescope is celebrating three years from its launch. Its discoveries have already changed our understanding of the early universe.</summary>
  343.    <author>
  344.      <name>Themiya Nanayakkara, Scientist at the James Webb Australian Data Centre, Swinburne University of Technology</name>
  345.      <foaf:homepage rdf:resource="https://theconversation.com/profiles/themiya-nanayakkara-1324058"/>
  346.    </author>
  347.    <author>
  348.      <name>Ivo Labbe, ARC Future Fellow / Associate Professor, Swinburne University of Technology</name>
  349.      <foaf:homepage rdf:resource="https://theconversation.com/profiles/ivo-labbe-1416844"/>
  350.    </author>
  351.    <author>
  352.      <name>Karl Glazebrook, ARC Laureate Fellow &amp; Distinguished Professor, Centre for Astrophysics &amp; Supercomputing, Swinburne University of Technology</name>
  353.      <foaf:homepage rdf:resource="https://theconversation.com/profiles/karl-glazebrook-6792"/>
  354.    </author>
  355.    <rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
  356.  </entry>
  357.  <entry>
  358.    <id>tag:theconversation.com,2011:article/245321</id>
  359.    <published>2024-12-20T13:17:13Z</published>
  360.    <updated>2024-12-20T13:17:13Z</updated>
  361.    <link rel="alternate" type="text/html" href="https://theconversation.com/in-disneys-moana-the-characters-navigate-using-the-stars-just-like-real-polynesian-explorers-an-astronomer-explains-how-these-methods-work-245321"/>
  362.    <title>In Disney’s ‘Moana,’ the characters navigate using the stars, just like real Polynesian explorers − an astronomer explains how these methods work</title>
  363.    <content type="html">&lt;figure&gt;&lt;img src="https://images.theconversation.com/files/639252/original/file-20241217-17-7i1pcj.jpg?ixlib=rb-4.1.0&amp;amp;rect=89%2C10%2C3434%2C1130&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=496&amp;amp;fit=clip" /&gt;&lt;figcaption&gt;&lt;span class="caption"&gt;Wayfarers around the world have used the stars to navigate the sea. &lt;/span&gt; &lt;span class="attribution"&gt;&lt;a class="source" href="https://www.gettyimages.com/detail/photo/panoramic-image-of-sunset-over-sea-with-silhouette-royalty-free-image/1465242737"&gt;Wirestock/iStock via Getty Images Plus&lt;/a&gt;&lt;/span&gt;&lt;/figcaption&gt;&lt;/figure&gt;&lt;p&gt;If you have visited an island like one of the Hawaiian Islands, Tahiti or Easter Island, also known as Rapa Nui, you may have noticed how small these land masses appear against the vast Pacific Ocean. If you’re on Hawaii, the nearest island to you is more than 1,000 miles (1,600 kilometers) away, and the coast of the continental United States is more than 2,000 miles (3,200 kilometers) away. To say these islands are secluded is an understatement. &lt;/p&gt;
  364.  
  365. &lt;p&gt;For me, watching &lt;a href="https://www.smithsonianmag.com/smithsonian-institution/how-story-moana-and-maui-holds-against-cultural-truths-180961258/"&gt;the movie “Moana&lt;/a&gt;” in 2016 was eye-opening. I knew that &lt;a href="https://nzhistory.govt.nz/culture/encounters/polynesian-voyaging"&gt;Polynesian people traveled&lt;/a&gt; between a number of Pacific islands, but seeing Moana set sail on a canoe made me realize exactly how small those boats are compared with what must have seemed like an endless ocean. Yet our fictional hero went on this journey anyway, like the countless real-life Polynesian voyagers upon which she is based. &lt;/p&gt;
  366.  
  367. &lt;figure class="align-center zoomable"&gt;
  368.            &lt;a href="https://images.theconversation.com/files/637902/original/file-20241211-15-ucnjcn.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=1000&amp;amp;fit=clip"&gt;&lt;img alt="Oceania as shown from the ISS" src="https://images.theconversation.com/files/637902/original/file-20241211-15-ucnjcn.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;fit=clip" srcset="https://images.theconversation.com/files/637902/original/file-20241211-15-ucnjcn.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=400&amp;amp;fit=crop&amp;amp;dpr=1 600w, https://images.theconversation.com/files/637902/original/file-20241211-15-ucnjcn.jpg?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=400&amp;amp;fit=crop&amp;amp;dpr=2 1200w, https://images.theconversation.com/files/637902/original/file-20241211-15-ucnjcn.jpg?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=400&amp;amp;fit=crop&amp;amp;dpr=3 1800w, https://images.theconversation.com/files/637902/original/file-20241211-15-ucnjcn.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=503&amp;amp;fit=crop&amp;amp;dpr=1 754w, https://images.theconversation.com/files/637902/original/file-20241211-15-ucnjcn.jpg?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=503&amp;amp;fit=crop&amp;amp;dpr=2 1508w, https://images.theconversation.com/files/637902/original/file-20241211-15-ucnjcn.jpg?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=503&amp;amp;fit=crop&amp;amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"&gt;&lt;/a&gt;
  369.            &lt;figcaption&gt;
  370.              &lt;span class="caption"&gt;Islands in Polynesia can be thousands of miles apart.&lt;/span&gt;
  371.              &lt;span class="attribution"&gt;&lt;a class="source" href="https://www.nasa.gov/image-article/south-pacific-ocean-pictured-from-space-station/"&gt;NASA&lt;/a&gt;&lt;/span&gt;
  372.            &lt;/figcaption&gt;
  373.          &lt;/figure&gt;
  374.  
  375. &lt;p&gt;&lt;a href="https://science.psu.edu/astro/people/cxp137"&gt;As an astronomer&lt;/a&gt;, I have been teaching college students and visitors to our planetarium how to find stars in our sky for more than 20 years. As part of teaching appreciation for the beauty of the sky and the stars, I want to help people understand that if you know the stars well, you can never get lost. &lt;/p&gt;
  376.  
  377. &lt;p&gt;U.S. Navy veterans learned the stars in their navigation courses, and European cultures used the stars to navigate, but the techniques of Polynesian wayfinding shown in Moana brought these ideas to a very wide audience.  &lt;/p&gt;
  378.  
  379. &lt;p&gt;The movie Moana gave me a new hook – pun not intended – for my planetarium shows and lessons on how to locate objects in the night sky. With “&lt;a href="https://www.imdb.com/title/tt13622970/"&gt;Moana 2&lt;/a&gt;” out now, I am excited to see even more astronomy on the big screen and to figure out how I can build new lessons using the ideas in the movie.&lt;/p&gt;
  380.  
  381. &lt;h2&gt;The North Star&lt;/h2&gt;
  382.  
  383. &lt;p&gt;Have you ever found the North Star, Polaris, in your sky? I try to spot it every time I am out observing, and I teach visitors at my shows to use the &lt;a href="https://coolcosmos.ipac.caltech.edu/ask/253-How-can-I-find-the-North-Star"&gt;“pointer stars” in the bowl of the Big Dipper&lt;/a&gt; to find it. These two stars in the Big Dipper point you directly to Polaris.&lt;/p&gt;
  384.  
  385.  
  386.  
  387. &lt;p&gt;If you are facing Polaris, then you know you are facing north. Polaris is special because it is &lt;a href="https://science.nasa.gov/solar-system/skywatching/what-is-the-north-star-and-how-do-you-find-it/"&gt;almost directly above Earth’s North Pole&lt;/a&gt;, and so everyone north of the equator can see it year-round in exactly the same spot in their sky. &lt;/p&gt;
  388.  
  389. &lt;p&gt;It’s a key star for navigation because if you measure its height above your horizon, that tells you how far you are north of Earth’s equator. For the large number of people who live near 40 degrees north of the equator, you will see Polaris about 40 degrees above your horizon. &lt;/p&gt;
  390.  
  391. &lt;p&gt;If you live in northern Canada, Polaris will appear higher in your sky, and if you live closer to the equator, Polaris will appear closer to the horizon. The other stars and constellations come and go with the seasons, though, so what you see opposite Polaris in the sky will change every month. &lt;/p&gt;
  392.  
  393. &lt;figure&gt;
  394.            &lt;iframe width="440" height="260" src="https://www.youtube.com/embed/COHwfKusGbs?wmode=transparent&amp;amp;start=0" frameborder="0" allowfullscreen=""&gt;&lt;/iframe&gt;
  395.            &lt;figcaption&gt;&lt;span class="caption"&gt;Look for the Big Dipper to find the North Star, Polaris.&lt;/span&gt;&lt;/figcaption&gt;
  396.          &lt;/figure&gt;
  397.  
  398. &lt;p&gt;You can use all of the stars to navigate, but to do that you need to know where to find them on every night of the year and at every hour of the night. So, navigating with stars other than Polaris is more complicated to learn.&lt;/p&gt;
  399.  
  400. &lt;h2&gt;Maui’s fishhook&lt;/h2&gt;
  401.  
  402. &lt;p&gt;At the end of June, around 11 p.m., a bright red star might catch your eye if you look directly opposite from Polaris. This is the star &lt;a href="https://www.skyatnightmagazine.com/advice/antares"&gt;Antares&lt;/a&gt;, and it is the brightest star in the constellation Scorpius, the Scorpion. &lt;/p&gt;
  403.  
  404. &lt;p&gt;If you are a “Moana” fan like me and the others in my family, though, you may know this group of stars by a different name – &lt;a href="http://www.hawastsoc.org/deepsky/sco/"&gt;Maui’s fishhook&lt;/a&gt;. &lt;/p&gt;
  405.  
  406. &lt;p&gt;If you are in the Northern Hemisphere, Scorpius may not fully appear above your horizon, but if you are on a Polynesian island, you should see all of the constellation rising in the southeast, hitting its highest point in the sky when it is due south, and setting in the southwest. &lt;/p&gt;
  407.  
  408.  
  409.  
  410. &lt;p&gt;Astronomers and navigators can measure latitude using the height of the stars, which Maui and Moana did in the movie &lt;a href="https://www.skyatnightmagazine.com/advice/diy/build-tool-for-measuring-sky"&gt;using their hands as measuring tools&lt;/a&gt;. &lt;/p&gt;
  411.  
  412. &lt;p&gt;The easiest way to do this is to figure out how high Polaris is above your horizon. If you can’t see it at all, you must be south of the equator, but if you see Polaris 5 degrees (the width of three fingers at arm’s length) or 10 degrees above your horizon (the width of your full fist held at arm’s length), then you are 5 degrees or 10 degrees north of the equator. &lt;/p&gt;
  413.  
  414. &lt;p&gt;The other stars, like those in Maui’s fishhook, will appear to rise, set and hit their highest point at different locations in the sky depending on where you are on the Earth. &lt;/p&gt;
  415.  
  416. &lt;p&gt;Polynesian navigators &lt;a href="https://manoa.hawaii.edu/exploringourfluidearth/physical/navigation-and-transportation/wayfinding-and-navigation"&gt;memorized where these stars would appear&lt;/a&gt; in the sky from the different islands they sailed between, and so by looking for those stars in the sky at night, they could determine which direction to sail and for how long to travel across the ocean.&lt;/p&gt;
  417.  
  418. &lt;p&gt;Today, most people just pull out their phones and use the built-in GPS as a guide. Ever since “Moana” was in theaters, I see a completely different reaction to my planetarium talks about using the stars for navigation. By accurately showing how Polynesian navigators used the stars to sail across the ocean, Moana helps even those of us who have never sailed at night to understand the methods of celestial navigation.&lt;/p&gt;
  419.  
  420. &lt;p&gt;The first “Moana” movie came out when my son was 3 years old, and he took an instant liking to the songs, the story and the scenery. There are many jokes about parents who dread having to watch a child’s favorite over and over again, but in my case, I fell in love with the movie too.&lt;/p&gt;
  421.  
  422. &lt;p&gt;Since then, I have wanted to thank the storytellers who made this movie for being so careful to show the astronomy of navigation correctly. I also appreciated that they showed how Polynesian voyagers used the stars and other clues, such as ocean currents, to sail across the huge Pacific Ocean and land safely on a very small island thousands of miles from their home.&lt;/p&gt;&lt;img src="https://counter.theconversation.com/content/245321/count.gif" alt="The Conversation" width="1" height="1" /&gt;
  423. &lt;p class="fine-print"&gt;&lt;em&gt;&lt;span&gt;Christopher Palma does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.&lt;/span&gt;&lt;/em&gt;&lt;/p&gt;</content>
  424.    <summary>Disney’s ‘Moana’ movies have brought a new level of excitement for astronomy and wayfinding, says an astronomer who regularly hosts planetarium shows.</summary>
  425.    <author>
  426.      <name>Christopher Palma, Teaching Professor, Department of Astronomy &amp; Astrophysics, Penn State</name>
  427.      <foaf:homepage rdf:resource="https://theconversation.com/profiles/christopher-palma-314031"/>
  428.    </author>
  429.    <rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
  430.  </entry>
  431.  <entry>
  432.    <id>tag:theconversation.com,2011:article/244915</id>
  433.    <published>2024-12-16T19:08:29Z</published>
  434.    <updated>2024-12-16T19:08:29Z</updated>
  435.    <link rel="alternate" type="text/html" href="https://theconversation.com/when-you-wish-upon-a-star-is-it-already-dead-an-astronomer-crunches-the-numbers-244915"/>
  436.    <title>When you wish upon a star, is it already dead? An astronomer crunches the numbers</title>
  437.    <content type="html">&lt;figure&gt;&lt;img src="https://images.theconversation.com/files/637770/original/file-20241211-15-wvqrzd.jpg?ixlib=rb-4.1.0&amp;amp;rect=0%2C0%2C5760%2C3828&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=496&amp;amp;fit=clip" /&gt;&lt;figcaption&gt;&lt;span class="caption"&gt;&lt;/span&gt; &lt;span class="attribution"&gt;&lt;a class="source" href="http://www.eso.org/public/images/potw1613a/"&gt;ESO/Luis Calçada/Herbert Zodet&lt;/a&gt;, &lt;a class="license" href="http://creativecommons.org/licenses/by/4.0/"&gt;CC BY&lt;/a&gt;&lt;/span&gt;&lt;/figcaption&gt;&lt;/figure&gt;&lt;p&gt;When you wish upon a star, &lt;a href="https://en.wikipedia.org/wiki/When_You_Wish_Upon_a_Star"&gt;Jiminy Cricket told us&lt;/a&gt;, your dreams come true. But according to an idea &lt;a href="https://www.tiktok.com/@robbnwa/video/7379273302432566574"&gt;doing the rounds&lt;/a&gt; on social media, that may not be the case:&lt;/p&gt;
  438.  
  439. &lt;blockquote&gt;
  440. &lt;p&gt;According to astronomy, when you wish upon a star you’re a million years too late. The star is dead, just like your dreams.&lt;/p&gt;
  441. &lt;/blockquote&gt;
  442.  
  443. &lt;p&gt;&lt;div data-react-class="TiktokEmbed" data-react-props="{&amp;quot;url&amp;quot;:&amp;quot;https://www.tiktok.com/@robbnwa/video/7379273302432566574&amp;quot;}"&gt;&lt;/div&gt;&lt;/p&gt;
  444.  
  445. &lt;p&gt;Is that really true? Did Jiminy Cricket lie to us?&lt;/p&gt;
  446.  
  447. &lt;p&gt;As an astronomer, I’m happy to say that the stars we can see in the night sky are a lot closer and live a lot longer than you would think. It’s pretty unlikely you’ve accidentally wished upon a star that’s already dead.&lt;/p&gt;
  448.  
  449. &lt;h2&gt;Stars are closer than you think&lt;/h2&gt;
  450.  
  451. &lt;p&gt;When someone hits you with the depressing factoid that the stars we wish on are already dead, they usually start by saying something about how the stars are “millions of light years away”. This means the light from the star has been travelling for millions of years to reach your eyes, so by now the star is millions of years older and – supposedly – most likely dead.&lt;/p&gt;
  452.  
  453. &lt;p&gt;But the stars you’re wishing on probably aren’t that far away. All the stars we can see with our eyes are inside our galaxy, the Milky Way. The &lt;a href="https://imagine.gsfc.nasa.gov/science/featured_science/milkyway/"&gt;Milky Way is approximately 100,000 light years across&lt;/a&gt;, and our Solar System is about 26,000 light years from the centre of the galaxy. &lt;/p&gt;
  454.  
  455. &lt;p&gt;So if we could see the stars at the very far edge of the galaxy, they’d still only be about 74,000 light years away. That’s nowhere near a million light years away, let alone “millions of light years”.&lt;/p&gt;
  456.  
  457.  
  458.  
  459. &lt;h2&gt;Visible stars are even closer&lt;/h2&gt;
  460.  
  461. &lt;p&gt;In practice, the stars we can see aren’t even that far away. On a dark night, with no Moon and with good vision (which rules me out), the faintest star we can see with our eyes has a brightness of &lt;a href="https://www.atnf.csiro.au/outreach/education/senior/astrophysics/photometry_magnitude.html"&gt;around 6.5 magnitudes&lt;/a&gt;.  &lt;/p&gt;
  462.  
  463. &lt;p&gt;Brighter stars have lower magnitudes, and dimmer stars have higher ones. The brightest star in the Southern Cross has a &lt;a href="https://ui.adsabs.harvard.edu/abs/1993BICDS..43....5T/abstract"&gt;magnitude of 0.8&lt;/a&gt; while the faintest star in the Southern Cross has a &lt;a href="http://simbad.cds.unistra.fr/simbad/sim-id?Ident=epsilon+crucis&amp;amp;NbIdent=1&amp;amp;Radius=2&amp;amp;Radius.unit=arcmin&amp;amp;submit=submit+id"&gt;magnitude of 3.6&lt;/a&gt;. &lt;/p&gt;
  464.  
  465. &lt;p&gt;The visible brightness limit of 6.5 magnitudes means we can only see stars out to around 10,000 light years from Earth. So if you happen to wish on one of the more distant stars, the light has travelled 10,000 years to hit your eye. &lt;/p&gt;
  466.  
  467. &lt;p&gt;And if we assume wishes travel at the speed of light, it’ll take another 10,000 years to reach the star. So even the most distant visible star is only 20,000 years older by the time your wish reaches it. &lt;/p&gt;
  468.  
  469. &lt;p&gt;So the question is: do stars live longer than 20,000 years?&lt;/p&gt;
  470.  
  471.  
  472.  
  473. &lt;h2&gt;Stars live longer than you think&lt;/h2&gt;
  474.  
  475. &lt;p&gt;The &lt;a href="http://tdc-www.harvard.edu/catalogs/bsc5.html"&gt;Yale Bright Star Catalogue&lt;/a&gt; contains 9,096 stars that are brighter than magnitude 7, roughly the limit of what our eyes can see. Many (40%) of the stars in the catalogue are so-called giant stars, which come in three varieties: normal giants, bright giants and super giants. &lt;/p&gt;
  476.  
  477. &lt;p&gt;The more massive the star, &lt;a href="https://science.nasa.gov/universe/stars/"&gt;the shorter its life&lt;/a&gt;. So these giant stars are here for a good time, not a long time. &lt;/p&gt;
  478.  
  479.  
  480.  
  481. &lt;p&gt;But in astronomy a “good time” is still at least a few hundred thousand years. Much longer than your wish needs to arrive at a star closer than 10,000 light years. &lt;/p&gt;
  482.  
  483. &lt;p&gt;The rest of the visible stars are what are called main sequence (or mid-life) stars and sub-giant stars. These stick around a lot longer, up to a few billion years. So when it comes to wishes, age is just a (really big) number.&lt;/p&gt;
  484.  
  485. &lt;h2&gt;The best stars to wish upon&lt;/h2&gt;
  486.  
  487.  
  488.  
  489. &lt;p&gt;If you’re still feeling a bit nervous about wishing upon a dead star, there are a few safe bets. &lt;/p&gt;
  490.  
  491. &lt;p&gt;Alpha Centauri is the closest star to Earth and the fourth brightest star in the sky. Even better, &lt;a href="https://www.space.com/18090-alpha-centauri-nearest-star-system.html"&gt;it’s actually three stars&lt;/a&gt; and they’re only about four light years away. They’ll definitely last longer than the eight years needed for their light to reach you and your wish to reach them.&lt;/p&gt;
  492.  
  493. &lt;p&gt;The brightest star in the sky, Sirius, is a main sequence star only 8.6 light years away. Epsilon Eridani is &lt;a href="https://science.nasa.gov/resource/double-the-rubble/"&gt;approximately ten light years away&lt;/a&gt;. It’s similar to our Sun and &lt;a href="https://www.aanda.org/articles/aa/abs/2008/35/aa09984-08/aa09984-08.html"&gt;a little under a billion years old&lt;/a&gt;. Since Sirius and Epsilon Eridani are in their mid-life, they still have millions, maybe even billions, of years left to burn.&lt;/p&gt;
  494.  
  495. &lt;p&gt;The safest star to send your wishes to? The Sun! The Sun is only eight light minutes away and it’ll be a main-sequence star for around 5 billion years yet.&lt;/p&gt;
  496.  
  497.  
  498.  
  499. &lt;p&gt;So when you wish upon a star, that star is less than 10,000 light years away and will probably live for at least hundreds of thousands of years, and maybe millions or even billions of years (just like your dreams).&lt;/p&gt;&lt;img src="https://counter.theconversation.com/content/244915/count.gif" alt="The Conversation" width="1" height="1" /&gt;
  500. &lt;p class="fine-print"&gt;&lt;em&gt;&lt;span&gt;Laura Nicole Driessen is a brand ambassador for the Rise &amp;amp; Shine Education Orbit Centre of Imagination.&lt;/span&gt;&lt;/em&gt;&lt;/p&gt;</content>
  501.    <summary>Killjoys on social media say there’s no point wishing on stars because they are already dead – but the naysayers are completely wrong.</summary>
  502.    <author>
  503.      <name>Laura Nicole Driessen, Postdoctoral Researcher in Radio Astronomy, University of Sydney</name>
  504.      <foaf:homepage rdf:resource="https://theconversation.com/profiles/laura-nicole-driessen-892965"/>
  505.    </author>
  506.    <rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
  507.  </entry>
  508.  <entry>
  509.    <id>tag:theconversation.com,2011:article/240412</id>
  510.    <published>2024-12-16T13:13:35Z</published>
  511.    <updated>2024-12-16T13:13:35Z</updated>
  512.    <link rel="alternate" type="text/html" href="https://theconversation.com/how-does-the-international-space-station-orbit-earth-without-burning-up-240412"/>
  513.    <title>How does the International Space Station orbit Earth without burning up?</title>
  514.    <content type="html">&lt;figure&gt;&lt;img src="https://images.theconversation.com/files/628842/original/file-20241030-15-lsj7ed.png?ixlib=rb-4.1.0&amp;amp;rect=0%2C9%2C6048%2C4010&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=496&amp;amp;fit=clip" /&gt;&lt;figcaption&gt;&lt;span class="caption"&gt;The International Space Station orbits Earth. &lt;/span&gt; &lt;span class="attribution"&gt;&lt;a class="source" href="https://www.nasa.gov/international-space-station/"&gt;NASA/Roscosmos&lt;/a&gt;&lt;/span&gt;&lt;/figcaption&gt;&lt;/figure&gt;&lt;figure class="align-left "&gt;
  515.            &lt;img alt="" src="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=237&amp;amp;fit=clip" srcset="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=293&amp;amp;fit=crop&amp;amp;dpr=1 600w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=293&amp;amp;fit=crop&amp;amp;dpr=2 1200w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=293&amp;amp;fit=crop&amp;amp;dpr=3 1800w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=368&amp;amp;fit=crop&amp;amp;dpr=1 754w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=368&amp;amp;fit=crop&amp;amp;dpr=2 1508w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=368&amp;amp;fit=crop&amp;amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"&gt;
  516.            &lt;figcaption&gt;
  517.              &lt;span class="caption"&gt;&lt;/span&gt;
  518.              
  519.            &lt;/figcaption&gt;
  520.          &lt;/figure&gt;
  521.  
  522. &lt;p&gt;&lt;em&gt;&lt;a href="https://theconversation.com/us/topics/curious-kids-us-74795"&gt;Curious Kids&lt;/a&gt; is a series for children of all ages. If you have a question you’d like an expert to answer, send it to &lt;a href="mailto:curiouskidsus@theconversation.com"&gt;CuriousKidsUS@theconversation.com&lt;/a&gt;.&lt;/em&gt;&lt;/p&gt;
  523.  
  524. &lt;hr&gt;
  525.  
  526. &lt;blockquote&gt;
  527. &lt;p&gt;&lt;strong&gt;How is the International Space Station able to orbit without burning up? –  Mateo, age 8, New York, New York&lt;/strong&gt;&lt;/p&gt;
  528. &lt;/blockquote&gt;
  529.  
  530. &lt;hr&gt;
  531.  
  532. &lt;p&gt;Flying through Earth’s orbit are thousands of satellites and two operational space stations, including the International Space Station, which weighs as much as 77 elephants. &lt;a href="https://www.nasa.gov/international-space-station/"&gt;The International Space Station&lt;/a&gt;, or ISS, hosts scientists and researchers from around the world as they contribute to discoveries in medicine, microbiology, Earth and space science, and more. &lt;/p&gt;
  533.  
  534. &lt;p&gt;One of my first jobs in aerospace engineering was working on the ISS, and the ISS remains one of my favorite aerospace systems. I now work at Georgia Tech, where &lt;a href="https://ae.gatech.edu/directory/person/kelly-griendling"&gt;I teach aerospace engineering&lt;/a&gt;.&lt;/p&gt;
  535.  
  536. &lt;p&gt;The ISS travels very quickly around the Earth at 5 miles per second (8 kilometers per second), which means it could fly from Atlanta to London in 14 minutes. But at the same time, small chunks of rock called meteoroids shoot through space and burn up when they hit Earth’s atmosphere. How is it that some objects – such as the International Space Station – orbit the Earth unscathed, while others, such as asteroids, burn up?&lt;/p&gt;
  537.  
  538. &lt;figure&gt;
  539.            &lt;iframe width="440" height="260" src="https://www.youtube.com/embed/xg9R4yykvqU?wmode=transparent&amp;amp;start=0" frameborder="0" allowfullscreen=""&gt;&lt;/iframe&gt;
  540.            &lt;figcaption&gt;&lt;span class="caption"&gt;The ISS moves quickly while it orbits the Earth.&lt;/span&gt;&lt;/figcaption&gt;
  541.          &lt;/figure&gt;
  542.  
  543. &lt;p&gt;To answer why the ISS can stay in orbit for decades unscathed, you first need to understand why some things, such as meteoroids, do burn up when they enter our planet’s atmosphere. &lt;/p&gt;
  544.  
  545. &lt;h2&gt;Why do meteoroids burn up in the atmosphere?&lt;/h2&gt;
  546.  
  547. &lt;p&gt;&lt;a href="https://science.nasa.gov/solar-system/meteors-meteorites/"&gt;Meteoroids are small chunks of rock and metal&lt;/a&gt; that orbit the Sun. These space rocks can travel between 7 and 25 miles per second (12 to 40 km per second). That’s fast enough to cross the entire United States in about 5 minutes. &lt;/p&gt;
  548.  
  549. &lt;p&gt;Sometimes, the orbit of a meteoroid overlaps with Earth, and the meteoroid enters Earth’s atmosphere – where it burns up and disintegrates.&lt;/p&gt;
  550.  
  551. &lt;p&gt;Even though you can’t see them, the atmosphere is full of a combination of particles, primarily nitrogen and oxygen, which make up the air you breathe. The farther you are from the surface of the Earth, the lower the density of particles in the atmosphere. &lt;/p&gt;
  552.  
  553. &lt;p&gt;The &lt;a href="https://scied.ucar.edu/learning-zone/atmosphere/layers-earths-atmosphere"&gt;atmosphere has several layers&lt;/a&gt;. When something from space enters the Earth’s atmosphere, it must pass through each of these layers before it reaches the ground. &lt;/p&gt;
  554.  
  555. &lt;p&gt;&lt;a href="https://sites.wustl.edu/meteoritesite/items/meteors/"&gt;Meteoroids&lt;/a&gt; burn up in a part of Earth’s atmosphere &lt;a href="https://scied.ucar.edu/learning-zone/atmosphere/mesosphere"&gt;called the mesosphere&lt;/a&gt;, which is 30 to 50 miles (48 to 80 kilometers) above the ground. Even though the air is thin up there, meteoroids still bump into air particles as they fly through.  &lt;/p&gt;
  556.  
  557. &lt;p&gt;When meteoroids zoom through the atmosphere at these very high speeds, they are destroyed by a process that causes them to heat up and break apart. The meteoroid pushes the air particles together, kind of like how a bulldozer pushes dirt. This process creates a lot of pressure and heat. The air particles hit the meteoroid &lt;a href="https://science.howstuffworks.com/transport/flight/modern/hypersonic-plane.htm"&gt;at hypersonic speeds&lt;/a&gt; – much faster than the speed of sound – causing atoms to break away and form cracks in the meteroid.&lt;/p&gt;
  558.  
  559. &lt;p&gt;The high pressure and hot air get into the cracks, &lt;a href="https://doi.org/10.1029/2020JA028229"&gt;making the meteoroid break apart&lt;/a&gt; and burn up as it falls through the sky. This process is called &lt;a href="https://www.youtube.com/watch?v=r4roWT1SD2s"&gt;meteoroid ablation&lt;/a&gt; and is what you are actually seeing when you witness a “shooting star.”&lt;/p&gt;
  560.  
  561. &lt;figure class="align-center zoomable"&gt;
  562.            &lt;a href="https://images.theconversation.com/files/628843/original/file-20241030-19-r05b6i.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=1000&amp;amp;fit=clip"&gt;&lt;img alt="An infographic showing the layers of the atmosphere, starting with the troposphere closest to Earth, then the stratosphere, mesosphere, thermosphere and exosphere, farthest from Earth." src="https://images.theconversation.com/files/628843/original/file-20241030-19-r05b6i.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;fit=clip" srcset="https://images.theconversation.com/files/628843/original/file-20241030-19-r05b6i.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=930&amp;amp;fit=crop&amp;amp;dpr=1 600w, https://images.theconversation.com/files/628843/original/file-20241030-19-r05b6i.png?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=930&amp;amp;fit=crop&amp;amp;dpr=2 1200w, https://images.theconversation.com/files/628843/original/file-20241030-19-r05b6i.png?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=930&amp;amp;fit=crop&amp;amp;dpr=3 1800w, https://images.theconversation.com/files/628843/original/file-20241030-19-r05b6i.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=1168&amp;amp;fit=crop&amp;amp;dpr=1 754w, https://images.theconversation.com/files/628843/original/file-20241030-19-r05b6i.png?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=1168&amp;amp;fit=crop&amp;amp;dpr=2 1508w, https://images.theconversation.com/files/628843/original/file-20241030-19-r05b6i.png?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=1168&amp;amp;fit=crop&amp;amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"&gt;&lt;/a&gt;
  563.            &lt;figcaption&gt;
  564.              &lt;span class="caption"&gt;The ISS orbits in the thermosphere, about 200 miles (322 km) from Earth.&lt;/span&gt;
  565.              &lt;span class="attribution"&gt;&lt;a class="source" href="https://www.nesdis.noaa.gov/news/peeling-back-the-layers-of-the-atmosphere"&gt;NOAA&lt;/a&gt;, &lt;a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/"&gt;CC BY-ND&lt;/a&gt;&lt;/span&gt;
  566.            &lt;/figcaption&gt;
  567.          &lt;/figure&gt;
  568.  
  569. &lt;h2&gt;Why doesn’t the ISS burn up?&lt;/h2&gt;
  570.  
  571. &lt;p&gt;So why doesn’t this happen to the International Space Station? &lt;/p&gt;
  572.  
  573. &lt;p&gt;The ISS does not fly in the mesosphere. Instead, the ISS flies in a higher and much less dense layer of the atmosphere &lt;a href="https://spaceplace.nasa.gov/thermosphere/en/"&gt;called the thermosphere&lt;/a&gt;, which extends from 50 miles (80 km) to 440 miles (708 km) above Earth.&lt;/p&gt;
  574.  
  575. &lt;p&gt;&lt;a href="https://www.britannica.com/science/Karman-line"&gt;The Kármán line&lt;/a&gt;, which is considered the boundary of space, is in the thermosphere, 62 miles (100 kilometers) above the surface of the Earth. The space station flies even higher, at about 250 miles (402 km) above the surface. &lt;/p&gt;
  576.  
  577. &lt;p&gt;The thermosphere has too few particles to transmit heat. At the height of the space station, the atmosphere is so thin that to collect enough particles to equal the mass of just one apple, you would need a box the size of Lake Superior!  &lt;/p&gt;
  578.  
  579. &lt;p&gt;As a result, the ISS doesn’t experience the same kind of interactions with atmospheric particles, nor the high pressure and heat that meteoroids traveling closer to Earth do, so it doesn’t burn up.&lt;/p&gt;
  580.  
  581. &lt;h2&gt;A high-flying research hub&lt;/h2&gt;
  582.  
  583. &lt;p&gt;Although the ISS doesn’t burn up, it does experience large temperature swings. As it orbits Earth, it is alternately exposed to direct sunlight and darkness. Temperatures can reach 250 degrees Fahrenheit (121 degrees Celsius) when it’s exposed to the Sun, and then they can drop to as low as -250 degrees F (-156 degrees Celsius) when it’s in the dark – a swing of 500 degrees F (277 degrees C) as it moves through orbit.  &lt;/p&gt;
  584.  
  585. &lt;p&gt;The engineers who designed the station carefully selected materials that can handle these temperature swings. The inside of the space station is kept at comfortable temperatures for the astronauts, the same way people on Earth heat and cool our homes to stay comfortable indoors.&lt;/p&gt;
  586.  
  587. &lt;p&gt;&lt;a href="https://www.nasa.gov/missions/station/20-breakthroughs-from-20-years-of-science-aboard-the-international-space-station/"&gt;Research on the ISS&lt;/a&gt; has led to advancements such as improved &lt;a href="https://www.esa.int/Science_Exploration/Human_and_Robotic_Exploration/International_Space_Station_Benefits_for_Humanity/Advanced_NASA_Technology_Supports_Water_Purification_Efforts_Worldwide"&gt;water filtration technologies&lt;/a&gt;, a better understanding of Earth’s &lt;a href="https://www.nasa.gov/earth-science-at-ames/missions/water-and-energy-cycle/"&gt;water and energy cycles&lt;/a&gt;, &lt;a href="https://www.nasa.gov/exploration-research-and-technology/growing-plants-in-space/"&gt;techniques to grow food in space&lt;/a&gt;, &lt;a href="https://www.nasa.gov/humans-in-space/three-space-station-studies-helping-scientists-understand-the-early-universe/"&gt;insights into black holes&lt;/a&gt;, a better understanding of how &lt;a href="https://theconversation.com/spending-time-in-space-can-harm-the-human-body-but-scientists-are-working-to-mitigate-these-risks-before-sending-people-to-mars-210761"&gt;the human body changes&lt;/a&gt; during &lt;a href="https://theconversation.com/does-a-year-in-space-make-you-older-or-younger-111812"&gt;long-duration space travel&lt;/a&gt;, and new studies on a variety of diseases and treatments. &lt;/p&gt;
  588.  
  589. &lt;p&gt;NASA plans to keep the ISS active until 2030, when all of the astronauts will return to Earth and the ISS will be &lt;a href="https://www.nasa.gov/news-release/nasa-selects-international-space-station-us-deorbit-vehicle/"&gt;deorbited&lt;/a&gt;, or brought down from orbit by a specially designed spacecraft.  &lt;/p&gt;
  590.  
  591. &lt;p&gt;As it comes down through Earth’s atmosphere in the deorbiting process, it will enter the mesosphere, where many parts of it will heat up and disintegrate.&lt;/p&gt;
  592.  
  593. &lt;p&gt;Some spacecraft, such as the crew capsules that bring astronauts to and from the ISS, can survive reentry into the atmosphere using their &lt;a href="https://www.sciencedirect.com/topics/engineering/heat-shield"&gt;heat shield&lt;/a&gt;. That’s a special layer made up of materials that are able to withstand very high temperatures. The ISS wasn’t designed for that, so it doesn’t have a heat shield.&lt;/p&gt;
  594.  
  595. &lt;p&gt;If you’d like to see the space station as it passes over your area, you can &lt;a href="https://spotthestation.nasa.gov/"&gt;check out NASA’s website&lt;/a&gt; to find out when it might be visible near you.&lt;/p&gt;
  596.  
  597. &lt;hr&gt;
  598.  
  599. &lt;p&gt;&lt;em&gt;Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to &lt;a href="mailto:curiouskidsus@theconversation.com"&gt;CuriousKidsUS@theconversation.com&lt;/a&gt;. Please tell us your name, age and the city where you live.&lt;/em&gt;&lt;/p&gt;
  600.  
  601. &lt;p&gt;&lt;em&gt;And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.&lt;/em&gt;&lt;/p&gt;&lt;img src="https://counter.theconversation.com/content/240412/count.gif" alt="The Conversation" width="1" height="1" /&gt;
  602. &lt;p class="fine-print"&gt;&lt;em&gt;&lt;span&gt;Kelly Griendling does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.&lt;/span&gt;&lt;/em&gt;&lt;/p&gt;</content>
  603.    <summary>The International Space Station is an engineering feat that has led to countless scientific discoveries. Like the thousands of satellites in orbit, it manages to stay up in the atmosphere.</summary>
  604.    <author>
  605.      <name>Kelly Griendling, Lecturer of Aerospace Engineering, Georgia Institute of Technology</name>
  606.      <foaf:homepage rdf:resource="https://theconversation.com/profiles/kelly-griendling-2225547"/>
  607.    </author>
  608.    <rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
  609.  </entry>
  610.  <entry>
  611.    <id>tag:theconversation.com,2011:article/245763</id>
  612.    <published>2024-12-16T03:32:04Z</published>
  613.    <updated>2024-12-16T03:32:04Z</updated>
  614.    <link rel="alternate" type="text/html" href="https://theconversation.com/what-is-a-dark-comet-a-quick-guide-to-the-new-kids-in-the-solar-system-245763"/>
  615.    <title>What is a dark comet? A quick guide to the ‘new’ kids in the Solar System</title>
  616.    <content type="html">&lt;figure&gt;&lt;img src="https://images.theconversation.com/files/638686/original/file-20241215-19-i9edo8.jpg?ixlib=rb-4.1.0&amp;amp;rect=9%2C82%2C6133%2C4089&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=496&amp;amp;fit=clip" /&gt;&lt;figcaption&gt;&lt;span class="caption"&gt;Artist&amp;#39;s impression of &amp;#39;Oumuamua.&lt;/span&gt; &lt;span class="attribution"&gt;&lt;a class="source" href="https://www.esa.int/ESA_Multimedia/Images/2018/06/Artist_impression_of_Oumuamua"&gt;ESA/Hubble, NASA, ESO, M. Kornmesser&lt;/a&gt;&lt;/span&gt;&lt;/figcaption&gt;&lt;/figure&gt;&lt;p&gt;In 2017, &lt;a href="https://www.jpl.nasa.gov/news/nasa-learns-more-about-interstellar-visitor-oumuamua/"&gt;NASA discovered&lt;/a&gt; and later confirmed the first interstellar object to enter our Solar System. &lt;/p&gt;
  617.  
  618. &lt;p&gt;It wasn’t aliens. But artist impressions of the object (called ‘Oumuamua, the Hawaiian word for “scout”) do resemble an alien spaceship out of a sci-fi novel. This strange depiction is because astronomers don’t quite know how to classify the interstellar visitor.&lt;/p&gt;
  619.  
  620. &lt;p&gt;Its speed and path around the Sun don’t match a typical asteroid, but it also has no bright tail or nucleus (icy core) we normally associate with comets. However, 'Oumuamua has erratic motions that are consistent with gas escaping from its surface. This “dark comet” has had astronomers scratching their heads ever since.&lt;/p&gt;
  621.  
  622. &lt;figure class="align-center zoomable"&gt;
  623.            &lt;a href="https://images.theconversation.com/files/638085/original/file-20241212-17-1psb8f.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=1000&amp;amp;fit=clip"&gt;&lt;img alt="An elongated rock partially lit by the sun on a dark background." src="https://images.theconversation.com/files/638085/original/file-20241212-17-1psb8f.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;fit=clip" srcset="https://images.theconversation.com/files/638085/original/file-20241212-17-1psb8f.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=338&amp;amp;fit=crop&amp;amp;dpr=1 600w, https://images.theconversation.com/files/638085/original/file-20241212-17-1psb8f.jpg?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=338&amp;amp;fit=crop&amp;amp;dpr=2 1200w, https://images.theconversation.com/files/638085/original/file-20241212-17-1psb8f.jpg?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=338&amp;amp;fit=crop&amp;amp;dpr=3 1800w, https://images.theconversation.com/files/638085/original/file-20241212-17-1psb8f.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=424&amp;amp;fit=crop&amp;amp;dpr=1 754w, https://images.theconversation.com/files/638085/original/file-20241212-17-1psb8f.jpg?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=424&amp;amp;fit=crop&amp;amp;dpr=2 1508w, https://images.theconversation.com/files/638085/original/file-20241212-17-1psb8f.jpg?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=424&amp;amp;fit=crop&amp;amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"&gt;&lt;/a&gt;
  624.            &lt;figcaption&gt;
  625.              &lt;span class="caption"&gt;An artist’s impression of the dark comet ‘Oumuamua.&lt;/span&gt;
  626.              &lt;span class="attribution"&gt;&lt;a class="source" href="https://www.eso.org/public/news/eso1737/"&gt;European Southern Observatory / M. Kornmesser&lt;/a&gt;&lt;/span&gt;
  627.            &lt;/figcaption&gt;
  628.          &lt;/figure&gt;
  629.  
  630. &lt;p&gt;Flash forward to today, and more of these mysterious objects have been discovered, with &lt;a href="https://www.jpl.nasa.gov/news/nasa-researchers-discover-more-dark-comets/"&gt;another ten announced just last week&lt;/a&gt;. While their nature and origins remain elusive, &lt;a href="https://www.darrylseligman.com/home-1/project-one-f5w4d-wbde2"&gt;astronomers recently confirmed&lt;/a&gt; dark comets fall into two main categories: smaller objects that reside in our inner Solar System, and larger objects (100 metres or more) that remain beyond the orbit of Jupiter.&lt;/p&gt;
  631.  
  632. &lt;p&gt;In fact, 3200 Phaethon – the parent body of the famous Geminid meteor shower – may be one of these objects. &lt;/p&gt;
  633.  
  634. &lt;h2&gt;How do dark comets differ from normal comets?&lt;/h2&gt;
  635.  
  636. &lt;p&gt;Comets, often described as the Solar System’s “dirty snowballs”, are icy bodies made of rock, dust and ices. These relics of the early Solar System are critical to unlocking key mysteries around our planet’s formation, the origins of Earth’s water, and even &lt;a href="https://www.esa.int/Science_Exploration/Space_Science/Rosetta/Rosetta_s_comet_contains_ingredients_for_life"&gt;the ingredients for life&lt;/a&gt;.&lt;/p&gt;
  637.  
  638. &lt;p&gt;Astronomers are able to study comets as they make their close approach to our Sun. Their &lt;a href="https://theconversation.com/the-best-comet-of-the-year-is-finally-here-heres-everything-you-need-to-know-239300"&gt;brilliant tails&lt;/a&gt; form as sunlight vaporises their icy surfaces. But not all comets put on such a dazzling display.&lt;/p&gt;
  639.  
  640. &lt;p&gt;The newly discovered dark comets challenge our typical understanding of these celestial wanderers.&lt;/p&gt;
  641.  
  642. &lt;figure class="align-right zoomable"&gt;
  643.            &lt;a href="https://images.theconversation.com/files/638679/original/file-20241215-25-p1axbq.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=1000&amp;amp;fit=clip"&gt;&lt;img alt="" src="https://images.theconversation.com/files/638679/original/file-20241215-25-p1axbq.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=237&amp;amp;fit=clip" srcset="https://images.theconversation.com/files/638679/original/file-20241215-25-p1axbq.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=398&amp;amp;fit=crop&amp;amp;dpr=1 600w, https://images.theconversation.com/files/638679/original/file-20241215-25-p1axbq.jpg?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=398&amp;amp;fit=crop&amp;amp;dpr=2 1200w, https://images.theconversation.com/files/638679/original/file-20241215-25-p1axbq.jpg?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=398&amp;amp;fit=crop&amp;amp;dpr=3 1800w, https://images.theconversation.com/files/638679/original/file-20241215-25-p1axbq.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=500&amp;amp;fit=crop&amp;amp;dpr=1 754w, https://images.theconversation.com/files/638679/original/file-20241215-25-p1axbq.jpg?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=500&amp;amp;fit=crop&amp;amp;dpr=2 1508w, https://images.theconversation.com/files/638679/original/file-20241215-25-p1axbq.jpg?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=500&amp;amp;fit=crop&amp;amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"&gt;&lt;/a&gt;
  644.            &lt;figcaption&gt;
  645.              &lt;span class="caption"&gt;Image of comet C/2023 A3 Tsuchinshan-ATLAS taken by astronauts aboard the International Space Station.&lt;/span&gt;
  646.              &lt;span class="attribution"&gt;&lt;span class="source"&gt;NASA&lt;/span&gt;&lt;/span&gt;
  647.            &lt;/figcaption&gt;
  648.          &lt;/figure&gt;
  649.  
  650. &lt;p&gt;Dark comets are more elusive than their bright siblings. They lack the glowing tails and instead resemble asteroids, appearing as a faint point of light against the vast darkness of space. &lt;/p&gt;
  651.  
  652. &lt;p&gt;However, their orbits set them apart. Like bright comets, dark comets follow elongated, elliptical paths that bring them close to the Sun before sweeping back out to the farthest reaches of the Solar System.&lt;/p&gt;
  653.  
  654. &lt;p&gt;They go beyond Pluto, some even making it out to the Oort Cloud, a vast bubble of tiny objects at the fringe of our Solar System. Their speed and paths are what allow astronomers to determine their origins.&lt;/p&gt;
  655.  
  656. &lt;figure class="align-center zoomable"&gt;
  657.            &lt;a href="https://images.theconversation.com/files/638626/original/file-20241215-15-lwblec.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=1000&amp;amp;fit=clip"&gt;&lt;img alt="Two objects on a starry background: a small rock on the left, and a larger, brighter object on the right." src="https://images.theconversation.com/files/638626/original/file-20241215-15-lwblec.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;fit=clip" srcset="https://images.theconversation.com/files/638626/original/file-20241215-15-lwblec.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=338&amp;amp;fit=crop&amp;amp;dpr=1 600w, https://images.theconversation.com/files/638626/original/file-20241215-15-lwblec.png?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=338&amp;amp;fit=crop&amp;amp;dpr=2 1200w, https://images.theconversation.com/files/638626/original/file-20241215-15-lwblec.png?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=338&amp;amp;fit=crop&amp;amp;dpr=3 1800w, https://images.theconversation.com/files/638626/original/file-20241215-15-lwblec.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=424&amp;amp;fit=crop&amp;amp;dpr=1 754w, https://images.theconversation.com/files/638626/original/file-20241215-15-lwblec.png?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=424&amp;amp;fit=crop&amp;amp;dpr=2 1508w, https://images.theconversation.com/files/638626/original/file-20241215-15-lwblec.png?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=424&amp;amp;fit=crop&amp;amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"&gt;&lt;/a&gt;
  658.            &lt;figcaption&gt;
  659.              &lt;span class="caption"&gt;A comparison of dark comets and bright comets set against the Milky Way. On the left, a small, rocky, dark comet represents their typical size of one metre to a few hundred metres wide. On the right is a larger, icy, bright comet with a glowing tail, whose size ranges from 750 metres to 20 kilometres wide. The stark difference in size explains why dark comets lack the bright, visible tails of their larger, more iconic counterparts.&lt;/span&gt;
  660.              &lt;span class="attribution"&gt;&lt;span class="source"&gt;Composition: Dr Kirsten Banks; Background image: R. Wesson/ESO; Dark comet: Nicole Smith/University of Michigan, made with Midjourney; Bright comet: Linda Davison&lt;/span&gt;&lt;/span&gt;
  661.            &lt;/figcaption&gt;
  662.          &lt;/figure&gt;
  663.  
  664. &lt;p&gt;But what makes these comets so dark? There are three main reasons: size, spin and composition or age.&lt;/p&gt;
  665.  
  666. &lt;p&gt;Dark comets are often small, just a few metres to a few hundred metres wide. This leaves less surface area for material to escape and form into the beautiful tails we see on typical comets. They often spin quite rapidly and disperse escaping gas and dust in all directions, making them less visible.&lt;/p&gt;
  667.  
  668. &lt;p&gt;Lastly, their composition and age may result in weaker or no gas loss, as the materials that go into the tails of bright comets are depleted over time.&lt;/p&gt;
  669.  
  670. &lt;p&gt;These hidden travellers may be just as important for astronomical studies, and they may even be related to their bright counterparts. Now, the challenge is to find more dark comets.&lt;/p&gt;
  671.  
  672. &lt;h2&gt;How can we find dark comets?&lt;/h2&gt;
  673.  
  674. &lt;p&gt;How do we even find these mysterious dark comets in the first place? As they get closer to the Sun, we don’t see spectacular tails of debris.&lt;/p&gt;
  675.  
  676. &lt;p&gt;Instead, we rely on the light they reflect from our Sun.&lt;/p&gt;
  677.  
  678. &lt;figure class="align-center zoomable"&gt;
  679.            &lt;a href="https://images.theconversation.com/files/638084/original/file-20241212-15-he3t7o.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=1000&amp;amp;fit=clip"&gt;&lt;img alt="A series of bright streaks on a black background, with one light source circled in the centre." src="https://images.theconversation.com/files/638084/original/file-20241212-15-he3t7o.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;fit=clip" srcset="https://images.theconversation.com/files/638084/original/file-20241212-15-he3t7o.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=341&amp;amp;fit=crop&amp;amp;dpr=1 600w, https://images.theconversation.com/files/638084/original/file-20241212-15-he3t7o.jpg?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=341&amp;amp;fit=crop&amp;amp;dpr=2 1200w, https://images.theconversation.com/files/638084/original/file-20241212-15-he3t7o.jpg?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=341&amp;amp;fit=crop&amp;amp;dpr=3 1800w, https://images.theconversation.com/files/638084/original/file-20241212-15-he3t7o.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=429&amp;amp;fit=crop&amp;amp;dpr=1 754w, https://images.theconversation.com/files/638084/original/file-20241212-15-he3t7o.jpg?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=429&amp;amp;fit=crop&amp;amp;dpr=2 1508w, https://images.theconversation.com/files/638084/original/file-20241212-15-he3t7o.jpg?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=429&amp;amp;fit=crop&amp;amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"&gt;&lt;/a&gt;
  680.            &lt;figcaption&gt;
  681.              &lt;span class="caption"&gt;Several astronomical images are combined to capture the faint, fast moving object ‘Oumuamua in the centre. The white streaks are stars.&lt;/span&gt;
  682.              &lt;span class="attribution"&gt;&lt;a class="source" href="https://www.eso.org/public/news/eso1737/"&gt;ESO/K. Meech et al.&lt;/a&gt;&lt;/span&gt;
  683.            &lt;/figcaption&gt;
  684.          &lt;/figure&gt;
  685.  
  686. &lt;p&gt;These little guys might be stealthy for our eyes, but they are often no match for our large telescopes around the world. The discovery of ten new dark comets &lt;a href="https://arxiv.org/abs/2412.07603"&gt;revealed last week&lt;/a&gt; was all thanks to one amazing instrument, the Dark Energy Camera (&lt;a href="https://www.darkenergysurvey.org/the-des-project/instrument/"&gt;DECam&lt;/a&gt;) on a large telescope in Chile. &lt;/p&gt;
  687.  
  688. &lt;p&gt;This camera can’t &lt;a href="https://theconversation.com/why-is-the-universe-ripping-itself-apart-a-new-study-of-exploding-stars-shows-dark-energy-may-be-more-complicated-than-we-thought-220423"&gt;“see” dark energy directly&lt;/a&gt;, but it was designed to take massive photos of our universe – for us to see distant stars, galaxies and even hidden Solar System objects.&lt;/p&gt;
  689.  
  690. &lt;p&gt;In their recent study, astronomers pieced together that some of these nightly images contained likely dark comets. &lt;/p&gt;
  691.  
  692. &lt;figure class="align-center zoomable"&gt;
  693.            &lt;a href="https://images.theconversation.com/files/638630/original/file-20241215-15-d31c6x.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=1000&amp;amp;fit=clip"&gt;&lt;img alt="" src="https://images.theconversation.com/files/638630/original/file-20241215-15-d31c6x.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;fit=clip" srcset="https://images.theconversation.com/files/638630/original/file-20241215-15-d31c6x.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=315&amp;amp;fit=crop&amp;amp;dpr=1 600w, https://images.theconversation.com/files/638630/original/file-20241215-15-d31c6x.png?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=315&amp;amp;fit=crop&amp;amp;dpr=2 1200w, https://images.theconversation.com/files/638630/original/file-20241215-15-d31c6x.png?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=315&amp;amp;fit=crop&amp;amp;dpr=3 1800w, https://images.theconversation.com/files/638630/original/file-20241215-15-d31c6x.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=396&amp;amp;fit=crop&amp;amp;dpr=1 754w, https://images.theconversation.com/files/638630/original/file-20241215-15-d31c6x.png?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=396&amp;amp;fit=crop&amp;amp;dpr=2 1508w, https://images.theconversation.com/files/638630/original/file-20241215-15-d31c6x.png?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=396&amp;amp;fit=crop&amp;amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"&gt;&lt;/a&gt;
  694.            &lt;figcaption&gt;
  695.              &lt;span class="caption"&gt;A) The Dark Energy Camera (DECam), mounted on the Victor M. Blanco four-metre telescope at the Cerro Tololo Inter-American Observatory in the Chilean Andes (Credit: Dark Energy Survey). B) Two examples of newly discovered dark comets within the DECam data, from Seligman et al. (2024).&lt;/span&gt;
  696.              
  697.            &lt;/figcaption&gt;
  698.          &lt;/figure&gt;
  699.  
  700. &lt;p&gt;The good news is, we are starting to focus more attention on these objects and on how to find them.&lt;/p&gt;
  701.  
  702. &lt;p&gt;In even better news, in 2025, we’ll have a brand new mega camera in Chile ready to find them. This will be the Vera C. Rubin Observatory, with the &lt;a href="https://noirlab.edu/public/news/noirlab2407/"&gt;largest digital camera&lt;/a&gt; ever built. &lt;/p&gt;
  703.  
  704. &lt;p&gt;It will allow us to take more images of our night sky more quickly, and see objects that are even fainter. It’s likely that in the next ten years we could double or even triple the amount of known dark comets, and start to understand their interesting origin stories. &lt;/p&gt;
  705.  
  706. &lt;p&gt;There could be more 'Oumuamua-like objects out there, just waiting for us to find them.&lt;/p&gt;&lt;img src="https://counter.theconversation.com/content/245763/count.gif" alt="The Conversation" width="1" height="1" /&gt;
  707. &lt;p class="fine-print"&gt;&lt;em&gt;&lt;span&gt;The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.&lt;/span&gt;&lt;/em&gt;&lt;/p&gt;</content>
  708.    <summary>In 2017, astronomers found an object they’d never seen before. Now, it’s part of a growing category of elusive ‘dark comets’ – and we might find more soon.</summary>
  709.    <author>
  710.      <name>Rebecca Allen, Co-Director Space Technology and Industry Institute, Swinburne University of Technology</name>
  711.      <foaf:homepage rdf:resource="https://theconversation.com/profiles/rebecca-allen-163319"/>
  712.    </author>
  713.    <author>
  714.      <name>Kirsten Banks, Lecturer, School of Science, Computing and Engineering Technologies, Swinburne University of Technology</name>
  715.      <foaf:homepage rdf:resource="https://theconversation.com/profiles/kirsten-banks-2278823"/>
  716.    </author>
  717.    <author>
  718.      <name>Sara Webb, Lecturer, Centre for Astrophysics and Supercomputing, Swinburne University of Technology</name>
  719.      <foaf:homepage rdf:resource="https://theconversation.com/profiles/sara-webb-984920"/>
  720.    </author>
  721.    <rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
  722.  </entry>
  723.  <entry>
  724.    <id>tag:theconversation.com,2011:article/245411</id>
  725.    <published>2024-12-12T13:30:09Z</published>
  726.    <updated>2024-12-12T13:30:09Z</updated>
  727.    <link rel="alternate" type="text/html" href="https://theconversation.com/how-to-catch-a-supernova-explosion-before-it-happens-and-what-we-can-learn-from-it-245411"/>
  728.    <title>How to catch a supernova explosion before it happens – and what we can learn from it</title>
  729.    <content type="html">&lt;figure&gt;&lt;img src="https://images.theconversation.com/files/637200/original/file-20241209-25-8fndzh.png?ixlib=rb-4.1.0&amp;amp;rect=1%2C156%2C1057%2C821&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=496&amp;amp;fit=clip" /&gt;&lt;figcaption&gt;&lt;span class="caption"&gt;Composite image of Homunculus Nebula.&lt;/span&gt; &lt;span class="attribution"&gt;&lt;a class="source" href="https://en.wikipedia.org/wiki/Eta_Carinae#/media/File:Cosmic_Fireworks_in_Ultraviolet_Eta_Carinae_Nebula.tif"&gt;ESA/Hubble/wikipedia&lt;/a&gt;, &lt;a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/"&gt;CC BY-SA&lt;/a&gt;&lt;/span&gt;&lt;/figcaption&gt;&lt;/figure&gt;&lt;p&gt;Stars are born, live and die in spectacular ways, with their deaths marked by one of the biggest known explosions in the Universe. Like a campfire needs wood to keep burning, a star relies on nuclear fusion — primarily using hydrogen as fuel — to generate energy and counteract the crushing force of its own gravity.&lt;/p&gt;
  730.  
  731. &lt;p&gt;But when the fuel runs out, the outward pressure vanishes, and the star collapses under its own weight, falling at nearly the speed of light, crashing into the core and rebounding outward. Within seconds, the star is violently blown apart, hurling stellar debris into space at speeds thousands of times faster than the &lt;a href="https://www.spacex.com/vehicles/starship/"&gt;most powerful rocket ever built&lt;/a&gt;. This is a supernova explosion.&lt;/p&gt;
  732.  
  733. &lt;p&gt;Astronomers aim to understand what types of stars produce different kinds of explosions. Do more massive stars result in brighter explosions? What happens if a star is surrounded by dust and gas when it explodes? &lt;/p&gt;
  734.  
  735. &lt;p&gt;While we have simulations modelling a star’s death, they are difficult to validate. Observing a star’s behaviour in real-time before the explosion could help answer these questions — but finding such a star is no easy task.&lt;/p&gt;
  736.  
  737. &lt;p&gt;Scientists already do this with eruptions on Earth. Volcanologists monitor volcanoes, measuring changes in activity to predict an upcoming eruption. For example, in March 1980, &lt;a href="https://pubs.geoscienceworld.org/gsa/geology/article-abstract/32/2/141/103721/Magmatic-precursors-to-the-18-May-1980-eruption-of?redirectedFrom=fulltext"&gt;Mount St. Helens&lt;/a&gt; in the US began to show some precursor events, such as seismic activity, and dozens of steam eruptions ejecting ash and gas into the atmosphere.&lt;/p&gt;
  738.  
  739. &lt;figure class="align-center "&gt;
  740.            &lt;img alt="Plumes of steam, gas, and ash often occurred at Mount St. Helens in the early 1980s." src="https://images.theconversation.com/files/637202/original/file-20241209-15-n6m9qj.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;fit=clip" srcset="https://images.theconversation.com/files/637202/original/file-20241209-15-n6m9qj.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=406&amp;amp;fit=crop&amp;amp;dpr=1 600w, https://images.theconversation.com/files/637202/original/file-20241209-15-n6m9qj.jpg?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=406&amp;amp;fit=crop&amp;amp;dpr=2 1200w, https://images.theconversation.com/files/637202/original/file-20241209-15-n6m9qj.jpg?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=406&amp;amp;fit=crop&amp;amp;dpr=3 1800w, https://images.theconversation.com/files/637202/original/file-20241209-15-n6m9qj.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=510&amp;amp;fit=crop&amp;amp;dpr=1 754w, https://images.theconversation.com/files/637202/original/file-20241209-15-n6m9qj.jpg?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=510&amp;amp;fit=crop&amp;amp;dpr=2 1508w, https://images.theconversation.com/files/637202/original/file-20241209-15-n6m9qj.jpg?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=510&amp;amp;fit=crop&amp;amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"&gt;
  741.            &lt;figcaption&gt;
  742.              &lt;span class="caption"&gt;Plumes of steam, gas, and ash often occurred at Mount St. Helens in the early 1980s.&lt;/span&gt;
  743.              &lt;span class="attribution"&gt;&lt;span class="source"&gt;wikipedia&lt;/span&gt;&lt;/span&gt;
  744.            &lt;/figcaption&gt;
  745.          &lt;/figure&gt;
  746.  
  747. &lt;p&gt;Two months later, an earthquake triggered the largest landslide ever recorded, releasing built up pressure in the magma chamber, resulting in a catastrophic eruption that devastated an area of almost 232 square miles (600 square kilometres).&lt;/p&gt;
  748.  
  749. &lt;h2&gt;Pre-supernova eruptions&lt;/h2&gt;
  750.  
  751. &lt;p&gt;Massive stars – larger than around 10 times the mass of the Sun – can do the same thing, albeit at much larger scales. In 2009, astronomers observed a bright event 65 million light years away that on first impressions resembled a supernova explosion.&lt;/p&gt;
  752.  
  753. &lt;p&gt;Dubbed &lt;a href="https://iopscience.iop.org/article/10.1088/0004-637X/767/1/1"&gt;SN 2009ip&lt;/a&gt;, the explosion did not brighten as expected and was reclassified shortly after discovery as a “supernova impostor” – a giant eruption which ultimately does not destroy the star.&lt;/p&gt;
  754.  
  755. &lt;p&gt;Over the next three years, the star underwent many rapid “flickering” events, a bit like quickly turning on and off a light bulb. Finally, in 2012, &lt;a href="https://astrobites.org/2013/03/18/sn2009ip-dead-or-just-resting/"&gt;an unexpected supernova&lt;/a&gt; occurred. The evolution of the supernova explosion is still being studied to this day, and what exactly happened from 2009 to 2012 remains a mystery.&lt;/p&gt;
  756.  
  757. &lt;p&gt;In a recent paper, &lt;a href="https://www.aanda.org/articles/aa/full_html/2024/04/aa49350-24/aa49350-24.html"&gt;published in Astronomy and Astrophysics&lt;/a&gt;, our team found a peculiar star in the Virgo Cluster, coincidentally also 65 million light years away. Unlike SN 2009ip, the star lacked hydrogen and was composed primarily of helium. The star was observed very slowly increasing its brightness for over five years – akin to slowly turning on a bulb using a dimmer switch – before a supernova was observed.&lt;/p&gt;
  758.  
  759. &lt;p&gt;The supernova, labelled as &lt;a href="https://www.aanda.org/articles/aa/full_html/2024/04/aa49350-24/aa49350-24.html"&gt;SN 2023fyq&lt;/a&gt;, provided astronomers with a rare opportunity to capture the first light from the supernova explosion, known as shock breakout, from observatories worldwide and in space, largely due to the daily monitoring of the precursor activity.&lt;/p&gt;
  760.  
  761. &lt;h2&gt;Clash with current theory&lt;/h2&gt;
  762.  
  763. &lt;p&gt;This precursor activity offers an exciting chance to uncover the mysteries of supernova explosions, shedding light on both the conditions leading up to and following these cosmic events.&lt;/p&gt;
  764.  
  765. &lt;p&gt;The underlying cause of this pre-supernova activity remains unclear. It is thought that an isolated massive star does not experience such rapid fluctuations in brightness. In the final moments of a star’s life, its core undergoes rapid evolution, desperately attempting to counteract the crushing force of gravity with its dwindling fuel reserves. &lt;/p&gt;
  766.  
  767. &lt;p&gt;However, the star is so large at this stage that any activity in the core doesn’t have enough time to reach the surface. Observing these dramatic changes, occurring so close to the star’s demise, present a significant challenge to current theories.&lt;/p&gt;
  768.  
  769. &lt;p&gt;One compelling hypothesis points to the &lt;a href="https://arxiv.org/abs/2405.04583"&gt;interaction of multiple stars&lt;/a&gt;. Stars are born in dense clouds of gas and dust where multiple stars can form in close proximity. Neighbouring stars may interact gravitationally with one another – exchanging material as they orbit each other.&lt;/p&gt;
  770.  
  771. &lt;p&gt;This mass transfer could account for the changes in brightness observed in SN 2009ip before its explosion and the hydrogen deficiency seen in SN 2023fyq. The companion involved might be another massive star – or perhaps a more exotic object, such as a &lt;a href="https://iopscience.iop.org/article/10.3847/1538-4357/ad3637"&gt;black hole&lt;/a&gt;.&lt;/p&gt;
  772.  
  773. &lt;p&gt;We know not all eruptions will not end in a supernova explosion. For example, in the 1840s, &lt;a href="https://viewspace.org/interactives/unveiling_invisible_universe/variable_stars/eta_carinae"&gt;Eta Carinae&lt;/a&gt; – a star 100 times larger than the Sun – experienced the &lt;a href="https://www.universetoday.com/163535/what-caused-eta-carinaes-1840-great-eruption/"&gt;“Great Eruption”&lt;/a&gt;  launching 30 times the Sun’s mass into space. Although this was an extremely energetic explosion, the massive star was not destroyed. &lt;/p&gt;
  774.  
  775. &lt;p&gt;Do all stars announce their departure? We aren’t sure. &lt;a href="https://iopscience.iop.org/article/10.3847/1538-4357/ac3f3a"&gt;Seemingly normal supernovas&lt;/a&gt; have been observed with precursor eruptions, thanks in part to deep observations catching the faint precursor activity. &lt;/p&gt;
  776.  
  777. &lt;p&gt;In 2025, the &lt;a href="https://www.lsst.org/"&gt;Vera C. Rubin Observatory&lt;/a&gt;, equipped with the &lt;a href="https://www.lsst.org/about/camera"&gt;world’s largest camera&lt;/a&gt;, will begin to study these events. At 3,200-megapixels, it is over 40 times more sensitive than cameras we have available on Earth, providing the opportunity to search for fainter precursor activity.&lt;/p&gt;
  778.  
  779. &lt;p&gt;At Stockholm University, our team is currently using telescopes from the &lt;a href="https://www.eso.org/public/"&gt;European Southern Observatory&lt;/a&gt; and the &lt;a href="https://www.ztf.caltech.edu/"&gt;Zwicky Transient Facility&lt;/a&gt;, including the Nordic Optical Telescope in La Palma, Spain and the Very Large Telescope at Cerro Paranal in the Atacama Desert of northern Chile, to identify the signs that indicate a star is nearing the end of its life. &lt;/p&gt;
  780.  
  781. &lt;p&gt;By recognising these signals, we can alert the scientific community and be ready to watch as a star experiences its final, dramatic moments.&lt;/p&gt;&lt;img src="https://counter.theconversation.com/content/245411/count.gif" alt="The Conversation" width="1" height="1" /&gt;
  782. &lt;p class="fine-print"&gt;&lt;em&gt;&lt;span&gt;Seán Brennan does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.&lt;/span&gt;&lt;/em&gt;&lt;/p&gt;</content>
  783.    <summary>Just like volcanologists monitor volcano activity to predict eruptions, astronomers can monitor stars to predict explosions.</summary>
  784.    <author>
  785.      <name>Seán Brennan, Postdoctoral Reseracher in the Supernova and Explosive Transient Group, Stockholm University</name>
  786.      <foaf:homepage rdf:resource="https://theconversation.com/profiles/sean-brennan-2274440"/>
  787.    </author>
  788.    <rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
  789.  </entry>
  790.  <entry>
  791.    <id>tag:theconversation.com,2011:article/245413</id>
  792.    <published>2024-12-11T12:58:39Z</published>
  793.    <updated>2024-12-11T12:58:39Z</updated>
  794.    <link rel="alternate" type="text/html" href="https://theconversation.com/weve-found-an-answer-to-the-puzzle-of-how-the-largest-galaxies-formed-245413"/>
  795.    <title>We’ve found an answer to the puzzle of how the largest galaxies formed</title>
  796.    <content type="html">&lt;figure&gt;&lt;img src="https://images.theconversation.com/files/637126/original/file-20241209-17-ixdued.jpg?ixlib=rb-4.1.0&amp;amp;rect=14%2C12%2C1209%2C746&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=496&amp;amp;fit=clip" /&gt;&lt;figcaption&gt;&lt;span class="caption"&gt;Two galaxies — also known as NGC 4038 and NGC 4039 — colliding to eventually form an elliptical galaxy.&lt;/span&gt; &lt;span class="attribution"&gt;&lt;span class="source"&gt;Nasa&lt;/span&gt;&lt;/span&gt;&lt;/figcaption&gt;&lt;/figure&gt;&lt;p&gt;It is as humbling as it is motivating to think about how much we still have to learn about the universe. My collaborators and I have just tackled one of astrophysics’ enduring mysteries: how massive elliptical galaxies can form.&lt;/p&gt;
  797.  
  798. &lt;p&gt;Now, for the first time, we have solid observational evidence that provides an answer. Our results &lt;a href="https://www.nature.com/articles/s41586-024-08201-6"&gt;have recently been published in Nature&lt;/a&gt;.&lt;/p&gt;
  799.  
  800. &lt;p&gt;Galaxies in the present-day universe fall into &lt;a href="https://science.nasa.gov/universe/galaxies/types/"&gt;two broad categories&lt;/a&gt;. There are spiral galaxies, like our Milky Way, which are rich in gas and continuously form stars in a rotating disc. There are also elliptical galaxies, which are large and spherical rather than flat, similar to a rugby ball. The latter don’t produce new stars but are dominated by stars formed more than 10 billion years ago. &lt;/p&gt;
  801.  
  802. &lt;p&gt;The formation of elliptical galaxies has long been difficult to explain with cosmological models describing the evolution of the universe from the Big Bang to now. One of the challenges is that star formation during the era when elliptical galaxies formed (10 billion to 12 billion years ago) was &lt;a href="https://academic.oup.com/mnras/article/511/1/1502/6516430"&gt;thought to occur within large rotating discs&lt;/a&gt;, similar to our own Milky Way. &lt;/p&gt;
  803.  
  804. &lt;p&gt;So how did the galaxies transform their shape from flat discs to three-dimensional elliptical galaxies? &lt;/p&gt;
  805.  
  806. &lt;h2&gt;Observations with Alma&lt;/h2&gt;
  807.  
  808. &lt;p&gt;By analysing data from the &lt;a href="https://www.eso.org/public/unitedkingdom/teles-instr/alma/"&gt;Atacama Large Millimeter/submillimeter Array (Alma)&lt;/a&gt;, we identified the birth sites of giant elliptical galaxies. We discovered that local elliptical galaxies can form through intense and short-lived star formation episodes early in the universe, as opposed to starting out as a rotating disc and becoming more elliptical over time.&lt;/p&gt;
  809.  
  810. &lt;figure class="align-center zoomable"&gt;
  811.            &lt;a href="https://images.theconversation.com/files/637146/original/file-20241209-17-9pcefu.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=1000&amp;amp;fit=clip"&gt;&lt;img alt="Three Alma antennas on the 5000-metre altitude plateau of Chajnantor in Chile." src="https://images.theconversation.com/files/637146/original/file-20241209-17-9pcefu.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;fit=clip" srcset="https://images.theconversation.com/files/637146/original/file-20241209-17-9pcefu.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=399&amp;amp;fit=crop&amp;amp;dpr=1 600w, https://images.theconversation.com/files/637146/original/file-20241209-17-9pcefu.jpg?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=399&amp;amp;fit=crop&amp;amp;dpr=2 1200w, https://images.theconversation.com/files/637146/original/file-20241209-17-9pcefu.jpg?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=399&amp;amp;fit=crop&amp;amp;dpr=3 1800w, https://images.theconversation.com/files/637146/original/file-20241209-17-9pcefu.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=501&amp;amp;fit=crop&amp;amp;dpr=1 754w, https://images.theconversation.com/files/637146/original/file-20241209-17-9pcefu.jpg?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=501&amp;amp;fit=crop&amp;amp;dpr=2 1508w, https://images.theconversation.com/files/637146/original/file-20241209-17-9pcefu.jpg?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=501&amp;amp;fit=crop&amp;amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"&gt;&lt;/a&gt;
  812.            &lt;figcaption&gt;
  813.              &lt;span class="caption"&gt;Three Alma antennas on the 5km altitude plateau of Chajnantor in Chile.&lt;/span&gt;
  814.              &lt;span class="attribution"&gt;&lt;span class="source"&gt;wikipedia&lt;/span&gt;, &lt;a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/"&gt;CC BY-SA&lt;/a&gt;&lt;/span&gt;
  815.            &lt;/figcaption&gt;
  816.          &lt;/figure&gt;
  817.  
  818. &lt;p&gt;Our study examined the distribution of dust in more than 100 distant galaxies, which we know were forming lots of stars back when the universe was between 2.2 billion and 5.9 billion years old. Dust indicates the presence of gas — the material from which new stars are formed — and enables us to study the regions within a galaxy that are actively forming new stars.&lt;/p&gt;
  819.  
  820. &lt;p&gt;Using a novel observational technique, we found that the dust in these distant galaxies is extremely compact and isn’t what we expected from flat disc-shaped galaxies. Furthermore, we were able to infer the three-dimensional geometry of the dust-emitting regions. This analysis indicates that most of the early star-forming galaxies were actually spherical rather than disc-shaped. In fact, they closely resemble the shape of elliptical galaxies near us today.&lt;/p&gt;
  821.  
  822. &lt;p&gt;We then used cosmological computer simulations to interpret the observational results and understand the physical mechanisms that may have caused dust and gas to sink into the centres of these distant, star-forming galaxies. &lt;/p&gt;
  823.  
  824. &lt;p&gt;Our analysis reveals that the simultaneous action of cold gas streams from surrounding galaxies along with galaxy interactions and mergers can drive gas and dust into compact, star-forming cores within these galaxies. The simulations also show us that this process was common in the early universe, providing a key explanation for the rapid formation of elliptical galaxies.&lt;/p&gt;
  825.  
  826. &lt;p&gt;Our findings add a crucial piece to this puzzle, advancing our understanding of galaxy formation and evolution.&lt;/p&gt;
  827.  
  828. &lt;h2&gt;A novel observational technique&lt;/h2&gt;
  829.  
  830. &lt;p&gt;This discovery was made possible by a novel technique for analysing ALMA observations. Alma data are different than the images we are used to see from optical telescopes. In fact, Alma operates by combining signals from multiple antennas that work together as a single, giant telescope.&lt;/p&gt;
  831.  
  832. &lt;p&gt;This technique is known as interferometry, and while it allows to obtain sharp images of distant galaxies, the data analysis is more complex than for traditional optical images. Our new technique enables more precise measurements of dust distribution compared to previous methods, offering a significant advancement in this field.&lt;/p&gt;
  833.  
  834. &lt;p&gt;For this research we used archival, &lt;a href="https://sites.google.com/view/a3cosmos"&gt;open-access Alma data&lt;/a&gt; accumulated over several years. This highlights the power of open-source data, where scientists share their findings, and worldwide collaborations in driving scientific breakthroughs.&lt;/p&gt;
  835.  
  836. &lt;p&gt;Future observations with &lt;a href="https://theconversation.com/james-webb-telescope-a-scientist-explains-what-its-first-amazing-images-show-and-how-it-will-change-astronomy-186668"&gt;JWST&lt;/a&gt; and &lt;a href="https://www.esa.int/Science_Exploration/Space_Science/Euclid"&gt;Euclid&lt;/a&gt; space telescopes will further map the distribution of stars in the distant ancestors of today’s elliptical galaxies. And the &lt;a href="https://elt.eso.org/"&gt;Extremely Large Telescope&lt;/a&gt;, with its 39-metre wide mirror, will provide unprecedented detail of the star-forming cores in distant galaxies. &lt;/p&gt;
  837.  
  838. &lt;p&gt;Additionally, sharper observations of gas dynamics with ALma and the &lt;a href="https://www.eso.org/public/unitedkingdom/teles-instr/paranal-observatory/vlt/"&gt;Very Large Telescope&lt;/a&gt; will reveal how gas moves towards galaxy centres, fuelling star formation and shaping the galaxies we see today.&lt;/p&gt;&lt;img src="https://counter.theconversation.com/content/245413/count.gif" alt="The Conversation" width="1" height="1" /&gt;
  839. &lt;p class="fine-print"&gt;&lt;em&gt;&lt;span&gt;Annagrazia Puglisi does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.&lt;/span&gt;&lt;/em&gt;&lt;/p&gt;</content>
  840.    <summary>Elliptical galaxies have long provided a headache for astronomers.</summary>
  841.    <author>
  842.      <name>Annagrazia Puglisi, Anniversary Fellow of Astrophysics, University of Southampton</name>
  843.      <foaf:homepage rdf:resource="https://theconversation.com/profiles/annagrazia-puglisi-1195766"/>
  844.    </author>
  845.    <rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
  846.  </entry>
  847.  <entry>
  848.    <id>tag:theconversation.com,2011:article/239702</id>
  849.    <published>2024-12-09T13:39:46Z</published>
  850.    <updated>2024-12-09T13:39:46Z</updated>
  851.    <link rel="alternate" type="text/html" href="https://theconversation.com/what-is-the-universe-expanding-into-if-its-already-infinite-239702"/>
  852.    <title>What is the universe expanding into if it’s already infinite?</title>
  853.    <content type="html">&lt;figure&gt;&lt;img src="https://images.theconversation.com/files/630980/original/file-20241108-22-fkz1c6.jpg?ixlib=rb-4.1.0&amp;amp;rect=0%2C8%2C5391%2C3581&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=496&amp;amp;fit=clip" /&gt;&lt;figcaption&gt;&lt;span class="caption"&gt;The universe is full of stars, galaxies and planets − it&amp;#39;s expanding every day. &lt;/span&gt; &lt;span class="attribution"&gt;&lt;a class="source" href="https://newsroom.ap.org/detail/PhotoGalleryFarewellSpaceTelescope/a02b0815b0124a3ab43d2516da454974/photo?Query=milky%20way%20galaxy&amp;amp;mediaType=photo&amp;amp;sortBy=&amp;amp;dateRange=Anytime&amp;amp;totalCount=42&amp;amp;currentItemNo=4"&gt;NASA/JPL-Caltech/University of Wisconsin via AP&lt;/a&gt;&lt;/span&gt;&lt;/figcaption&gt;&lt;/figure&gt;
  854.  
  855. &lt;p&gt;&lt;em&gt;&lt;a href="https://theconversation.com/us/topics/curious-kids-us-74795"&gt;Curious Kids&lt;/a&gt; is a series for children of all ages. If you have a question you’d like an expert to answer, send it to &lt;a href="mailto:curiouskidsus@theconversation.com"&gt;curiouskidsus@theconversation.com&lt;/a&gt;.&lt;/em&gt;&lt;/p&gt;
  856.  
  857. &lt;hr&gt;
  858.  
  859. &lt;blockquote&gt;
  860. &lt;p&gt;&lt;strong&gt;What is the universe expanding into if it’s already infinite? – Mael, age 10, Missoula, Montana&lt;/strong&gt;&lt;/p&gt;
  861. &lt;/blockquote&gt;
  862.  
  863. &lt;hr&gt;
  864.  
  865. &lt;p&gt;When you bake a loaf of bread or a batch of muffins, you put the dough into a pan. As the dough bakes in the oven, it expands into the baking pan. Any chocolate chips or blueberries in the muffin batter become farther away from each other as the muffin batter expands. &lt;/p&gt;
  866.  
  867. &lt;p&gt;The expansion of the universe is, in some ways, similar. But this analogy gets one thing wrong – while the dough expands into the baking pan, the universe doesn’t have anything to expand into. It just expands into itself.&lt;/p&gt;
  868.  
  869.  
  870.  
  871. &lt;p&gt;It can feel like a brain teaser, but the universe is considered everything within the universe. In the expanding universe, there is no pan. Just dough. Even if there were a pan, it would be part of the universe and therefore it would expand with the pan. &lt;/p&gt;
  872.  
  873. &lt;p&gt;Even for me, a &lt;a href="https://www.qu.edu/faculty-and-staff/nicole-granucci/"&gt;teaching professor in physics and astronomy&lt;/a&gt; who has studied the universe for years, these ideas are hard to grasp. You don’t experience anything like this in your daily life. It’s like asking what direction is farther north of the North Pole.&lt;/p&gt;
  874.  
  875. &lt;p&gt;Another way to think about the universe’s expansion is by thinking about how other galaxies are moving away from our galaxy, the Milky Way. Scientists know the universe is expanding because they can track other galaxies as they move away from ours. They define expansion using the rate that other galaxies move away from us. This definition allows them to imagine expansion without needing something to expand into.&lt;/p&gt;
  876.  
  877. &lt;h2&gt;The expanding universe&lt;/h2&gt;
  878.  
  879. &lt;p&gt;The universe started with the Big Bang &lt;a href="https://science.nasa.gov/universe/overview/"&gt;13.8 billion years ago&lt;/a&gt;. The Big Bang describes the origin of the universe as an extremely dense, hot singularity. This tiny point suddenly went through a rapid expansion called inflation, where every place in the universe expanded outward. But the name Big Bang is misleading. &lt;a href="https://theconversation.com/how-could-an-explosive-big-bang-be-the-birth-of-our-universe-128430"&gt;It wasn’t a giant explosion&lt;/a&gt;, as the name suggests, but a time where the universe expanded rapidly. &lt;/p&gt;
  880.  
  881. &lt;p&gt;The universe then quickly condensed and cooled down, and it started making matter and light. Eventually, it evolved to what we know today as our universe.&lt;/p&gt;
  882.  
  883. &lt;p&gt;The idea that our universe was not static and could be expanding or contracting was &lt;a href="https://doi.org/10.1119/1.2830536"&gt;first published by the physicist Alexander Friedman&lt;/a&gt; in 1922. He confirmed mathematically that the universe is expanding.&lt;/p&gt;
  884.  
  885. &lt;p&gt;While Friedman proved that the universe was expanding, at least in some spots, it was Edwin Hubble who looked deeper into the expansion rate. Many other scientists confirmed that other galaxies are moving away from the Milky Way, but in 1929, Hubble &lt;a href="https://doi.org/10.1073/pnas.15.3.168"&gt;published his famous paper&lt;/a&gt; that confirmed the entire universe was expanding, and that the rate it’s expanding at is increasing.&lt;/p&gt;
  886.  
  887. &lt;p&gt;This discovery continues to puzzle astrophysicists. What phenomenon allows the universe to overcome the force of gravity keeping it together while also expanding by pulling objects in the universe apart? And on top of all that, its expansion rate is speeding up over time.&lt;/p&gt;
  888.  
  889. &lt;p&gt;Many scientists use a visual called the expansion funnel to describe how the universe’s expansion has sped up since the Big Bang. Imagine a deep funnel with a wide brim. The left side of the funnel – the narrow end – represents the beginning of the universe. As you move toward the right, you are moving forward in time. The cone widening represents the universe’s expansion. &lt;/p&gt;
  890.  
  891. &lt;figure class="align-center zoomable"&gt;
  892.            &lt;a href="https://images.theconversation.com/files/626522/original/file-20241017-15-daaqry.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=1000&amp;amp;fit=clip"&gt;&lt;img alt="A funnel on its side, with a bright spot at the left which fans out into a wide mouth on the right." src="https://images.theconversation.com/files/626522/original/file-20241017-15-daaqry.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;fit=clip" srcset="https://images.theconversation.com/files/626522/original/file-20241017-15-daaqry.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=346&amp;amp;fit=crop&amp;amp;dpr=1 600w, https://images.theconversation.com/files/626522/original/file-20241017-15-daaqry.png?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=346&amp;amp;fit=crop&amp;amp;dpr=2 1200w, https://images.theconversation.com/files/626522/original/file-20241017-15-daaqry.png?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=346&amp;amp;fit=crop&amp;amp;dpr=3 1800w, https://images.theconversation.com/files/626522/original/file-20241017-15-daaqry.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=435&amp;amp;fit=crop&amp;amp;dpr=1 754w, https://images.theconversation.com/files/626522/original/file-20241017-15-daaqry.png?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=435&amp;amp;fit=crop&amp;amp;dpr=2 1508w, https://images.theconversation.com/files/626522/original/file-20241017-15-daaqry.png?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=435&amp;amp;fit=crop&amp;amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"&gt;&lt;/a&gt;
  893.            &lt;figcaption&gt;
  894.              &lt;span class="caption"&gt;The expansion funnel visually shows how the universe’s rate of expansion has increased over time. At the left of the funnel is the Big Bang, and since then, the universe has expanded at a faster and faster rate.&lt;/span&gt;
  895.              &lt;span class="attribution"&gt;&lt;a class="source" href="https://svs.gsfc.nasa.gov/12314/"&gt;NASA&lt;/a&gt;&lt;/span&gt;
  896.            &lt;/figcaption&gt;
  897.          &lt;/figure&gt;
  898.  
  899. &lt;p&gt;Scientists haven’t been able to directly measure where the &lt;a href="https://theconversation.com/explainer-the-mysterious-dark-energy-that-speeds-the-universes-rate-of-expansion-40224"&gt;energy causing this accelerating expansion&lt;/a&gt; comes from. They haven’t been able to detect it or measure it. Because they can’t see or directly measure this type of energy, they call it &lt;a href="https://www.space.com/dark-energy-what-is-it"&gt;dark energy&lt;/a&gt;. &lt;/p&gt;
  900.  
  901. &lt;p&gt;According to researchers’ models, dark energy must be the most common form of energy in the universe, making up about &lt;a href="https://arstechnica.com/science/2013/03/first-planck-results-the-universe-is-still-weird-and-interesting/"&gt;68% of the total energy in the universe&lt;/a&gt;. The energy from everyday matter, which makes up the Earth, the Sun and everything we can see, accounts for only about 5% of all energy.&lt;/p&gt;
  902.  
  903. &lt;figure class="align-center zoomable"&gt;
  904.            &lt;a href="https://images.theconversation.com/files/631525/original/file-20241112-15-xbddu4.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=1000&amp;amp;fit=clip"&gt;&lt;img alt="A pie chart showing 68% of the universe as dark energy, 27% as dark matter and 5% as ordinary matter." src="https://images.theconversation.com/files/631525/original/file-20241112-15-xbddu4.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;fit=clip" srcset="https://images.theconversation.com/files/631525/original/file-20241112-15-xbddu4.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=600&amp;amp;fit=crop&amp;amp;dpr=1 600w, https://images.theconversation.com/files/631525/original/file-20241112-15-xbddu4.png?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=600&amp;amp;fit=crop&amp;amp;dpr=2 1200w, https://images.theconversation.com/files/631525/original/file-20241112-15-xbddu4.png?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=600&amp;amp;fit=crop&amp;amp;dpr=3 1800w, https://images.theconversation.com/files/631525/original/file-20241112-15-xbddu4.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=754&amp;amp;fit=crop&amp;amp;dpr=1 754w, https://images.theconversation.com/files/631525/original/file-20241112-15-xbddu4.png?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=754&amp;amp;fit=crop&amp;amp;dpr=2 1508w, https://images.theconversation.com/files/631525/original/file-20241112-15-xbddu4.png?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=754&amp;amp;fit=crop&amp;amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"&gt;&lt;/a&gt;
  905.            &lt;figcaption&gt;
  906.              &lt;span class="caption"&gt;Dark matter and dark energy make up most of the universe.&lt;/span&gt;
  907.              &lt;span class="attribution"&gt;&lt;a class="source" href="https://www.flickr.com/photos/greenbankobservatory/38462171061"&gt;Green Bank Observatory&lt;/a&gt;, &lt;a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/"&gt;CC BY-NC-ND&lt;/a&gt;&lt;/span&gt;
  908.            &lt;/figcaption&gt;
  909.          &lt;/figure&gt;
  910.  
  911. &lt;h2&gt;Outside the expansion funnel&lt;/h2&gt;
  912.  
  913. &lt;p&gt;So, what is outside the expansion funnel? &lt;/p&gt;
  914.  
  915. &lt;p&gt;Scientists don’t have evidence of anything beyond our known universe. However, some predict that &lt;a href="https://theconversation.com/the-multiverse-is-huge-in-pop-culture-right-now-but-what-is-it-and-does-it-really-exist-181781"&gt;there could be multiple universes&lt;/a&gt;. A model that includes multiple universes could fix some of the problems scientists encounter with the current models of our universe.&lt;/p&gt;
  916.  
  917. &lt;p&gt;One major problem with our current physics is that &lt;a href="https://bigthink.com/starts-with-a-bang/problem-gravity-quantum-physics/"&gt;researchers can’t integrate&lt;/a&gt; &lt;a href="https://www.energy.gov/science/doe-explainsquantum-mechanics"&gt;quantum mechanics&lt;/a&gt;, which describes how physics works on a very small scale, and gravity, which &lt;a href="https://www.britannica.com/science/gravity-physics"&gt;governs large-scale physics&lt;/a&gt;.&lt;/p&gt;
  918.  
  919. &lt;p&gt;The rules for how matter behaves at the small scale depend on probability and quantized, or fixed, amounts of energy. At this scale, objects can come into and pop out of existence. &lt;a href="https://www.space.com/wave-or-particle-ask-a-spaceman.html"&gt;Matter can behave as a wave&lt;/a&gt;. The quantum world is very different from how we see the world. &lt;/p&gt;
  920.  
  921. &lt;p&gt;At large scales, which physicists call &lt;a href="https://www.livescience.com/47814-classical-mechanics.html"&gt;classical mechanics&lt;/a&gt;, objects behave how we expect them to behave on a day-to-day basis. Objects are not quantized and can have continuous amounts of energy. Objects do not pop in and out of existence. &lt;/p&gt;
  922.  
  923. &lt;p&gt;The quantum world behaves kind of like a light switch, where energy has only an on-off option. The world we see and interact with behaves like a dimmer switch, allowing for all levels of energy.&lt;/p&gt;
  924.  
  925. &lt;p&gt;But researchers run into problems when they try to study gravity at the quantum level. At the small scale, physicists would have to assume gravity is quantized. But &lt;a href="https://www.quantamagazine.org/the-physicist-who-bets-that-gravity-cant-be-quantized-20230710/"&gt;the research many of them have conducted&lt;/a&gt; doesn’t support that idea.&lt;/p&gt;
  926.  
  927. &lt;figure class="align-center zoomable"&gt;
  928.            &lt;a href="https://images.theconversation.com/files/630982/original/file-20241108-19-qmucyz.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=1000&amp;amp;fit=clip"&gt;&lt;img alt="Clouds of gas and stars." src="https://images.theconversation.com/files/630982/original/file-20241108-19-qmucyz.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;fit=clip" srcset="https://images.theconversation.com/files/630982/original/file-20241108-19-qmucyz.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=92&amp;amp;fit=crop&amp;amp;dpr=1 600w, https://images.theconversation.com/files/630982/original/file-20241108-19-qmucyz.jpg?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=92&amp;amp;fit=crop&amp;amp;dpr=2 1200w, https://images.theconversation.com/files/630982/original/file-20241108-19-qmucyz.jpg?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=92&amp;amp;fit=crop&amp;amp;dpr=3 1800w, https://images.theconversation.com/files/630982/original/file-20241108-19-qmucyz.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=115&amp;amp;fit=crop&amp;amp;dpr=1 754w, https://images.theconversation.com/files/630982/original/file-20241108-19-qmucyz.jpg?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=115&amp;amp;fit=crop&amp;amp;dpr=2 1508w, https://images.theconversation.com/files/630982/original/file-20241108-19-qmucyz.jpg?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=115&amp;amp;fit=crop&amp;amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"&gt;&lt;/a&gt;
  929.            &lt;figcaption&gt;
  930.              &lt;span class="caption"&gt;An infinitely expanding universe lies beyond the Milky Way galaxy.&lt;/span&gt;
  931.              &lt;span class="attribution"&gt;&lt;a class="source" href="https://newsroom.ap.org/detail/GalacticSurvey/9112f60b2dc84c849daffb17f6015f18/photo?Query=milky%20way%20galaxy&amp;amp;mediaType=photo&amp;amp;sortBy=&amp;amp;dateRange=Anytime&amp;amp;totalCount=42&amp;amp;currentItemNo=3"&gt;DECaPS2/DOE/FNAL/DECam/CTIO/NOIRLab/NSF/AURA, M. Zamani &amp;amp; D. de Martin via AP&lt;/a&gt;&lt;/span&gt;
  932.            &lt;/figcaption&gt;
  933.          &lt;/figure&gt;
  934.  
  935. &lt;p&gt;One way to make these theories work together is the &lt;a href="https://www.livescience.com/multiverse"&gt;multiverse theory&lt;/a&gt;. There are many theories that look beyond our current universe to explain how gravity and the quantum world work together. Some of the leading theories include &lt;a href="https://www.space.com/17594-string-theory.html"&gt;string theory&lt;/a&gt;, &lt;a href="https://en.wikipedia.org/wiki/Brane_cosmology"&gt;brane cosmology&lt;/a&gt;, &lt;a href="https://www.space.com/loop-quantum-gravity-space-time-quantized"&gt;loop quantum theory&lt;/a&gt; and many others. &lt;/p&gt;
  936.  
  937. &lt;p&gt;Regardless, the universe will continue to expand, with the distance between the Milky Way and most other galaxies getting longer over time. &lt;/p&gt;
  938.  
  939. &lt;hr&gt;
  940.  
  941. &lt;p&gt;&lt;em&gt;Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to &lt;a href="mailto:curiouskidsus@theconversation.com"&gt;CuriousKidsUS@theconversation.com&lt;/a&gt;. Please tell us your name, age and the city where you live.&lt;/em&gt;&lt;/p&gt;
  942.  
  943. &lt;p&gt;&lt;em&gt;And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.&lt;/em&gt;&lt;/p&gt;&lt;img src="https://counter.theconversation.com/content/239702/count.gif" alt="The Conversation" width="1" height="1" /&gt;
  944. &lt;p class="fine-print"&gt;&lt;em&gt;&lt;span&gt;Nicole Granucci does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.&lt;/span&gt;&lt;/em&gt;&lt;/p&gt;</content>
  945.    <summary>The universe is constantly expanding, but how do scientists think about what it’s expanding into?</summary>
  946.    <author>
  947.      <name>Nicole Granucci, Instructor of Physics, Quinnipiac University</name>
  948.      <foaf:homepage rdf:resource="https://theconversation.com/profiles/nicole-granucci-1530008"/>
  949.    </author>
  950.    <rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
  951.  </entry>
  952.  <entry>
  953.    <id>tag:theconversation.com,2011:article/233393</id>
  954.    <published>2024-12-05T13:40:09Z</published>
  955.    <updated>2024-12-05T13:40:09Z</updated>
  956.    <link rel="alternate" type="text/html" href="https://theconversation.com/some-black-holes-at-the-centers-of-galaxies-have-a-buddy-but-detecting-these-binary-pairs-isnt-easy-233393"/>
  957.    <title>Some black holes at the centers of galaxies have a buddy − but detecting these binary pairs isn’t easy</title>
  958.    <content type="html">&lt;figure&gt;&lt;img src="https://images.theconversation.com/files/633903/original/file-20241122-19-b8tdlp.jpg?ixlib=rb-4.1.0&amp;amp;rect=0%2C0%2C1200%2C671&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=496&amp;amp;fit=clip" /&gt;&lt;figcaption&gt;&lt;span class="caption"&gt;Some black holes, bound by gravity, rotate around each other, as shown in this simulated image. &lt;/span&gt; &lt;span class="attribution"&gt;&lt;a class="source" href="https://en.wikipedia.org/wiki/File:BBH_gravitational_lensing_of_gw150914.webm"&gt;Simulating eXtreme Spacetimes Lensing (SXS)&lt;/a&gt;, &lt;a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/"&gt;CC BY-SA&lt;/a&gt;&lt;/span&gt;&lt;/figcaption&gt;&lt;/figure&gt;&lt;p&gt;Every galaxy has a supermassive black hole at its center, much like every egg has a yolk. But sometimes, hens lay eggs with two yolks. In a similar way, &lt;a href="https://scholar.google.com/citations?user=XtngxB8AAAAJ&amp;amp;hl=en"&gt;astrophysicists like us&lt;/a&gt; &lt;a href="https://scholar.google.com/citations?user=e8rdVfsAAAAJ&amp;amp;hl=en"&gt;who study supermassive black holes&lt;/a&gt; expect to find binary systems – &lt;a href="https://theconversation.com/supermassive-black-hole-at-the-center-of-our-galaxy-may-have-a-friend-128295"&gt;two supermassive black holes orbiting each other&lt;/a&gt; – at the hearts of some galaxies.&lt;/p&gt;
  959.  
  960. &lt;p&gt;&lt;a href="https://theconversation.com/the-scariest-things-in-the-universe-are-black-holes-and-here-are-3-reasons-148615"&gt;Black holes&lt;/a&gt; are regions of space where gravity is so strong that not even light can escape from their vicinity. They form when the core of a massive star collapses on itself, and they act as cosmic vacuum cleaners. &lt;a href="https://theconversation.com/why-are-some-black-holes-bigger-than-others-an-astronomer-explains-how-these-celestial-vacuums-grow-217241"&gt;Supermassive black holes&lt;/a&gt; have a mass a million times that of our Sun or larger. Scientists like us study them to understand how gravity works and how galaxies form.&lt;/p&gt;
  961.  
  962. &lt;p&gt;Figuring out whether a galaxy has one or two black holes in its center isn’t as easy as cracking an egg and examining the yolk. But measuring how often these binary supermassive black holes form can help researchers understand what happens to galaxies when they merge.&lt;/p&gt;
  963.  
  964. &lt;p&gt;In a new study, our team dug through historical astronomical data dating back over a hundred years. We looked for light emitted from one galaxy that showed signs of harboring a binary supermassive black hole system.&lt;/p&gt;
  965.  
  966. &lt;h2&gt;Galactic collisions and gravitational waves&lt;/h2&gt;
  967.  
  968. &lt;p&gt;Galaxies like the Milky Way are nearly as old as the universe. Sometimes, they &lt;a href="https://doi.org/10.1093/mnras/stz159"&gt;collide with other galaxies&lt;/a&gt;, which can lead to the galaxies merging and forming a larger, more massive galaxy. &lt;/p&gt;
  969.  
  970. &lt;p&gt;The two black holes at the center of the two merging galaxies may, when close enough, form a pair bound by gravity. This pair may live for &lt;a href="https://doi.org/10.1051/0004-6361/202039859"&gt;up to hundreds of millions of years&lt;/a&gt; before the two black holes eventually merge into one. &lt;/p&gt;
  971.  
  972. &lt;figure&gt;
  973.            &lt;iframe width="440" height="260" src="https://www.youtube.com/embed/i2u-7LMhwvE?wmode=transparent&amp;amp;start=0" frameborder="0" allowfullscreen=""&gt;&lt;/iframe&gt;
  974.            &lt;figcaption&gt;&lt;span class="caption"&gt;Supermassive black holes orbiting around each other can emit gravitational waves.&lt;/span&gt;&lt;/figcaption&gt;
  975.          &lt;/figure&gt;
  976.  
  977. &lt;p&gt;Binary black holes release energy in the form of &lt;a href="https://theconversation.com/a-subtle-symphony-of-ripples-in-spacetime-astronomers-use-dead-stars-to-measure-gravitational-waves-produced-by-ancient-black-holes-208815"&gt;gravitational waves&lt;/a&gt; – ripples in space-time &lt;a href="https://theconversation.com/gravitational-wave-detector-ligo-is-back-online-after-3-years-of-upgrades-how-the-worlds-most-sensitive-yardstick-reveals-secrets-of-the-universe-204339"&gt;that specialized observatories can detect&lt;/a&gt;. According to Einstein’s &lt;a href="https://www.space.com/17661-theory-general-relativity.html"&gt;general relativity theory&lt;/a&gt;, these ripples travel at the speed of light, causing space itself to stretch and squeeze around them, kind of like a wave.&lt;/p&gt;
  978.  
  979. &lt;p&gt;&lt;a href="https://theconversation.com/using-a-detector-the-size-of-a-galaxy-astronomers-find-strongest-evidence-yet-for-gravitational-waves-from-supermassive-black-hole-pairs-208484"&gt;Pulsar timing arrays&lt;/a&gt; &lt;a href="https://www.space.com/32661-pulsars.html"&gt;use pulsars&lt;/a&gt;, which are the dense, bright cores of collapsed stars. Pulsars spin very fast. Researchers can look for gaps and anomalies in the pattern of radio waves emitted from these spinning pulsars to detect gravitational waves.&lt;/p&gt;
  980.  
  981. &lt;p&gt;While pulsar timing arrays can detect the collective gravitational wave signal from the ensemble of binaries within the past 9 billion years, they’re not yet sensitive enough to detect the gravitational wave signal from a single binary system in one galaxy. And even the most powerful telescopes can’t image these binary black holes directly. So, astronomers have to use clever indirect methods to figure out whether a galaxy has a binary supermassive black hole in its center.&lt;/p&gt;
  982.  
  983. &lt;h2&gt;Searching for signs of binary black holes&lt;/h2&gt;
  984.  
  985. &lt;p&gt;One type of indirect method involves searching for periodic signals from the centers of &lt;a href="https://imagine.gsfc.nasa.gov/science/objects/active_galaxies1.html"&gt;active galaxies&lt;/a&gt;. These are galaxies that emit significantly more energy than astronomers might expect from the amount of stars, gas and dust they contain. &lt;/p&gt;
  986.  
  987. &lt;p&gt;These galaxies emit energy from their nucleus, or center – called the &lt;a href="https://webbtelescope.org/contents/articles/what-are-active-galactic-nuclei"&gt;active galactic nucleus&lt;/a&gt;. In a process called accretion, the black hole in each active galaxy uses gravity to pull nearby gas inward. The gas speeds up as it approaches the black hole’s event horizon – like how water surrounding a whirlpool moves faster and faster as it spirals inward. &lt;/p&gt;
  988.  
  989. &lt;p&gt;As the gas heats up, it glows brightly in optical, ultraviolet and X-ray light. Active galactic nuclei are some of the most luminous objects in the universe.&lt;/p&gt;
  990.  
  991. &lt;p&gt;Some active galactic nuclei can launch jets, which are particle beams accelerated to near the speed of light. When these jets line up with our observatories’ lines of sight, they appear extremely bright. They’re like cosmic lighthouses.&lt;/p&gt;
  992.  
  993. &lt;p&gt;Some active galactic nuclei have periodic light signals that get bright, fade and then get bright again. This unique signal could come from the cyclical motion of two supermassive black holes inside, and it suggests to astronomers to look for a binary black hole system in that galaxy.&lt;/p&gt;
  994.  
  995. &lt;h2&gt;On the hunt for a binary black hole system&lt;/h2&gt;
  996.  
  997. &lt;p&gt;Our team studied one such active galactic nucleus, &lt;a href="http://tevcat.uchicago.edu/?mode=1&amp;amp;showsrc=102"&gt;called PG 1553+153&lt;/a&gt;. The light from this object gets brighter and dimmer &lt;a href="https://iopscience.iop.org/article/10.1088/2041-8205/813/2/L41"&gt;about every 2.2 years&lt;/a&gt;.&lt;/p&gt;
  998.  
  999. &lt;p&gt;These periodic variations suggest that PG 1553+153 &lt;a href="https://doi.org/10.1093/mnras/stad3246"&gt;has a supermassive black hole binary inside&lt;/a&gt;. But a binary isn’t the only explanation for this variation. Other phenomena, such as wobbly jets or changes in the flow of material around the black hole, could also explain this pattern without the presence of a binary black hole, so we had to rule those out.&lt;/p&gt;
  1000.  
  1001. &lt;p&gt;To understand whether the PG 1553+153 system’s light emission patterns came from a binary black hole, &lt;a href="https://journals.aps.org/prd/abstract/10.1103/PhysRevD.106.103010"&gt;we simulated how&lt;/a&gt; binary supermassive black holes collect gas. Our models suggested that sometimes, when the black holes pull in gas, dense clumps of gas collect around the outside of the hole. &lt;/p&gt;
  1002.  
  1003. &lt;p&gt;We calculated that the time it takes for these clumps to orbit around the two black holes should be five to 10 times longer than the time it takes for the two black holes to circle each other.&lt;/p&gt;
  1004.  
  1005. &lt;p&gt;So, we finally had a clear prediction that we could test. If a binary black hole system caused the 2.2-year periodic variation in PG 1553+153, then we should also be able to see a longer pattern of variation, about every 10 to 20 years, when the clumps of gas circle around the black holes. &lt;/p&gt;
  1006.  
  1007. &lt;p&gt;But to see whether this was really a pattern, we needed to watch it repeat for four to five cycles. For PG 1553+153, that would be 40 to 100 years.&lt;/p&gt;
  1008.  
  1009.  
  1010.  
  1011. &lt;p&gt;Astronomers have observed the sky &lt;a href="https://pages.uoregon.edu/jschombe/ast121/lectures/lec02.html"&gt;for hundreds of years&lt;/a&gt;. But the era of digital astronomy, where astronomical images are recorded on computers and saved in databases, is very recent – only since the year 2000 or so. &lt;/p&gt;
  1012.  
  1013. &lt;p&gt;Before then, starting around 1850, astronomers recorded images of the sky on photographic plates. These are flat pieces of glass coated with a light-sensitive chemical layer traditionally used in photography. Many observatories around the world have photographic images of the night sky dating back to more than a hundred years ago. Before that, astronomers would sketch what the sky looked like in their notebooks.  &lt;/p&gt;
  1014.  
  1015. &lt;p&gt;&lt;a href="https://dasch.cfa.harvard.edu/"&gt;Projects like DASCH&lt;/a&gt;, Digital Access to a Sky Century at Harvard, have started digitalizing &lt;a href="https://nautil.us/these-astronomical-glass-plates-made-history-235766/"&gt;photographic plates from a few observatories&lt;/a&gt; to make them available for scientists and nonscientists alike. &lt;/p&gt;
  1016.  
  1017. &lt;p&gt;Our team learned that the DASCH database provided data on PG 1553+153 dating back to 1900 – more than 120 years. We used this dataset to see whether we could see a pattern repeating every 10 to 20 years. &lt;/p&gt;
  1018.  
  1019. &lt;p&gt;Somewhat to our surprise, &lt;a href="https://doi.org/10.3847/1538-4357/ad310a"&gt;we found a 20-year pattern&lt;/a&gt; that adds more evidence to our theory that there’s a binary system at the core of PG 1553+153. The detection of this second pattern also helped us figure out that the masses of the two supermassive black holes are in a 2.5:1 ratio – with one 2½ times as large as the other – and that their orbit is nearly circular.&lt;/p&gt;
  1020.  
  1021. &lt;p&gt;While this historical data makes us more confident that there are two supermassive black holes in PG 1553+153, we still can’t say for sure. The final confirmation might need to wait until pulsar timing arrays become sensitive enough to detect the gravitational waves coming from PG 1553+153.&lt;/p&gt;&lt;img src="https://counter.theconversation.com/content/233393/count.gif" alt="The Conversation" width="1" height="1" /&gt;
  1022. &lt;p class="fine-print"&gt;&lt;em&gt;&lt;span&gt;Marco Ajello receives funding from NASA and NSF.&lt;/span&gt;&lt;/em&gt;&lt;/p&gt;&lt;p class="fine-print"&gt;&lt;em&gt;&lt;span&gt;Jonathan Zrake receives funding from NASA and NSF.&lt;/span&gt;&lt;/em&gt;&lt;/p&gt;</content>
  1023.    <summary>Most objects in the universe have been around for way longer than modern astronomy – digging into historical records can help scientists shed light on a cosmic mystery.</summary>
  1024.    <author>
  1025.      <name>Marco Ajello, Professor of Physics and Astronomy, Clemson University</name>
  1026.      <foaf:homepage rdf:resource="https://theconversation.com/profiles/marco-ajello-1544227"/>
  1027.    </author>
  1028.    <author>
  1029.      <name>Jonathan Zrake, Assistant Professor of Physics, Clemson University</name>
  1030.      <foaf:homepage rdf:resource="https://theconversation.com/profiles/jonathan-zrake-2240746"/>
  1031.    </author>
  1032.    <rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
  1033.  </entry>
  1034.  <entry>
  1035.    <id>tag:theconversation.com,2011:article/244157</id>
  1036.    <published>2024-12-03T00:01:50Z</published>
  1037.    <updated>2024-12-03T00:01:50Z</updated>
  1038.    <link rel="alternate" type="text/html" href="https://theconversation.com/to-map-the-vibration-of-the-universe-astronomers-built-a-detector-the-size-of-the-galaxy-244157"/>
  1039.    <title>To map the vibration of the universe, astronomers built a detector the size of the galaxy</title>
  1040.    <content type="html">&lt;figure&gt;&lt;img src="https://images.theconversation.com/files/633168/original/file-20241120-19-zbny5g.jpg?ixlib=rb-4.1.0&amp;amp;rect=0%2C0%2C4107%2C2312&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=496&amp;amp;fit=clip" /&gt;&lt;figcaption&gt;&lt;span class="caption"&gt;&lt;/span&gt; &lt;span class="attribution"&gt;&lt;span class="source"&gt;Carl Knox, OzGrav, Swinburne University of Technology and South African Radio Astronomy Observatory (SARAO)&lt;/span&gt;&lt;/span&gt;&lt;/figcaption&gt;&lt;/figure&gt;&lt;p&gt;Using the largest gravitational wave detector ever made, we have confirmed earlier reports that the fabric of the universe is constantly vibrating. This background rumble is likely caused by collisions between the enormous black holes that reside in the hearts of galaxies.&lt;/p&gt;
  1041.  
  1042. &lt;p&gt;The results from our detector – an array of rapidly spinning neutron stars spread across the galaxy – show this “gravitational wave background” may be louder than previously thought. We have also made the most detailed maps yet of gravitational waves across the sky, and found an intriguing “hot spot” of activity in the Southern Hemisphere.&lt;/p&gt;
  1043.  
  1044. &lt;p&gt;Our &lt;a href="https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/stae2571/7912548"&gt;research&lt;/a&gt; is &lt;a href="https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/stae2572/7912547"&gt;published&lt;/a&gt; today in &lt;a href="https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/stae2573/7912549"&gt;three papers&lt;/a&gt; in the Monthly Notices of the Royal Astronomical Society.&lt;/p&gt;
  1045.  
  1046. &lt;h2&gt;Ripples in space and time&lt;/h2&gt;
  1047.  
  1048. &lt;p&gt;&lt;a href="https://theconversation.com/explainer-what-are-gravitational-waves-53239"&gt;Gravitational waves&lt;/a&gt; are ripples in the fabric of space and time. They are created when incredibly dense and massive objects orbit or collide with each other. &lt;/p&gt;
  1049.  
  1050. &lt;p&gt;The densest and most massive objects in the universe are black holes, the remnants of dead stars. One of the only ways to study black holes is by searching for the gravitational waves they emit when they move near each other. &lt;/p&gt;
  1051.  
  1052. &lt;p&gt;Just like light, gravitational waves are emitted in a spectrum. The most massive black holes emit the slowest and most powerful waves – but to study them, we need a detector the size of our galaxy.&lt;/p&gt;
  1053.  
  1054. &lt;p&gt;The high-frequency gravitational waves created by collisions between relatively small black holes can be picked up with Earth-based detectors, and they were first observed in 2015. However, &lt;a href="https://iopscience.iop.org/article/10.3847/1538-4357/ad36be"&gt;evidence&lt;/a&gt; for the existence of the slower, more powerful waves wasn’t found until last year.&lt;/p&gt;
  1055.  
  1056. &lt;p&gt;Several groups of astronomers around the world have assembled galactic-scale gravitational wave detectors by closely observing the behaviour of groups of particular kinds of stars. Our experiment, the &lt;a href="https://mpta-gw.github.io/"&gt;MeerKAT Pulsar Timing Array&lt;/a&gt;, is the largest of these galactic-scale detectors.&lt;/p&gt;
  1057.  
  1058. &lt;p&gt;Today we have announced further evidence for low-frequency gravitational waves, but with some intriguing differences from earlier results. In just a third of the time of other experiments, we’ve found a signal that hints at a more active universe than anticipated. &lt;/p&gt;
  1059.  
  1060. &lt;p&gt;We have also been able to map the cosmic architecture left behind by merging galaxies more accurately than ever before.&lt;/p&gt;
  1061.  
  1062. &lt;h2&gt;Black holes, galaxies and pulsars&lt;/h2&gt;
  1063.  
  1064. &lt;p&gt;At the centre of most galaxies, scientists believe, lives a gargantuan object known as a supermassive black hole. Despite their enormous mass – billions of times the mass of our Sun – these cosmic giants are difficult to study.&lt;/p&gt;
  1065.  
  1066. &lt;p&gt;Astronomers have known about supermassive black holes for decades, but only directly observed one &lt;a href="https://theconversation.com/first-black-hole-photo-confirms-einsteins-theory-of-relativity-115167"&gt;for the first time in 2019&lt;/a&gt;.&lt;/p&gt;
  1067.  
  1068. &lt;p&gt;When two galaxies merge, the black holes at their centres begin to spiral towards each other. In this process they send out slow, powerful gravitational waves that give us an opportunity to study them.&lt;/p&gt;
  1069.  
  1070. &lt;p&gt;We do this using another group of exotic cosmic objects: &lt;a href="https://theconversation.com/fifty-years-ago-jocelyn-bell-discovered-pulsars-and-changed-our-view-of-the-universe-88083"&gt;pulsars&lt;/a&gt;. These are extremely dense stars made mainly of neutrons, which may be around the size of a city but twice as heavy as the Sun. &lt;/p&gt;
  1071.  
  1072. &lt;p&gt;Pulsars spin hundreds of times a second. As they rotate, they act like lighthouses, hitting Earth with pulses of radiation from thousands of light years away. For some pulsars, we can predict when that pulse should hit us to within nanoseconds. &lt;/p&gt;
  1073.  
  1074. &lt;p&gt;Our gravitational wave detectors make use of this fact. If we observe many pulsars over the same period of time, and we’re wrong about when the pulses hit us in a very specific way, we know a gravitational wave is stretching or squeezing the space between the Earth and the pulsars. &lt;/p&gt;
  1075.  
  1076. &lt;p&gt;However, instead of seeing just one wave, we expect to see a cosmic ocean full of waves criss-crossing in all directions – the echoing ripples of all the galactic mergers in the history of the universe. We call this the gravitational wave background. &lt;/p&gt;
  1077.  
  1078. &lt;h2&gt;A surprisingly loud signal – and an intriguing ‘hot spot’&lt;/h2&gt;
  1079.  
  1080. &lt;p&gt;To detect the gravitational wave background, we used the &lt;a href="https://theconversation.com/meerkat-the-south-african-radio-telescope-thats-transformed-our-understanding-of-the-cosmos-227616"&gt;MeerKAT radio telescope&lt;/a&gt; in South Africa. MeerKAT is one of the most sensitive radio telescopes in the world. &lt;/p&gt;
  1081.  
  1082. &lt;p&gt;As part of the MeerKAT Pulsar Timing Array, it has been observing a group of 83 pulsars for about five years, precisely measuring when their pulses arrive at Earth. This led us to find a pattern associated with a gravitational wave background, only it’s a bit different from what other experiments have found. &lt;/p&gt;
  1083.  
  1084. &lt;p&gt;The pattern, which represents how space and time between Earth and the pulsars is changed by gravitational waves passing between them, is more powerful than expected.&lt;/p&gt;
  1085.  
  1086. &lt;p&gt;This might mean there are more supermassive black holes orbiting each other than we thought. If so, this raises more questions – because our existing theories suggest there should be fewer supermassive black holes than we seem to be seeing.&lt;/p&gt;
  1087.  
  1088. &lt;p&gt;The size of our detector, and the sensitivity of the MeerKAT telescope, means we can assess the background with extreme precision. This allowed us to create the most detailed maps of the gravitational wave background to date. Mapping the background in this way is essential for understanding the cosmic architecture of our universe. &lt;/p&gt;
  1089.  
  1090. &lt;p&gt;It may even lead us to the ultimate source of the gravitational wave signals we observe. While we think it’s likely the background emerges from the interactions of these colossal black holes, it could also stem from changes in the early, energetic universe following the Big Bang – or perhaps even more exotic events.&lt;/p&gt;
  1091.  
  1092. &lt;figure class="align-center zoomable"&gt;
  1093.            &lt;a href="https://images.theconversation.com/files/635546/original/file-20241202-15-3h6qa5.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=1000&amp;amp;fit=clip"&gt;&lt;img alt="An oval shaped diagram marked with coordinates, showing a purple background with orange and yellow blobs. There is a particularly bright blob at the bottom right." src="https://images.theconversation.com/files/635546/original/file-20241202-15-3h6qa5.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;fit=clip" srcset="https://images.theconversation.com/files/635546/original/file-20241202-15-3h6qa5.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=304&amp;amp;fit=crop&amp;amp;dpr=1 600w, https://images.theconversation.com/files/635546/original/file-20241202-15-3h6qa5.png?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=304&amp;amp;fit=crop&amp;amp;dpr=2 1200w, https://images.theconversation.com/files/635546/original/file-20241202-15-3h6qa5.png?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=304&amp;amp;fit=crop&amp;amp;dpr=3 1800w, https://images.theconversation.com/files/635546/original/file-20241202-15-3h6qa5.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=382&amp;amp;fit=crop&amp;amp;dpr=1 754w, https://images.theconversation.com/files/635546/original/file-20241202-15-3h6qa5.png?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=382&amp;amp;fit=crop&amp;amp;dpr=2 1508w, https://images.theconversation.com/files/635546/original/file-20241202-15-3h6qa5.png?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=382&amp;amp;fit=crop&amp;amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"&gt;&lt;/a&gt;
  1094.            &lt;figcaption&gt;
  1095.              &lt;span class="caption"&gt;A map of the gravitational wave background across the sky, including a mysterious ‘hot spot’ in the southern hemisphere.&lt;/span&gt;
  1096.              &lt;span class="attribution"&gt;&lt;a class="source" href="https://doi.org/10.1093/mnras/stae2573"&gt;Grunthal &amp;amp; Nathan et al. / MNRAS&lt;/a&gt;&lt;/span&gt;
  1097.            &lt;/figcaption&gt;
  1098.          &lt;/figure&gt;
  1099.  
  1100. &lt;p&gt;The maps we’ve created show an intriguing “hot spot” of gravitational wave activity in the Southern Hemisphere sky. This kind of irregularity supports the idea of a background created by supermassive black holes rather than other alternatives.&lt;/p&gt;
  1101.  
  1102. &lt;p&gt;However, creating a galactic-sized detector is incredibly complex, and it’s too early to say if this is genuine or a statistical anomaly.&lt;/p&gt;
  1103.  
  1104. &lt;p&gt;To confirm our findings, we are working to combine our new data with results from other international collaborations under the banner of the &lt;a href="https://ipta4gw.org/"&gt;International Pulsar Timing Array&lt;/a&gt;.&lt;/p&gt;&lt;img src="https://counter.theconversation.com/content/244157/count.gif" alt="The Conversation" width="1" height="1" /&gt;
  1105. &lt;p class="fine-print"&gt;&lt;em&gt;&lt;span&gt;Matthew Miles is affiliated with the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav), the MeerKAT Pulsar Timing Array, the Parkes Pulsar Timing Array and the International Pulsar Timing Array. He receives funding from the Australian Research Council.&lt;/span&gt;&lt;/em&gt;&lt;/p&gt;&lt;p class="fine-print"&gt;&lt;em&gt;&lt;span&gt;Rowina Nathan is affiliated with the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav), the MeerKAT Pulsar Timing Array, the Parkes Pulsar Timing Array and the International Pulsar Timing Array. She receives funding from the Australian Research Council. &lt;/span&gt;&lt;/em&gt;&lt;/p&gt;</content>
  1106.    <summary>A new effort to map the rumblings in spacetime caused by enormous black hole collisions paints a surprisingly loud and lopsided picture of the universe.</summary>
  1107.    <author>
  1108.      <name>Matthew Miles, Postdoctoral Researcher in Astrophysics, Swinburne University of Technology</name>
  1109.      <foaf:homepage rdf:resource="https://theconversation.com/profiles/matthew-miles-2253712"/>
  1110.    </author>
  1111.    <author>
  1112.      <name>Rowina Nathan, Astrophysicist, Monash University</name>
  1113.      <foaf:homepage rdf:resource="https://theconversation.com/profiles/rowina-nathan-2263669"/>
  1114.    </author>
  1115.    <rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
  1116.  </entry>
  1117.  <entry>
  1118.    <id>tag:theconversation.com,2011:article/244920</id>
  1119.    <published>2024-12-02T02:37:34Z</published>
  1120.    <updated>2024-12-02T02:37:34Z</updated>
  1121.    <link rel="alternate" type="text/html" href="https://theconversation.com/astronomers-have-pinpointed-the-origin-of-mysterious-repeating-radio-bursts-from-space-244920"/>
  1122.    <title>Astronomers have pinpointed the origin of mysterious repeating radio bursts from space</title>
  1123.    <content type="html">&lt;figure&gt;&lt;img src="https://images.theconversation.com/files/635241/original/file-20241129-15-jh3e1v.jpg?ixlib=rb-4.1.0&amp;amp;rect=0%2C0%2C1920%2C1439&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=496&amp;amp;fit=clip" /&gt;&lt;figcaption&gt;&lt;span class="caption"&gt;An artist&amp;#39;s impression of the exotic binary star system AR Scorpii.&lt;/span&gt; &lt;span class="attribution"&gt;&lt;a class="source" href="https://www.eso.org/public/images/eso1627a/"&gt;Mark Garlick/University of Warwick/ESO&lt;/a&gt;, &lt;a class="license" href="http://creativecommons.org/licenses/by/4.0/"&gt;CC BY&lt;/a&gt;&lt;/span&gt;&lt;/figcaption&gt;&lt;/figure&gt;&lt;p&gt;Slowly repeating bursts of intense radio waves from space have puzzled astronomers since they were discovered in 2022. &lt;/p&gt;
  1124.  
  1125. &lt;p&gt;In &lt;a href="https://iopscience.iop.org/article/10.3847/2041-8213/ad890e/pdf"&gt;new research&lt;/a&gt;, we have for the first time tracked one of these pulsating signals back to its source: a common kind of lightweight star called a red dwarf, likely in a binary orbit with a white dwarf, the core of another star that exploded long ago.&lt;/p&gt;
  1126.  
  1127. &lt;h2&gt;A slowly pulsing mystery&lt;/h2&gt;
  1128.  
  1129. &lt;p&gt;In 2022, our team made &lt;a href="https://theconversation.com/this-object-in-space-flashed-brilliantly-for-3-months-then-disappeared-astronomers-are-intrigued-175240"&gt;an amazing discovery&lt;/a&gt;: periodic radio pulsations that repeated every 18 minutes, emanating from space. The pulses outshone everything nearby, &lt;a href="https://theconversation.com/this-object-in-space-flashed-brilliantly-for-3-months-then-disappeared-astronomers-are-intrigued-175240"&gt;flashed brilliantly for three months&lt;/a&gt;, then disappeared.&lt;/p&gt;
  1130.  
  1131. &lt;p&gt;We know some repeating radio signals come from a kind of neutron star called a radio pulsar, which spins rapidly (typically once a second or faster), beaming out radio waves like a lighthouse. The trouble is, our current theories say a pulsar spinning only once every 18 minutes should &lt;em&gt;not&lt;/em&gt; produce radio waves. &lt;/p&gt;
  1132.  
  1133. &lt;p&gt;So we thought our 2022 discovery could point to new and exciting physics – or help explain exactly how pulsars emit radiation, which despite 50 years of research is still not understood very well.&lt;/p&gt;
  1134.  
  1135. &lt;p&gt;More slowly blinking radio sources &lt;a href="https://theconversation.com/a-mysterious-interstellar-radio-signal-has-been-blinking-on-and-off-every-22-minutes-for-over-30-years-205237"&gt;have been discovered&lt;/a&gt; since then. There are now about ten known “long-period radio transients”. &lt;/p&gt;
  1136.  
  1137. &lt;p&gt;However, just finding more hasn’t been enough to solve the mystery.&lt;/p&gt;
  1138.  
  1139. &lt;h2&gt;Searching the outskirts of the galaxy&lt;/h2&gt;
  1140.  
  1141. &lt;p&gt;Until now, every one of these sources has been found deep in the heart of the Milky Way. &lt;/p&gt;
  1142.  
  1143. &lt;p&gt;This makes it very hard to figure out what kind of star or object produces the radio waves, because there are thousands of stars in a small area. Any one of them could be responsible for the signal, or none of them.&lt;/p&gt;
  1144.  
  1145. &lt;p&gt;So, we started a campaign to scan the skies with the &lt;a href="https://www.mwatelescope.org"&gt;Murchison Widefield Array&lt;/a&gt; radio telescope in Western Australia, which can observe 1,000 square degrees of the sky every minute. An undergraduate student at Curtin University, Csanád Horváth, processed data covering half of the sky, looking for these elusive signals in more sparsely populated regions of the Milky Way.&lt;/p&gt;
  1146.  
  1147. &lt;figure class="align-center zoomable"&gt;
  1148.            &lt;a href="https://images.theconversation.com/files/635414/original/file-20241201-15-1jrnw.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=1000&amp;amp;fit=clip"&gt;&lt;img alt="A collection of 16 dipole antennas on red outback sands surrounded by shrubs" src="https://images.theconversation.com/files/635414/original/file-20241201-15-1jrnw.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;fit=clip" srcset="https://images.theconversation.com/files/635414/original/file-20241201-15-1jrnw.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=447&amp;amp;fit=crop&amp;amp;dpr=1 600w, https://images.theconversation.com/files/635414/original/file-20241201-15-1jrnw.jpg?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=447&amp;amp;fit=crop&amp;amp;dpr=2 1200w, https://images.theconversation.com/files/635414/original/file-20241201-15-1jrnw.jpg?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=447&amp;amp;fit=crop&amp;amp;dpr=3 1800w, https://images.theconversation.com/files/635414/original/file-20241201-15-1jrnw.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=561&amp;amp;fit=crop&amp;amp;dpr=1 754w, https://images.theconversation.com/files/635414/original/file-20241201-15-1jrnw.jpg?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=561&amp;amp;fit=crop&amp;amp;dpr=2 1508w, https://images.theconversation.com/files/635414/original/file-20241201-15-1jrnw.jpg?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=561&amp;amp;fit=crop&amp;amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"&gt;&lt;/a&gt;
  1149.            &lt;figcaption&gt;
  1150.              &lt;span class="caption"&gt;One element of the Murchison Widefield Array, a radio telescope in Western Australia that observes the sky at low radio frequencies.&lt;/span&gt;
  1151.              &lt;span class="attribution"&gt;&lt;a class="source" href="https://www.mwatelescope.org/media/"&gt;ICRAR / Curtin University&lt;/a&gt;&lt;/span&gt;
  1152.            &lt;/figcaption&gt;
  1153.          &lt;/figure&gt;
  1154.  
  1155. &lt;p&gt;And sure enough, we found a new source! Dubbed GLEAM-X J0704-37, it produces minute-long pulses of radio waves, just like other long-period radio transients. However, these pulses repeat only once every 2.9 hours, making it the slowest long-period radio transient found so far.&lt;/p&gt;
  1156.  
  1157. &lt;h2&gt;Where are the radio waves coming from?&lt;/h2&gt;
  1158.  
  1159. &lt;p&gt;We performed follow-up observations with the &lt;a href="https://www.sarao.ac.za/science/meerkat/about-meerkat/"&gt;MeerKAT telescope&lt;/a&gt; in South Africa, the most sensitive radio telescope in the southern hemisphere. These pinpointed the location of the radio waves precisely: they were coming from a red dwarf star. These stars are incredibly common, making up 70% of the stars in the Milky Way, but they are so faint that not a single one is visible to the naked eye.&lt;/p&gt;
  1160.  
  1161. &lt;figure class="align-center zoomable"&gt;
  1162.            &lt;a href="https://images.theconversation.com/files/635240/original/file-20241129-15-znzd86.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=1000&amp;amp;fit=clip"&gt;&lt;img alt="Greyscale image of six stars, two of which are encircled by a magenta circle, and one of which is pinpointed by a cyan circle." src="https://images.theconversation.com/files/635240/original/file-20241129-15-znzd86.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;fit=clip" srcset="https://images.theconversation.com/files/635240/original/file-20241129-15-znzd86.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=533&amp;amp;fit=crop&amp;amp;dpr=1 600w, https://images.theconversation.com/files/635240/original/file-20241129-15-znzd86.png?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=533&amp;amp;fit=crop&amp;amp;dpr=2 1200w, https://images.theconversation.com/files/635240/original/file-20241129-15-znzd86.png?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=533&amp;amp;fit=crop&amp;amp;dpr=3 1800w, https://images.theconversation.com/files/635240/original/file-20241129-15-znzd86.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=669&amp;amp;fit=crop&amp;amp;dpr=1 754w, https://images.theconversation.com/files/635240/original/file-20241129-15-znzd86.png?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=669&amp;amp;fit=crop&amp;amp;dpr=2 1508w, https://images.theconversation.com/files/635240/original/file-20241129-15-znzd86.png?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=669&amp;amp;fit=crop&amp;amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"&gt;&lt;/a&gt;
  1163.            &lt;figcaption&gt;
  1164.              &lt;span class="caption"&gt;The source of the radio waves, as seen by the MWA at low resolution (magenta circle) and MeerKAT at high resolution (cyan circle). The white circles are all stars in our own Galaxy.&lt;/span&gt;
  1165.              &lt;span class="attribution"&gt;&lt;span class="source"&gt;Hurley-Walker et al. 2024 / Astrophysical Journal Letters&lt;/span&gt;&lt;/span&gt;
  1166.            &lt;/figcaption&gt;
  1167.          &lt;/figure&gt;
  1168.  
  1169. &lt;p&gt;Combining historical observations from the Murchison Widefield Array and new MeerKAT monitoring data, we found that the pulses arrive a little earlier and a little later in a repeating pattern. This probably indicates that the radio emitter isn’t the red dwarf itself, but rather an unseen object in a binary orbit with it.&lt;/p&gt;
  1170.  
  1171. &lt;p&gt;Based on previous studies of the evolution of stars, we think this invisible radio emitter is most likely to be a white dwarf, which is the final endpoint of small to medium-sized stars like our own Sun. If it were a neutron star or a black hole, the explosion that created it would have been so large it should have disrupted the orbit.&lt;/p&gt;
  1172.  
  1173. &lt;h2&gt;It takes two to tango&lt;/h2&gt;
  1174.  
  1175. &lt;p&gt;So how do a red dwarf and a white dwarf generate a radio signal? &lt;/p&gt;
  1176.  
  1177. &lt;p&gt;The red dwarf probably produces a stellar wind of charged particles, just like our Sun does. When the wind hits the white dwarf’s magnetic field, it would be accelerated, producing radio waves. &lt;/p&gt;
  1178.  
  1179. &lt;p&gt;This could be similar to how the Sun’s stellar wind interacts with Earth’s magnetic field to produce beautiful &lt;a href="https://theconversation.com/i-heard-theres-an-aurora-coming-how-do-i-check-235869"&gt;aurora&lt;/a&gt;, and also &lt;a href="https://www.gi.alaska.edu/alaska-science-forum/radio-waves-aurora"&gt;low-frequency radio waves&lt;/a&gt;.&lt;/p&gt;
  1180.  
  1181. &lt;figure&gt;
  1182.            &lt;iframe width="440" height="260" src="https://www.youtube.com/embed/YdFi2qX9Hek?wmode=transparent&amp;amp;start=0" frameborder="0" allowfullscreen=""&gt;&lt;/iframe&gt;
  1183.            &lt;figcaption&gt;&lt;span class="caption"&gt;An artist’s impression of the AR Sco system: a binary red dwarf and white dwarf that interact to produce radio emission.&lt;/span&gt;&lt;/figcaption&gt;
  1184.          &lt;/figure&gt;
  1185.  
  1186. &lt;p&gt;We already know of a few systems like this, such as &lt;a href="https://www.nature.com/articles/s41550-016-0029"&gt;AR Scorpii&lt;/a&gt;, where variations in the brightness of the red dwarf imply that the companion white dwarf is hitting it with a powerful beam of radio waves every two minutes. None of these systems are as bright or as slow as the long-period radio transients, but maybe as we find more examples, we will work out a unifying physical model that explains all of them. &lt;/p&gt;
  1187.  
  1188. &lt;p&gt;On the other hand, there may be &lt;a href="https://arxiv.org/html/2401.12494v1"&gt;many&lt;/a&gt; &lt;a href="https://ui.adsabs.harvard.edu/abs/2024PhRvD.109f3004B/abstract"&gt;different&lt;/a&gt; &lt;a href="https://arxiv.org/abs/2406.04135"&gt;kinds&lt;/a&gt; of system that can produce long-period radio pulsations.&lt;/p&gt;
  1189.  
  1190. &lt;p&gt;Either way, we’ve learned the power of expecting the unexpected – and we’ll keep scanning the skies to solve this cosmic mystery.&lt;/p&gt;&lt;img src="https://counter.theconversation.com/content/244920/count.gif" alt="The Conversation" width="1" height="1" /&gt;
  1191. &lt;p class="fine-print"&gt;&lt;em&gt;&lt;span&gt;Natasha Hurley-Walker is supported by an Australian Research Council Future Fellowship (project number FT190100231) funded by the Australian Government.&lt;/span&gt;&lt;/em&gt;&lt;/p&gt;</content>
  1192.    <summary>By searching sparsely populated regions of the galaxy, astronomers have for the first time found the source of a kind of signal that has puzzled them for years.</summary>
  1193.    <author>
  1194.      <name>Natasha Hurley-Walker, Radio Astronomer, Curtin University</name>
  1195.      <foaf:homepage rdf:resource="https://theconversation.com/profiles/natasha-hurley-walker-197768"/>
  1196.    </author>
  1197.    <rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
  1198.  </entry>
  1199.  <entry>
  1200.    <id>tag:theconversation.com,2011:article/242952</id>
  1201.    <published>2024-11-20T10:41:11Z</published>
  1202.    <updated>2024-11-20T10:41:11Z</updated>
  1203.    <link rel="alternate" type="text/html" href="https://theconversation.com/its-100-years-since-we-learned-the-milky-way-is-not-the-only-galaxy-242952"/>
  1204.    <title>It’s 100 years since we learned the Milky Way is not the only galaxy</title>
  1205.    <content type="html">&lt;figure&gt;&lt;img src="https://images.theconversation.com/files/632939/original/file-20241119-15-ypv031.jpg?ixlib=rb-4.1.0&amp;amp;rect=28%2C0%2C9357%2C6979&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=496&amp;amp;fit=clip" /&gt;&lt;figcaption&gt;&lt;span class="caption"&gt;Edwin Hubble&amp;#39;s work showed that Andromeda (pictured) was a separate galaxy outside the Milky Way.&lt;/span&gt; &lt;span class="attribution"&gt;&lt;a class="source" href="https://photojournal.jpl.nasa.gov/catalog/PIA15416"&gt;Nasa/JPL-Caltech&lt;/a&gt;&lt;/span&gt;&lt;/figcaption&gt;&lt;/figure&gt;&lt;p&gt;On Sunday November 23 1924, 100 years ago this month, readers perusing page six of the New York Times would have found &lt;a href="https://www.nytimes.com/1924/11/23/archives/finds-spiral-nebulae-are-stellar-systems-dr-hubbell-confirms-view.html"&gt;an intriguing article&lt;/a&gt;, amid several large adverts for fur coats. The headline read: Finds Spiral Nebulae are Stellar Systems: “Dr Hubbell Confirms View That They Are ‘Island Universes’; Similar to Our Own”.&lt;/p&gt;
  1206.  
  1207. &lt;p&gt;The American astronomer at the centre of the article, &lt;a href="https://www.britannica.com/biography/Edwin-Hubble"&gt;Dr Edwin Powell Hubble&lt;/a&gt;, was probably bemused by the misspelling of his name. But the story detailed a groundbreaking discovery: Hubble had found that two &lt;a href="https://www.e-education.psu.edu/astro801/content/l9_p2.html"&gt;spiral-shaped nebulae&lt;/a&gt;, objects made up of gas and stars, which were previously thought to reside within our Milky Way galaxy, were located outside it. &lt;/p&gt;
  1208.  
  1209. &lt;p&gt;These objects were actually the &lt;a href="https://science.nasa.gov/mission/hubble/science/explore-the-night-sky/hubble-messier-catalog/messier-31/"&gt;Andromeda&lt;/a&gt; and &lt;a href="https://science.nasa.gov/mission/hubble/science/explore-the-night-sky/hubble-messier-catalog/messier-33/"&gt;Messier 33&lt;/a&gt; galaxies, the closest large galaxies to our Milky Way. Today, up to several trillion galaxies are estimated to fill the Universe, based on observations of tens of millions of galaxies.&lt;/p&gt;
  1210.  
  1211. &lt;p&gt;Four years before Hubble’s announcement, an event called &lt;a href="https://www.skyatnightmagazine.com/space-science/great-debate-1920-curtis-shapley-astronomy"&gt;“the great debate”&lt;/a&gt; had taken place in Washington DC between the American astronomers &lt;a href="https://www.britannica.com/biography/Harlow-Shapley"&gt;Harlow Shapley&lt;/a&gt; and &lt;a href="https://apod.nasa.gov/debate/1920/curtis_obit.html"&gt;Heber Curtis&lt;/a&gt;. Shapley had recently shown the Milky Way to be larger than previously measured. Shapley argued that it could accommodate spiral nebulae within it. Curtis, on the other hand, advocated for the existence of galaxies beyond the Milky Way. &lt;/p&gt;
  1212.  
  1213. &lt;p&gt;In hindsight, and ignoring certain details, Curtis won the debate. However, the method Shapley used to measure distances across the Milky Way was critical to Hubble’s discovery, and was inherited from the work of a pioneering US astronomer: &lt;a href="https://www.britannica.com/biography/Henrietta-Swan-Leavitt"&gt;Henrietta Swan Leavitt&lt;/a&gt;.&lt;/p&gt;
  1214.  
  1215.  
  1216.  
  1217. &lt;h2&gt;Measuring distances to stars&lt;/h2&gt;
  1218.  
  1219. &lt;p&gt;In 1893, a young Leavitt was hired as a “computer” to analyse images from telescope observations at Harvard College Observatory, Massachusetts. Leavitt studied photographic plates from telescope observations of another galaxy called the Small Magellanic Cloud carried out by other observatory researchers. &lt;/p&gt;
  1220.  
  1221. &lt;p&gt;Leavitt was searching for stars whose brightness changed over time. From over a thousand variable (changing) stars, she identified 25 were of a type known as &lt;a href="https://www.britannica.com/science/Cepheid-variable"&gt;Cepheids&lt;/a&gt;, publishing the results in 1912. &lt;/p&gt;
  1222.  
  1223. &lt;p&gt;The brightness of Cepheid stars changes with time, so they appear to pulse. Leavitt found a consistent relationship: Cepheids that pulsed more slowly were intrinsically brighter (more luminous) than those pulsing more quickly. This was dubbed the &lt;a href="https://astrolab.awh.durham.ac.uk/cepheid.html"&gt;“period-luminosity relationship”&lt;/a&gt;.&lt;/p&gt;
  1224.  
  1225. &lt;p&gt;Other astronomers realised the significance of Leavitt’s work: the relationship could be used to &lt;a href="https://www.atnf.csiro.au/outreach//education/senior/astrophysics/photometry_magnitude.html"&gt;work out&lt;/a&gt; &lt;a href="https://www.atnf.csiro.au/outreach/education/senior/astrophysics/variable_cepheids.html"&gt;distances to stars&lt;/a&gt;. While a student at Princeton University, Shapley used the period-luminosity relationship to estimate distances to other Cepheids across the Milky Way. This is how Shapley reached his estimate for our galaxy’s size.&lt;/p&gt;
  1226.  
  1227.  
  1228.  
  1229. &lt;p&gt;But, in order for astronomers to be sure about distances within our galaxy, they needed a more direct way to measure distances to Cepheids. The &lt;a href="https://lco.global/spacebook/distance/parallax-and-distance-measurement/"&gt;stellar parallax method&lt;/a&gt; is another way to measure cosmic distances, but it only works for nearby stars. As the Earth orbits the Sun, a nearby star appears to move relative to more distant background stars. This apparent motion is known as stellar parallax. Through the angle of this parallax, astronomers can work out a star’s distance from Earth.&lt;/p&gt;
  1230.  
  1231. &lt;p&gt;The Danish researcher Ejnar Hertzsprung used stellar parallax to obtain the distances to a handful of nearby Cepheid stars, helping calibrate Leavitt’s work. &lt;/p&gt;
  1232.  
  1233. &lt;p&gt;The New York Times article emphasised the “great” telescopes at the &lt;a href="https://www.mtwilson.edu/"&gt;Mount Wilson Observatory&lt;/a&gt; near Los Angeles, where Hubble was working. Telescope size is generally assessed by the diameter of the primary mirror. With a 100-inch (2.5-metre) diameter mirror for collecting light, the Hooker telescope at Mount Wilson was the largest telescope at the time.&lt;/p&gt;
  1234.  
  1235.  
  1236.  
  1237. &lt;p&gt;Large telescopes are not only more sensitive to resolving galaxies, but also create sharper images. Edwin Hubble was therefore well placed to make his discovery. When Hubble compared his photographic plates taken using the 100 inch telescope with those taken on previous nights by other astronomers, he was thrilled to see one bright star appear to change in brightness over time, as expected for a Cepheid. &lt;/p&gt;
  1238.  
  1239. &lt;p&gt;Using Leavitt’s calculations, Hubble found that the distance to his Cepheid exceeded Shapley’s size for the Milky Way. Over subsequent months, Hubble examined other spiral nebulae as he searched for more Cepheids with which to measure distances. Word of Hubble’s observations was spreading among astronomers. At Harvard, Shapley received a letter from Hubble detailing the discovery. He handed it to fellow astronomer Cecilia Payne-Gaposchkin, remarking: &lt;a href="https://hubblesite.org/contents/media/images/2011/15/2847-Image.html"&gt;“Here is the letter that has destroyed my universe”&lt;/a&gt;.&lt;/p&gt;
  1240.  
  1241. &lt;h2&gt;Expansion of the Universe&lt;/h2&gt;
  1242.  
  1243. &lt;p&gt;Besides estimating the distance to a galaxy, telescopes can also measure the speed at which a galaxy moves towards or away from Earth. In order to do this, astronomers measure a galaxy’s spectrum: the different wavelengths of light coming from it. They also calculate an effect known as the &lt;a href="https://www.grc.nasa.gov/www/k-12/airplane/doppler.html"&gt;Doppler shift&lt;/a&gt; and apply it to that spectrum.&lt;/p&gt;
  1244.  
  1245. &lt;p&gt;The Doppler shift occurs for both light and sound waves; it is responsible for the pitch of a siren increasing as an emergency vehicle approaches, then decreasing as it passes you. When a galaxy is moving away from Earth, features of the spectrum known as absorption lines have longer measured wavelengths than they would if they were not moving. This is due to the Doppler shift, and we say that these galaxies have been “redshifted”. &lt;/p&gt;
  1246.  
  1247.  
  1248.  
  1249. &lt;p&gt;Beginning in 1904, the American astronomer Vesto Slipher used the Doppler technique with a 24-inch telescope at the &lt;a href="https://lowell.edu/"&gt;Lowell Observatory&lt;/a&gt; in Flagstaff, Arizona. He found that nebulae &lt;a href="http://www2.lowell.edu/workshops/slipher/"&gt;were either redshifted&lt;/a&gt; (moving away) or blueshifted (travelling towards us). Slipher found that some nebulae were moving away from Earth at speeds as high as a thousand kilometres a second. &lt;/p&gt;
  1250.  
  1251. &lt;p&gt;Hubble combined Slipher’s measurements with his distance estimates for each galaxy and discovered a relationship: the further a galaxy is from us, the faster it is moving away from us. This can be explained by the expansion of the Universe from a common origin, which would become known derisively as &lt;a href="https://theconversation.com/it-all-started-with-a-big-bang-the-quest-to-unravel-the-mystery-behind-the-birth-of-the-universe-239911"&gt;the Big Bang&lt;/a&gt;.&lt;/p&gt;
  1252.  
  1253. &lt;p&gt;The announcement 100 years ago cemented Hubble’s place in the history of astronomy. His name would later be used for one of the most powerful scientific instruments ever created: the &lt;a href="https://hubblesite.org/home"&gt;Hubble space telescope&lt;/a&gt;. It seems incredible how, over the course of just five years, our understanding of the Universe was brought into focus.&lt;/p&gt;&lt;img src="https://counter.theconversation.com/content/242952/count.gif" alt="The Conversation" width="1" height="1" /&gt;
  1254. &lt;p class="fine-print"&gt;&lt;em&gt;&lt;span&gt;Jeffrey Grube does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.&lt;/span&gt;&lt;/em&gt;&lt;/p&gt;</content>
  1255.    <summary>In 1924, astronomer Edwin Hubble realised two objects were too distant to be inside our galaxy.</summary>
  1256.    <author>
  1257.      <name>Jeffrey Grube, Senior Lecturer in Physics Education, King's College London</name>
  1258.      <foaf:homepage rdf:resource="https://theconversation.com/profiles/jeffrey-grube-2261366"/>
  1259.    </author>
  1260.    <rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
  1261.  </entry>
  1262.  <entry>
  1263.    <id>tag:theconversation.com,2011:article/236699</id>
  1264.    <published>2024-11-14T19:22:04Z</published>
  1265.    <updated>2024-11-14T19:22:04Z</updated>
  1266.    <link rel="alternate" type="text/html" href="https://theconversation.com/egg-shaped-galaxies-may-be-aligned-to-the-black-holes-at-their-hearts-astronomers-find-236699"/>
  1267.    <title>Egg-shaped galaxies may be aligned to the black holes at their hearts, astronomers find</title>
  1268.    <content type="html">&lt;figure&gt;&lt;img src="https://images.theconversation.com/files/631297/original/file-20241111-15-3hrrqd.jpg?ixlib=rb-4.1.0&amp;amp;rect=21%2C706%2C2782%2C1593&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=496&amp;amp;fit=clip" /&gt;&lt;figcaption&gt;&lt;span class="caption"&gt;The active galaxy Centaurus A, with jets emanating from the central black hole.&lt;/span&gt; &lt;span class="attribution"&gt;&lt;a class="source" href="https://www.eso.org/public/images/eso0903a/"&gt;ESO/WFI (Optical); MPIfR/ESO/APEX/A.Weiss et al. (Submillimetre); NASA/CXC/CfA/R.Kraft et al. (X-ray)&lt;/a&gt;, &lt;a class="license" href="http://creativecommons.org/licenses/by/4.0/"&gt;CC BY&lt;/a&gt;&lt;/span&gt;&lt;/figcaption&gt;&lt;/figure&gt;&lt;p&gt;Black holes don’t have many identifying features. They come in one colour (black) and one shape (spherical). &lt;/p&gt;
  1269.  
  1270. &lt;p&gt;The main difference between black holes is mass: some weigh about as much as a star like our Sun, while others weigh around a million times more. Stellar-mass black holes can be found anywhere in a galaxy, but the really big ones (known as supermassive black holes) are found in the cores of galaxies.&lt;/p&gt;
  1271.  
  1272. &lt;p&gt;These supermassive behemoths are still quite tiny when seen in cosmic perspective, typically containing only around 1% of their host galaxy’s mass and extending only to a millionth of its width.  &lt;/p&gt;
  1273.  
  1274. &lt;p&gt;However, as we have just discovered, there is a surprising link between what goes on near the black hole and the shape of the entire galaxy that surrounds it. Our results are published in &lt;a href="https://www.nature.com/articles/s41550-024-02407-4"&gt;Nature Astronomy&lt;/a&gt;.&lt;/p&gt;
  1275.  
  1276. &lt;h2&gt;When black holes light up&lt;/h2&gt;
  1277.  
  1278. &lt;p&gt;Supermassive black holes are fairly rare. Our Milky Way galaxy has one at its centre (named &lt;a href="https://theconversation.com/say-hello-to-sagittarius-a-the-black-hole-at-the-center-of-the-milky-way-galaxy-183008"&gt;Sagittarius A*&lt;/a&gt;), and many other galaxies also seem to host a single supermassive black hole at their core. &lt;/p&gt;
  1279.  
  1280. &lt;p&gt;Under the right circumstances, dust and gas falling into these galactic cores can form a disk of hot material around the black hole. This “accretion disk” in turn generates a super-heated jet of charged particles that are ejected from the black hole at mind-boggling velocities, close to the speed of light. &lt;/p&gt;
  1281.  
  1282. &lt;p&gt;When a supermassive black hole lights up like this, we call it a quasar. &lt;/p&gt;
  1283.  
  1284. &lt;h2&gt;How to watch a quasar&lt;/h2&gt;
  1285.  
  1286. &lt;p&gt;To get a good look at quasar jets, astronomers often use radio telescopes. In fact, we sometimes combine observations from multiple radio telescopes located in different parts of the world.&lt;/p&gt;
  1287.  
  1288. &lt;p&gt;Using a technique called very long baseline interferometry, we can in effect make a single telescope the size of the entire Earth. This massive eye is much better at resolving fine detail than any individual telescope. &lt;/p&gt;
  1289.  
  1290. &lt;p&gt;As a result, we can not only see objects and structures much smaller than we can with the naked eye, we can do better than the James Webb Space Telescope. &lt;/p&gt;
  1291.  
  1292. &lt;figure class="align-center zoomable"&gt;
  1293.            &lt;a href="https://images.theconversation.com/files/631978/original/file-20241114-15-xsithi.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=1000&amp;amp;fit=clip"&gt;&lt;img alt="Image showing an elliptical galaxy with zoomed in sections of the black hole and jet at its centre." src="https://images.theconversation.com/files/631978/original/file-20241114-15-xsithi.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;fit=clip" srcset="https://images.theconversation.com/files/631978/original/file-20241114-15-xsithi.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=450&amp;amp;fit=crop&amp;amp;dpr=1 600w, https://images.theconversation.com/files/631978/original/file-20241114-15-xsithi.png?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=450&amp;amp;fit=crop&amp;amp;dpr=2 1200w, https://images.theconversation.com/files/631978/original/file-20241114-15-xsithi.png?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=450&amp;amp;fit=crop&amp;amp;dpr=3 1800w, https://images.theconversation.com/files/631978/original/file-20241114-15-xsithi.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=566&amp;amp;fit=crop&amp;amp;dpr=1 754w, https://images.theconversation.com/files/631978/original/file-20241114-15-xsithi.png?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=566&amp;amp;fit=crop&amp;amp;dpr=2 1508w, https://images.theconversation.com/files/631978/original/file-20241114-15-xsithi.png?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=566&amp;amp;fit=crop&amp;amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"&gt;&lt;/a&gt;
  1294.            &lt;figcaption&gt;
  1295.              &lt;span class="caption"&gt;Black holes are millions of times smaller than galaxies, yet make jets that are pointed in the same direction as the entire galaxy. Optical image: NASA, ESA, R.M. Crockett (University of Oxford, U.K.), S. Kaviraj (Imperial College London and University of Oxford, U.K.), J. Silk (University of Oxford), M. Mutchler (Space Telescope Science Institute, Baltimore, USA), R. O'Connell (University of Virginia, Charlottesville, USA), and the WFC3 Scientific Oversight Committee. Top right: MOJAVE Collaboration, NRAO/NSF. Bottom right: Event Horizon Telescope / ESO (same as before)&lt;/span&gt;
  1296.              &lt;span class="attribution"&gt;&lt;a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/"&gt;CC BY-SA&lt;/a&gt;&lt;/span&gt;
  1297.            &lt;/figcaption&gt;
  1298.          &lt;/figure&gt;
  1299.  
  1300. &lt;p&gt;This is the technique that was used to make the first “&lt;a href="https://theconversation.com/a-unique-collaboration-using-a-virtual-earth-sized-telescope-shows-how-science-is-changing-in-the-21st-century-201556"&gt;black hole image&lt;/a&gt;” in 2019, showing the halo of light generated around the supermassive black hole hosted by the galaxy M87.&lt;/p&gt;
  1301.  
  1302. &lt;p&gt;Quasar jets that can be detected using very long baseline interferometry can be millions of light years long and are almost always found in elliptical galaxies. Using very long baseline interferometry, we can observe them all the way down to a few light years or so from their black hole of origin.&lt;/p&gt;
  1303.  
  1304. &lt;p&gt;The direction of the jet near its source tells us about the orientation of the accretion disk, and so potentially the properties of the black hole itself.&lt;/p&gt;
  1305.  
  1306. &lt;h2&gt;Connection to the host galaxy&lt;/h2&gt;
  1307.  
  1308. &lt;p&gt;What about the host galaxies? A galaxy is a three-dimensional object, formed of hundreds of billions of stars. &lt;/p&gt;
  1309.  
  1310. &lt;p&gt;But it appears to us (observed in optical or infrared) in projection, either as an ellipse or a spiral. We can measure the shape of these galaxies, tracing the profile of starlight, and measure the long axis and short axis of the two-dimensional shape. &lt;/p&gt;
  1311.  
  1312. &lt;p&gt;In our paper, we compared the direction of quasar jets with the direction of this shorter axis of the galaxy ellipse, and found that they tend to be pointing in the same direction. This alignment is more statistically significant than you would expect if they were both randomly oriented.&lt;/p&gt;
  1313.  
  1314. &lt;p&gt;This is surprising, as the black hole is so small (the jets we measure are only a few light years in length) compared to the host galaxy (which can be hundreds of thousands or even millions of light years across).&lt;/p&gt;
  1315.  
  1316. &lt;p&gt;It is surprising that such a relatively small object can affect, or be affected by, the environment on such large scales. We might expect to see a correlation between the jet and the local environment, but not with the whole galaxy.&lt;/p&gt;
  1317.  
  1318. &lt;h2&gt;How galaxies form&lt;/h2&gt;
  1319.  
  1320. &lt;p&gt;Does this have something to say about the way galaxies form? &lt;/p&gt;
  1321.  
  1322. &lt;p&gt;Spiral galaxies are perhaps the most famous kind of galaxy, but sometimes they collide with other spirals and form elliptical galaxies. We see these three-dimensional egg-shaped blobs as two-dimensional ellipses on the sky. &lt;/p&gt;
  1323.  
  1324. &lt;p&gt;The merger process triggers quasar activity in ways we don’t fully understand. As a result, almost all quasar jets that can be detected using very long baseline interferometry are hosted in elliptical galaxies.&lt;/p&gt;
  1325.  
  1326. &lt;p&gt;The exact interpretation of our results remains mysterious, but is important in the context of the &lt;a href="https://theconversation.com/the-earliest-galaxies-formed-amazingly-fast-after-the-big-bang-do-they-break-the-universe-or-change-its-age-237416"&gt;recent James Webb Space Telescope discovery&lt;/a&gt; of highly massive quasars (with massive black holes), which have formed much earlier in the universe than expected. Clearly, our understanding of how galaxies form and how black holes influence that needs to be updated.&lt;/p&gt;&lt;img src="https://counter.theconversation.com/content/236699/count.gif" alt="The Conversation" width="1" height="1" /&gt;
  1327. &lt;p class="fine-print"&gt;&lt;em&gt;&lt;span&gt;David Parkinson receives funding from the Korea Astronomy and Space Science Institute. &lt;/span&gt;&lt;/em&gt;&lt;/p&gt;&lt;p class="fine-print"&gt;&lt;em&gt;&lt;span&gt;Jeffrey Hodgson receives funding from the National Research Foundation of Korea. &lt;/span&gt;&lt;/em&gt;&lt;/p&gt;</content>
  1328.    <summary>New analysis of radio telescope data links the shape of galaxies to the supermassive black holes they host.</summary>
  1329.    <author>
  1330.      <name>David Parkinson, Research Scientist in Astrophysics, The University of Queensland</name>
  1331.      <foaf:homepage rdf:resource="https://theconversation.com/profiles/david-parkinson-126017"/>
  1332.    </author>
  1333.    <author>
  1334.      <name>Jeffrey Hodgson, Assistant Professor in Astrophysics, Sejong University</name>
  1335.      <foaf:homepage rdf:resource="https://theconversation.com/profiles/jeffrey-hodgson-2203966"/>
  1336.    </author>
  1337.    <rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
  1338.  </entry>
  1339.  <entry>
  1340.    <id>tag:theconversation.com,2011:article/243200</id>
  1341.    <published>2024-11-11T12:56:46Z</published>
  1342.    <updated>2024-11-11T12:56:46Z</updated>
  1343.    <link rel="alternate" type="text/html" href="https://theconversation.com/a-distant-planet-seems-to-have-a-sulphur-rich-atmosphere-hinting-at-alien-volcanoes-243200"/>
  1344.    <title>A distant planet seems to have a sulphur-rich atmosphere, hinting at alien volcanoes</title>
  1345.    <content type="html">&lt;p&gt;Today, we know of more than &lt;a href="https://exoplanetarchive.ipac.caltech.edu/index.html"&gt;5,000 exoplanets&lt;/a&gt;: planets outside our solar system that orbit other stars. While the effort to discover new worlds goes on, we’re steadily learning more about the exoplanets we’ve already detected: their sizes, what they’re made of and whether they have atmospheres.&lt;/p&gt;
  1346.  
  1347. &lt;p&gt;Our team has now provided tentative evidence for a sulphur-rich atmosphere on a world that’s 1.5 times the size of Earth and located 35 light years away. If confirmed, it would be the smallest known exoplanet with an atmosphere. The potential presence of the gases &lt;a href="https://www.britannica.com/science/sulfur-dioxide"&gt;sulphur dioxide (SO₂)&lt;/a&gt; and &lt;a href="https://www.britannica.com/science/hydrogen-sulfide"&gt;hydrogen sulphide (H₂S)&lt;/a&gt; in this atmosphere hint at a molten or volcanic surface.&lt;/p&gt;
  1348.  
  1349. &lt;p&gt;In our solar system, we have two distinct categories of planets – the small rocky
  1350. ones, including Earth and Mars, and the gas giants such as Jupiter and Saturn. However, exoplanets span a great spectrum of sizes. Our solar system lacks a planet whose size falls into the range between Earth and Neptune, but it turns out that’s the most common type of planet we have seen around other stars in our galaxy. &lt;/p&gt;
  1351.  
  1352. &lt;p&gt;The ones closer to Neptune’s size are called &lt;a href="https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2020JE006639"&gt;sub-Neptunes&lt;/a&gt; and the ones closer to Earth’s size are called &lt;a href="https://science.nasa.gov/exoplanets/super-earth/"&gt;super-Earths&lt;/a&gt;. L 98-59 d is a super-Earth, slightly bigger and heavier than the Earth. The composition of the atmospheres of these planets is still an open question, one that we are only starting to explore with the James Webb Space Telescope (JWST), launched in 2021.&lt;/p&gt;
  1353.  
  1354. &lt;p&gt;L 98-59 d was &lt;a href="https://iopscience.iop.org/article/10.3847/1538-3881/ab2459"&gt;discovered in 2019&lt;/a&gt; with Nasa’s &lt;a href="https://science.nasa.gov/mission/tess/"&gt;Tess space telescope&lt;/a&gt;. Most exoplanets, including L 98-59 d, have been detected using the &lt;a href="https://science.nasa.gov/mission/roman-space-telescope/transit-method/"&gt;“transit method”&lt;/a&gt;. This measures the tiny dips in starlight when the planet passes in front of the star. This dip is more pronounced for larger planets and enables us to figure out the size of a planet.&lt;/p&gt;
  1355.  
  1356. &lt;p&gt;Even JWST can’t separate these tiny planets from their host stars – as they orbit their stars too closely. But there is a way to “see” the planet’s atmosphere from this entangled light. When a planet passes in front of its star, some of the starlight filters through a planet’s atmosphere, hitting the gas molecules or atoms present there, on its way to us on Earth. &lt;/p&gt;
  1357.  
  1358. &lt;p&gt;Every gas modifies the light in its own signature manner. From the light we receive from that star system, we can infer what the composition of that atmosphere might be. This is called &lt;a href="https://science.nasa.gov/resource/a-planets-transmission-spectrum/"&gt;transmission spectroscopy&lt;/a&gt;, a proven technique that has previously been used to confirm the &lt;a href="https://theconversation.com/james-webb-space-telescope-uncovers-chemical-secret%20s-of-distant-world-paving-the-way-for-studying-earth-like-planets-195224"&gt;presence of CO₂&lt;/a&gt; in an exoplanet’s atmosphere.&lt;/p&gt;
  1359.  
  1360. &lt;figure class="align-center "&gt;
  1361.            &lt;img alt="Active vents erupt lava in Halemaʻumaʻu crater at the summit of Kīlauea volcano, Hawaii." src="https://images.theconversation.com/files/630702/original/file-20241107-15-xa58gp.jpeg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;fit=clip" srcset="https://images.theconversation.com/files/630702/original/file-20241107-15-xa58gp.jpeg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=450&amp;amp;fit=crop&amp;amp;dpr=1 600w, https://images.theconversation.com/files/630702/original/file-20241107-15-xa58gp.jpeg?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=450&amp;amp;fit=crop&amp;amp;dpr=2 1200w, https://images.theconversation.com/files/630702/original/file-20241107-15-xa58gp.jpeg?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=450&amp;amp;fit=crop&amp;amp;dpr=3 1800w, https://images.theconversation.com/files/630702/original/file-20241107-15-xa58gp.jpeg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=566&amp;amp;fit=crop&amp;amp;dpr=1 754w, https://images.theconversation.com/files/630702/original/file-20241107-15-xa58gp.jpeg?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=566&amp;amp;fit=crop&amp;amp;dpr=2 1508w, https://images.theconversation.com/files/630702/original/file-20241107-15-xa58gp.jpeg?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=566&amp;amp;fit=crop&amp;amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"&gt;
  1362.            &lt;figcaption&gt;
  1363.              &lt;span class="caption"&gt;The potential detection of sulphur dioxide and hydrogen sulphide hint at a molten or volcanic surface.&lt;/span&gt;
  1364.              &lt;span class="attribution"&gt;&lt;a class="source" href="https://npgallery.nps.gov/AssetDetail/67cd8153-f04a-43c9-a673-b18282d03736"&gt;USGS Photo&lt;/a&gt;&lt;/span&gt;
  1365.            &lt;/figcaption&gt;
  1366.          &lt;/figure&gt;
  1367.  
  1368. &lt;p&gt;I am part of an international team of scientists who used JWST to observe one
  1369. transit of L 98-59 d across the disc of its host star. We then obtained the transmission spectrum of the &lt;a href="https://iopscience.iop.org/article/10.3847/2041-8213/ad73d1"&gt;atmosphere of the exoplanet&lt;/a&gt; from these observations. This spectrum hinted at the possible presence of an &lt;a href="https://iopscience.iop.org/article/10.3847/2041-8213/ad73d0"&gt;atmosphere filled with sulphur dioxide and hydrogen sulphide&lt;/a&gt;. &lt;/p&gt;
  1370.  
  1371. &lt;p&gt;This discovery was surprising, as it stands out in stark contrast to the atmospheres of rocky planets in our own solar system, where water vapour and carbon dioxide are much more prevalent. Earth’s atmosphere, for example, is rich in nitrogen and oxygen, with trace amounts of water vapour. Meanwhile, Venus has &lt;a href="https://science.nasa.gov/venus/venus-facts/"&gt;a thick atmosphere&lt;/a&gt; dominated by carbon dioxide. Even &lt;a href="https://marsed.asu.edu/mep/atmosphere"&gt;Mars has a thin atmosphere&lt;/a&gt; dominated by carbon dioxide.&lt;/p&gt;
  1372.  
  1373. &lt;p&gt;We then used computer models that incorporate our understanding of planetary atmospheres and the light coming from L 98-59 d to come up with a potential picture of the composition of this planet’s atmosphere. The absence of common gases such as carbon dioxide and the presence of SO₂ and H₂S suggests an atmosphere shaped by entirely different processes to those we’re familiar with in our solar system. This hints at unique and extreme conditions on L 98-59 d, such as a molten or volcanic surface.&lt;/p&gt;
  1374.  
  1375. &lt;p&gt;Additional observations will be necessary to confirm the presence of these gases. JWST observations had previously spotted &lt;a href="https://theconversation.com/james-webb-space-telescope-uncovers-chemical-secret%20s-of-distant-world-paving-the-way-for-studying-earth-like-planets-195224"&gt;signs of SO₂&lt;/a&gt; on an exoplanet, but this was a gas giant, not a potentially rocky world such as L 98-59 d.&lt;/p&gt;
  1376.  
  1377.  
  1378.  
  1379. &lt;h2&gt;Exo-volcanoes?&lt;/h2&gt;
  1380.  
  1381. &lt;p&gt;The potential presence of SO₂ and H₂S raises questions about their origin. One explosive possibility is volcanism driven by &lt;a href="https://www.esi.utexas.edu/files/078-Learning-Module-What-is-Tidal-Heating.pdf"&gt;tidal heating&lt;/a&gt;, much like what is observed on &lt;a href="https://theconversation.com/jupiters-moon-overflowing-with-volcanos-5946"&gt;Jupiter’s moon Io&lt;/a&gt;. The gravitational pull of the host star on this planet stretches and squeezes it as it goes along its orbit. This motion can heat up the centre of the planet, melting its interiors and producing extreme volcanic eruptions and possibly even oceans of magma.&lt;/p&gt;
  1382.  
  1383. &lt;p&gt;Combined with its close proximity to the star (one year on this planet is seven and half Earth days), truly hellish temperatures can be reached on the surface.
  1384. If future observations support the presence of such an atmosphere, not only would it be the smallest exoplanet to have a detected atmosphere, but also a crucial step towards understanding the nature of such planets. &lt;/p&gt;
  1385.  
  1386. &lt;p&gt;Detecting atmospheres on small, rocky planets is exceptionally difficult, as the planets are very small compared to the host stars, and also as intense radiation from their host stars often strips the atmospheres away. These observations, while tantalising, are only from a single transit. That means instrumental noise and other factors prevent us from making statistically strong claims. Future JWST observations will be key in confirming or refuting our analysis.&lt;/p&gt;
  1387.  
  1388. &lt;p&gt;L 98-59 d may not be a candidate for life as we know it, but studying its sulphurous atmosphere and potential volcanism provides valuable insight into worlds around other stars. Extreme worlds like these help us understand the diversity of planetary evolution across the galaxy.&lt;/p&gt;&lt;img src="https://counter.theconversation.com/content/243200/count.gif" alt="The Conversation" width="1" height="1" /&gt;
  1389. &lt;p class="fine-print"&gt;&lt;em&gt;&lt;span&gt;Agnibha Banerjee receives funding from the Science and Technology Facilities Council and The Open University. &lt;/span&gt;&lt;/em&gt;&lt;/p&gt;</content>
  1390.    <summary>Astronomers have detected possible signs of gases released by volcanic activity.</summary>
  1391.    <author>
  1392.      <name>Agnibha Banerjee, PhD Student, The Open University</name>
  1393.      <foaf:homepage rdf:resource="https://theconversation.com/profiles/agnibha-banerjee-2246487"/>
  1394.    </author>
  1395.    <rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
  1396.  </entry>
  1397.  <entry>
  1398.    <id>tag:theconversation.com,2011:article/240885</id>
  1399.    <published>2024-11-05T13:44:11Z</published>
  1400.    <updated>2024-11-05T13:44:11Z</updated>
  1401.    <link rel="alternate" type="text/html" href="https://theconversation.com/carl-sagans-scientific-legacy-extends-far-beyond-cosmos-240885"/>
  1402.    <title>Carl Sagan’s scientific legacy extends far beyond ‘Cosmos’</title>
  1403.    <content type="html">&lt;figure&gt;&lt;img src="https://images.theconversation.com/files/627532/original/file-20241023-17-muc6em.jpg?ixlib=rb-4.1.0&amp;amp;rect=7%2C0%2C4678%2C3105&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=496&amp;amp;fit=clip" /&gt;&lt;figcaption&gt;&lt;span class="caption"&gt;Carl Sagan at his Cornell University laboratory in Ithaca, N.Y., in 1974.&lt;/span&gt; &lt;span class="attribution"&gt;&lt;a class="source" href="https://www.gettyimages.com/detail/news-photo/portrait-of-american-astronomer-and-author-carl-sagan-news-photo/3232391?adppopup=true"&gt;Santi Visalli, Inc./Archive Photos via Getty Images&lt;/a&gt;&lt;/span&gt;&lt;/figcaption&gt;&lt;/figure&gt;&lt;p&gt;On Nov. 9, 2024, the world will mark Carl Sagan’s 90th birthday – but sadly without Sagan, who &lt;a href="https://www.nytimes.com/1996/12/21/us/carl-sagan-an-astronomer-who-excelled-at-popularizing-science-is-dead-at-62.html"&gt;died in 1996 at the age of 62&lt;/a&gt;. &lt;/p&gt;
  1404.  
  1405. &lt;p&gt;Most people remember him as the co-creator and host of the 1980 &lt;a href="https://www.imdb.com/title/tt0081846/"&gt;“Cosmos” television series&lt;/a&gt;, watched worldwide by hundreds of millions of people. Others read “&lt;a href="https://www.simonandschuster.com/books/Contact/Carl-Sagan/9781501197987#:%7E"&gt;Contact&lt;/a&gt;,” his best-selling science fiction novel, or “&lt;a href="https://www.penguinrandomhouse.com/books/159732/dragons-of-eden-by-carl-sagan/"&gt;The Dragons of Eden&lt;/a&gt;,” his Pulitzer Prize-winning nonfiction book. Millions more saw him popularize astronomy on “&lt;a href="https://www.youtube.com/watch?v=cPM5WpS65tk"&gt;The Tonight Show&lt;/a&gt;.” &lt;/p&gt;
  1406.  
  1407. &lt;p&gt;What most people don’t know about Sagan, and what has been somewhat obscured by his fame, is the far-reaching impact of his science, which resonates to this day. Sagan was an unequaled science communicator, astute advocate and prolific writer. But he was also an outstanding scientist. &lt;/p&gt;
  1408.  
  1409. &lt;p&gt;Sagan propelled science forward in at least three important ways. He produced notable results and insights described in over 600 scientific papers. He enabled new scientific disciplines to flourish. And he inspired multiple generations of scientists. &lt;a href="https://seti.ucla.edu/jlm/"&gt;As a planetary astronomer&lt;/a&gt;, I believe such a combination of talents and accomplishments is rare and may occur only once in my lifetime. &lt;/p&gt;
  1410.  
  1411. &lt;h2&gt;Scientific accomplishments&lt;/h2&gt;
  1412.  
  1413. &lt;p&gt;Very little was known in the 1960s about &lt;a href="https://science.nasa.gov/venus/"&gt;Venus&lt;/a&gt;. Sagan investigated how the greenhouse effect in its carbon dioxide atmosphere might explain the unbearably high temperature on Venus – approximately 870 degrees Fahrenheit (465 degrees Celsius). His research remains a cautionary tale about the &lt;a href="https://www.unep.org/topics/climate-action"&gt;dangers of fossil fuel emissions&lt;/a&gt; here on Earth. &lt;/p&gt;
  1414.  
  1415. &lt;figure class="align-right zoomable"&gt;
  1416.            &lt;a href="https://images.theconversation.com/files/628581/original/file-20241028-15-e0frff.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=1000&amp;amp;fit=clip"&gt;&lt;img alt="Carl Sagan poses before a backdrop that shows the stars and galaxies of space." src="https://images.theconversation.com/files/628581/original/file-20241028-15-e0frff.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=237&amp;amp;fit=clip" srcset="https://images.theconversation.com/files/628581/original/file-20241028-15-e0frff.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=680&amp;amp;fit=crop&amp;amp;dpr=1 600w, https://images.theconversation.com/files/628581/original/file-20241028-15-e0frff.jpg?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=680&amp;amp;fit=crop&amp;amp;dpr=2 1200w, https://images.theconversation.com/files/628581/original/file-20241028-15-e0frff.jpg?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=680&amp;amp;fit=crop&amp;amp;dpr=3 1800w, https://images.theconversation.com/files/628581/original/file-20241028-15-e0frff.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=855&amp;amp;fit=crop&amp;amp;dpr=1 754w, https://images.theconversation.com/files/628581/original/file-20241028-15-e0frff.jpg?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=855&amp;amp;fit=crop&amp;amp;dpr=2 1508w, https://images.theconversation.com/files/628581/original/file-20241028-15-e0frff.jpg?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=855&amp;amp;fit=crop&amp;amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"&gt;&lt;/a&gt;
  1417.            &lt;figcaption&gt;
  1418.              &lt;span class="caption"&gt;Carl Sagan hosted and co-wrote ‘Cosmos,’ a 13-part TV series that aired on PBS stations from 1980 to 1981.&lt;/span&gt;
  1419.              &lt;span class="attribution"&gt;&lt;a class="source" href="https://www.gettyimages.com/detail/news-photo/astrophysicist-carl-sagan-poses-before-a-florida-state-news-photo/99281051?adppopup=true"&gt;Mickey Adair/Michael Ochs Archives/Hulton Archive via Getty Images&lt;/a&gt;&lt;/span&gt;
  1420.            &lt;/figcaption&gt;
  1421.          &lt;/figure&gt;
  1422.  
  1423. &lt;p&gt;Sagan proposed a compelling explanation for seasonal changes in the brightness of Mars, which had been incorrectly attributed to vegetation or volcanic activity. Wind-blown dust was &lt;a href="https://science.nasa.gov/blog/everything-is-dust-in-the-wind/"&gt;responsible for the mysterious variations&lt;/a&gt;, he explained.&lt;/p&gt;
  1424.  
  1425. &lt;p&gt;Sagan and his students studied how changes to the reflectivity of Earth’s surface and atmosphere affect our climate. They considered how the detonation of nuclear bombs could inject so much soot into the atmosphere that it would lead to a yearslong period of substantial cooling, a phenomenon &lt;a href="https://www.smithsonianmag.com/science-nature/when-carl-sagan-warned-world-about-nuclear-winter-180967198/"&gt;known as nuclear winter&lt;/a&gt;. &lt;/p&gt;
  1426.  
  1427. &lt;p&gt;With unusual breadth in astronomy, physics, chemistry and biology, Sagan pushed forward the nascent discipline of astrobiology – the study of life in the universe.&lt;br&gt;
  1428. Together with the research scientist &lt;a href="https://www.seti.org/bishun-khare"&gt;Bishun Khare&lt;/a&gt; at Cornell University, Sagan conducted pioneering laboratory experiments and showed that certain ingredients of prebiotic chemistry, called &lt;a href="https://www.planetary.org/articles/0722-what-in-the-worlds-are-tholins"&gt;tholins&lt;/a&gt;, and certain building blocks of life, known as &lt;a href="https://www.smithsonianmag.com/smart-news/building-blocks-of-life-found-on-samples-collected-from-an-asteroid-180980231/"&gt;amino acids&lt;/a&gt;, form naturally in laboratory environments that mimic planetary settings. &lt;/p&gt;
  1429.  
  1430. &lt;figure class="align-left zoomable"&gt;
  1431.            &lt;a href="https://images.theconversation.com/files/628602/original/file-20241028-17-z9w8qx.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=1000&amp;amp;fit=clip"&gt;&lt;img alt="A photograph of the golden record." src="https://images.theconversation.com/files/628602/original/file-20241028-17-z9w8qx.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=237&amp;amp;fit=clip" srcset="https://images.theconversation.com/files/628602/original/file-20241028-17-z9w8qx.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=600&amp;amp;fit=crop&amp;amp;dpr=1 600w, https://images.theconversation.com/files/628602/original/file-20241028-17-z9w8qx.jpg?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=600&amp;amp;fit=crop&amp;amp;dpr=2 1200w, https://images.theconversation.com/files/628602/original/file-20241028-17-z9w8qx.jpg?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=600&amp;amp;fit=crop&amp;amp;dpr=3 1800w, https://images.theconversation.com/files/628602/original/file-20241028-17-z9w8qx.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=754&amp;amp;fit=crop&amp;amp;dpr=1 754w, https://images.theconversation.com/files/628602/original/file-20241028-17-z9w8qx.jpg?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=754&amp;amp;fit=crop&amp;amp;dpr=2 1508w, https://images.theconversation.com/files/628602/original/file-20241028-17-z9w8qx.jpg?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=754&amp;amp;fit=crop&amp;amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"&gt;&lt;/a&gt;
  1432.            &lt;figcaption&gt;
  1433.              &lt;span class="caption"&gt;Carl Sagan proposed the ‘Golden Record,’ which features the sounds of Earth, including greetings spoken in 55 languages.&lt;/span&gt;
  1434.              &lt;span class="attribution"&gt;&lt;a class="source" href="https://commons.wikimedia.org/wiki/File:The_Sounds_of_Earth_-_GPN-2000-001976.jpg"&gt;NASA via Wikimedia Commons&lt;/a&gt;&lt;/span&gt;
  1435.            &lt;/figcaption&gt;
  1436.          &lt;/figure&gt;
  1437.  
  1438. &lt;p&gt;He also modeled the delivery of prebiotic molecules to the early Earth &lt;a href="https://doi.org/10.1126/science.11538074"&gt;by asteroids and comets&lt;/a&gt;, and he was deeply engaged in the biological experiments onboard the &lt;a href="https://science.nasa.gov/mission/viking/"&gt;Mars Viking landers&lt;/a&gt;. Sagan also speculated about the possibility of balloon-shaped organisms floating &lt;a href="https://www.missionjuno.swri.edu/jupiter/atmosphere?show=hs_jupiter_atmosphere_story_is-there-life-on-jupiter"&gt;in the atmospheres of Venus and Jupiter&lt;/a&gt;. &lt;/p&gt;
  1439.  
  1440. &lt;p&gt;His passion for finding life elsewhere extended far beyond the solar system. He was a champion of the search for extraterrestrial intelligence, &lt;a href="https://www.planetary.org/sci-tech/seti"&gt;also known as SETI&lt;/a&gt;. He helped fund and participated in a systematic &lt;a href="https://carlsagan.com/the-search-for-signals-from-space/"&gt;search for extraterrestrial radio beacons&lt;/a&gt; by scanning 70% of the sky with the physicist and electrical engineer &lt;a href="https://www.physics.harvard.edu/people/facpages/horowitz"&gt;Paul Horowitz&lt;/a&gt;. &lt;/p&gt;
  1441.  
  1442. &lt;p&gt;He proposed and co-designed the &lt;a href="https://science.nasa.gov/resource/pioneer-plaque/"&gt;plaques&lt;/a&gt; and &lt;a href="https://science.nasa.gov/mission/voyager/golden-record-contents/greetings/"&gt;the “Golden Records”&lt;/a&gt; now affixed to humanity’s most distant ambassadors, the &lt;a href="https://science.nasa.gov/mission/pioneer-10/"&gt;Pioneer&lt;/a&gt; and &lt;a href="https://science.nasa.gov/mission/voyager/"&gt;Voyager&lt;/a&gt; spacecrafts. It is unlikely that extraterrestrials will ever find these artifacts, but Sagan wanted people to &lt;a href="https://theconversation.com/voyager-golden-records-40-years-later-real-audience-was-always-here-on-earth-79886"&gt;contemplate the possibility of communication&lt;/a&gt; with other civilizations.  &lt;/p&gt;
  1443.  
  1444. &lt;figure&gt;
  1445.            &lt;iframe width="440" height="260" src="https://www.youtube.com/embed/tLPkpBN6bEI?wmode=transparent&amp;amp;start=0" frameborder="0" allowfullscreen=""&gt;&lt;/iframe&gt;
  1446.            &lt;figcaption&gt;&lt;span class="caption"&gt;Carl Sagan, offering his unique commentary in a scene from ‘Cosmos.’&lt;/span&gt;&lt;/figcaption&gt;
  1447.          &lt;/figure&gt;
  1448.  
  1449. &lt;h2&gt;Advocacy&lt;/h2&gt;
  1450.  
  1451. &lt;p&gt;Sagan’s scientific output repeatedly led him to become an eloquent advocate on issues of societal and scientific significance. He testified before Congress about the &lt;a href="https://www.youtube.com/watch?v=Wp-WiNXH6hI"&gt;dangers of climate change&lt;/a&gt;. He was an antinuclear activist and spoke out &lt;a href="https://www.upi.com/Archives/1986/07/31/Dr-Carl-Sagan-astronomer-and-author-argued-Thursday-that/2365523166400/"&gt;against the Strategic Defense Initiative&lt;/a&gt;, also known as “Star Wars.” He urged collaborations and a &lt;a href="https://www.upi.com/Archives/1987/07/20/Sagan-urges-joint-US-Soviet-exploration-of-Mars/8162553752000/"&gt;joint space mission with the Soviet Union&lt;/a&gt;, in an attempt to improve U.S.-Soviet relations. He spoke directly with members of Congress about the search for extraterrestrial intelligence and organized a &lt;a href="https://seti.ucla.edu/jlm/seti/sagan82.pdf"&gt;petition signed by dozens of prominent scientists&lt;/a&gt; urging support for the search. &lt;/p&gt;
  1452.  
  1453.  
  1454.  
  1455. &lt;p&gt;But perhaps his most important gift to society was his promotion of truth-seeking and critical thinking. He encouraged people to muster the humility and discipline to confront their most cherished beliefs – and to rely on evidence to obtain a more accurate view of the world. His most cited book, “&lt;a href="https://www.penguinrandomhouse.com/books/159731/the-demon-haunted-world-by-carl-sagan/"&gt;The Demon-Haunted World: Science as a Candle in the Dark&lt;/a&gt;,” is a precious resource for anyone trying to navigate this age of disinformation. &lt;/p&gt;
  1456.  
  1457. &lt;h2&gt;Impact&lt;/h2&gt;
  1458.  
  1459. &lt;p&gt;A scientist’s impact can sometimes be gauged by the number of times their scholarly work is cited by other scientists. According to &lt;a href="https://scholar.google.com/citations?user=Wd1k3voAAAAJ&amp;amp;hl=en"&gt;Sagan’s Google Scholar page&lt;/a&gt;, his work continues to accumulate more than 1,000 citations per year. &lt;/p&gt;
  1460.  
  1461. &lt;p&gt;Indeed, his current citation rate exceeds that of many members of the &lt;a href="https://www.nasonline.org/membership/"&gt;National Academy of Sciences&lt;/a&gt;, who are “elected by their peers for outstanding contributions to research,” according to the academy’s website, and is “one of the highest honors a scientist can receive.”&lt;/p&gt;
  1462.  
  1463. &lt;p&gt;Sagan was nominated for election into the academy during the 1991-1992 cycle, but his nomination was challenged at the annual meeting; more than one-third of the members voted to keep him out, &lt;a href="https://gizmodo.com/why-was-carl-sagan-blackballed-from-the-national-academ-1700524296"&gt;which doomed his admission&lt;/a&gt;. An observer at that meeting wrote to Sagan, “It is the worst of human frailties that keeps you out: jealousy.” This belief was &lt;a href="https://search.worldcat.org/title/45082265"&gt;affirmed by others in attendance&lt;/a&gt;. In my opinion, the academy’s failure to admit Sagan remains an enduring stain on the organization. &lt;/p&gt;
  1464.  
  1465. &lt;p&gt;No amount of jealousy can diminish Sagan’s profound and wide-ranging legacy. In addition to his scientific accomplishments, Sagan has inspired generations of scientists and brought an appreciation of science to countless nonscientists. He has demonstrated what is possible in the realms of science, communication and advocacy. Those accomplishments required truth-seeking, hard work and self-improvement. On the 90th anniversary of Sagan’s birth, a renewed commitment to these values would honor his memory.&lt;/p&gt;&lt;img src="https://counter.theconversation.com/content/240885/count.gif" alt="The Conversation" width="1" height="1" /&gt;
  1466. &lt;p class="fine-print"&gt;&lt;em&gt;&lt;span&gt;Jean-Luc Margot has received funding from the National Aeronautics and Space Administration, the National Science Foundation, and The Planetary Society, which was co-founded by Carl Sagan. He met Carl Sagan while a graduate student at Cornell University.&lt;/span&gt;&lt;/em&gt;&lt;/p&gt;</content>
  1467.    <summary>On what would’ve been the astronomer’s 90th trip around the Sun, here’s a look at his legacy as a scientist, advocate and communicator.</summary>
  1468.    <author>
  1469.      <name>Jean-Luc Margot, Professor of Earth, Planetary, and Space Sciences, University of California, Los Angeles</name>
  1470.      <foaf:homepage rdf:resource="https://theconversation.com/profiles/jean-luc-margot-1248343"/>
  1471.    </author>
  1472.    <rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
  1473.  </entry>
  1474.  <entry>
  1475.    <id>tag:theconversation.com,2011:article/240078</id>
  1476.    <published>2024-10-17T12:02:45Z</published>
  1477.    <updated>2024-10-17T12:02:45Z</updated>
  1478.    <link rel="alternate" type="text/html" href="https://theconversation.com/a-new-generation-of-telescopes-will-probe-the-unknown-unknowns-that-could-transform-our-knowledge-of-the-universe-240078"/>
  1479.    <title>A new generation of telescopes will probe the ‘unknown unknowns’ that could transform our knowledge of the universe</title>
  1480.    <content type="html">&lt;figure&gt;&lt;img src="https://images.theconversation.com/files/625306/original/file-20241012-15-a3j60e.jpg?ixlib=rb-4.1.0&amp;amp;rect=34%2C13%2C4539%2C3031&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=496&amp;amp;fit=clip" /&gt;&lt;figcaption&gt;&lt;span class="caption"&gt;Illustration of the Extremely Large Telescope, currently under construction in Chile&amp;#39;s Atacama desert.&lt;/span&gt; &lt;span class="attribution"&gt;&lt;a class="source" href="https://www.eso.org/public/images/ELT4k-4-comp-Open/"&gt;ESO&lt;/a&gt;, &lt;a class="license" href="http://creativecommons.org/licenses/by/4.0/"&gt;CC BY&lt;/a&gt;&lt;/span&gt;&lt;/figcaption&gt;&lt;/figure&gt;&lt;p&gt;In recent decades, we’ve learnt huge amounts about the universe and its history. The rapidly developing technology of telescopes – both on Earth and &lt;a href="https://theconversation.com/james-webb-space-telescope-what-astronomers-hope-it-will-reveal-about-the-beginning-of-the-universe-podcast-173436"&gt;in space&lt;/a&gt; – has been a key part of this process, and those that are due to start operating over the next two decades should push the boundaries of our understanding of &lt;a href="https://www.britannica.com/science/cosmology-astronomy/Finite-or-infinite"&gt;cosmology&lt;/a&gt; much further.&lt;/p&gt;
  1481.  
  1482. &lt;p&gt;All observatories have a list of science objectives before they switch on, but it is their unexpected discoveries that can have the biggest impact. Many surprise advances in cosmology were driven by new technology, and the next telescopes have powerful capabilities.&lt;/p&gt;
  1483.  
  1484. &lt;p&gt;Still, there are gaps, such as a lack of upcoming space telescopes for ultraviolet and visible light astronomy. Politics and national interests have slowed scientific progress. Financial belts are tightening at even the most famous observatories.&lt;/p&gt;
  1485.  
  1486. &lt;hr&gt;
  1487.  
  1488.  
  1489.  
  1490. &lt;p&gt;&lt;em&gt;This is article is part of our series Cosmology in crisis? which uncovers the greatest problems facing cosmologists today – and discusses the implications of solving them.&lt;/em&gt;&lt;/p&gt;
  1491.  
  1492. &lt;hr&gt;
  1493.  
  1494. &lt;p&gt;The biggest new telescopes are being built in the &lt;a href="https://astroexploring.com/blog/why-are-telescopes-put-on-mountains-6-big-reasons/"&gt;mountains of Chile&lt;/a&gt;. The &lt;a href="https://elt.eso.org/"&gt;Extremely Large Telescope (ELT)&lt;/a&gt; will house a mirror the size of four tennis courts, under a huge dome in the Atacama desert. &lt;/p&gt;
  1495.  
  1496. &lt;p&gt;Reflecting telescopes like ELT work by using a primary mirror to collect light from the night sky, then reflecting it off other mirrors to a camera. Larger mirrors collect more light and see fainter objects. &lt;/p&gt;
  1497.  
  1498. &lt;figure&gt;
  1499.            &lt;iframe width="440" height="260" src="https://www.youtube.com/embed/ytVC8lBxNaU?wmode=transparent&amp;amp;start=0" frameborder="0" allowfullscreen=""&gt;&lt;/iframe&gt;
  1500.            &lt;figcaption&gt;&lt;span class="caption"&gt;The Extremely Large Telescope under construction atop the Cerro Amazones peak in northern Chile.&lt;/span&gt;&lt;/figcaption&gt;
  1501.          &lt;/figure&gt;
  1502.  
  1503. &lt;p&gt;Another ground-based telescope under construction in Chile is the &lt;a href="https://rubinobservatory.org/"&gt;Vera C. Rubin telescope&lt;/a&gt;. Rubin’s camera is the &lt;a href="https://www.lsst.org/about/camera"&gt;largest ever built&lt;/a&gt;: the &lt;a href="https://new.nsf.gov/news/largest-camera-ever-built-arrives-rubin"&gt;size of a small car&lt;/a&gt; and weighing about three tonnes. Its 3,200 megapixels will photograph the whole sky every three days to spot moving objects. Over the course of 10 years, these photographs will be combined to form a massive time-lapse video of the universe.&lt;/p&gt;
  1504.  
  1505. &lt;p&gt;Astronomy used to be a physically demanding job, requiring travel to remote telescopes in dark sites –- but many astronomers began working from home long before COVID. In the late 20th century, major ground observatories started to put in place technology to allow &lt;a href="https://adsabs.harvard.edu/full/1983IrAJ...16...78E"&gt;astronomers to control telescopes&lt;/a&gt; for observations at night, even when they were not there in person. Remote observing is now commonplace, carried out via the internet.&lt;/p&gt;
  1506.  
  1507.  
  1508.  
  1509. &lt;h2&gt;Expect the unexpected&lt;/h2&gt;
  1510.  
  1511. &lt;p&gt;The view of any telescope on the ground is limited, though, even if it’s on top of a mountain. Launching telescopes into space can get around these limitations.&lt;/p&gt;
  1512.  
  1513. &lt;p&gt;The &lt;a href="https://hubblesite.org/home"&gt;Hubble Space Telescope’s&lt;/a&gt; operational history began when the space shuttle lifted it above the atmosphere on April 25 1990. Hubble got the full &lt;a href="https://science.nasa.gov/mission/hubble/overview/the-history-of-hubble/"&gt;1960s sci-fi treatment&lt;/a&gt;: a rocket to launch it, gyroscopes to point it, and electronic cameras instead of photographic film. But one plan fell through: for Hubble to host a commuting astronaut-astronomer, working decidedly away from home.&lt;/p&gt;
  1514.  
  1515. &lt;p&gt;&lt;a href="https://nap.nationalacademies.org/catalog/12399/scientific-uses-of-the-large-space-telescope"&gt;Hubble was designed&lt;/a&gt; to take a census of the Milky Way and its neighbouring galaxies. Its successor, the &lt;a href="https://www.ucolick.org/%7Egdi/docs/NGST_The_Early_Days_of_JWST.pdf"&gt;James Webb Space Telescope&lt;/a&gt;, would study &lt;a href="https://theconversation.com/the-earliest-galaxies-formed-amazingly-fast-after-the-big-bang-do-they-break-the-universe-or-change-its-age-237416"&gt;even more distant galaxies&lt;/a&gt;.&lt;/p&gt;
  1516.  
  1517. &lt;p&gt;Both telescopes have revolutionised our understanding of the universe, but in ways nobody foresaw. Hubble’s original plans mention none of the discoveries now seen as its &lt;a href="https://www.rmg.co.uk/stories/topics/what-has-hubble-space-telescope-discovered"&gt;greatest hits&lt;/a&gt;: &lt;a href="https://www.nasa.gov/news-release/nasas-hubble-spots-possible-water-plumes-erupting-on-jupiters-moon-europa/"&gt;plumes of water erupting&lt;/a&gt; from Jupiter’s moon Europa, the &lt;a href="https://science.nasa.gov/missions/hubble/hubble-uncovers-black-hole-disk-that-shouldnt-exist/"&gt;vortex around black holes&lt;/a&gt;, invisible &lt;a href="https://www.esa.int/ESA_Multimedia/Images/2007/07/The_Bullet_Cluster2"&gt;dark matter&lt;/a&gt; that &lt;a href="https://esahubble.org/news/heic0701/"&gt;holds the universe together&lt;/a&gt;, and the &lt;a href="https://science.nasa.gov/missions/hubble/nasas-hubble-finds-evidence-for-dark-energy-in-the-young-universe/"&gt;dark energy&lt;/a&gt; that is pulling it apart. &lt;/p&gt;
  1518.  
  1519. &lt;figure class="align-center "&gt;
  1520.            &lt;img alt="The Hubble Space Telescope being deployed from the space shuttle on 25 April 1990." src="https://images.theconversation.com/files/625298/original/file-20241012-15-djgqbo.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;fit=clip" srcset="https://images.theconversation.com/files/625298/original/file-20241012-15-djgqbo.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=359&amp;amp;fit=crop&amp;amp;dpr=1 600w, https://images.theconversation.com/files/625298/original/file-20241012-15-djgqbo.jpg?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=359&amp;amp;fit=crop&amp;amp;dpr=2 1200w, https://images.theconversation.com/files/625298/original/file-20241012-15-djgqbo.jpg?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=359&amp;amp;fit=crop&amp;amp;dpr=3 1800w, https://images.theconversation.com/files/625298/original/file-20241012-15-djgqbo.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=451&amp;amp;fit=crop&amp;amp;dpr=1 754w, https://images.theconversation.com/files/625298/original/file-20241012-15-djgqbo.jpg?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=451&amp;amp;fit=crop&amp;amp;dpr=2 1508w, https://images.theconversation.com/files/625298/original/file-20241012-15-djgqbo.jpg?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=451&amp;amp;fit=crop&amp;amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"&gt;
  1521.            &lt;figcaption&gt;
  1522.              &lt;span class="caption"&gt;The Hubble Space Telescope being deployed from the space shuttle in April 1990.&lt;/span&gt;
  1523.              &lt;span class="attribution"&gt;&lt;a class="source" href="https://www.nasa.gov/solar-system/nasa-returns-hubble-space-telescope-to-science-operations/"&gt;Nasa/Smithsonian Institution/Lockheed Corporation&lt;/a&gt;&lt;/span&gt;
  1524.            &lt;/figcaption&gt;
  1525.          &lt;/figure&gt;
  1526.  
  1527. &lt;p&gt;Webb, launched on December 25 2021,  now spends a &lt;a href="https://www.stsci.edu/contents/newsletters/2024-volume-41-issue-01/the-jwst-cycle-3-go-ar-proposal-review"&gt;third of its time&lt;/a&gt; looking at planets around other stars that weren’t even known about when it was designed.&lt;/p&gt;
  1528.  
  1529. &lt;p&gt;The stated goal of an expensive telescope is usually just a sales pitch to space agencies, governments and (shhh…) taxpayers. The Webb telescope should achieve its &lt;a href="https://science.nasa.gov/mission/webb/science-overview/"&gt;original science goals&lt;/a&gt;, but astronomers have always known that seeing further, finer or in more colours can achieve so much more. The unexpected discoveries by telescopes are often more significant than the science objectives stated at the outset.&lt;/p&gt;
  1530.  
  1531. &lt;h2&gt;Taking the long view&lt;/h2&gt;
  1532.  
  1533. &lt;p&gt;For scientists, it’s a relief that telescopes go beyond their brief, because Hubble and Webb both took more than 25 years from napkin to launch. In that time, new scientific questions arise.&lt;/p&gt;
  1534.  
  1535.  
  1536.  
  1537. &lt;p&gt;Building a large space telescope typically takes about two decades. The &lt;a href="https://chandra.harvard.edu/"&gt;Chandra&lt;/a&gt; and &lt;a href="https://www.esa.int/Science_Exploration/Space_Science/XMM-Newton"&gt;XMM-Newton&lt;/a&gt; space telescopes took &lt;a href="https://chandra.harvard.edu/about/axaf_mission.html"&gt;23 years&lt;/a&gt; and &lt;a href="https://www.aanda.org/articles/aa/abs/2001/01/aaxmm39/aaxmm39.html"&gt;15 years&lt;/a&gt; to build, respectively. They were designed to observe X-rays coming from hot gas around black holes and galaxy clusters, and were launched very close together in 1999.&lt;/p&gt;
  1538.  
  1539. &lt;p&gt;They were followed by Japan’s &lt;a href="https://www.isas.jaxa.jp/en/missions/spacecraft/past/hitomi.html"&gt;Hitomi X-ray satellite&lt;/a&gt;, which took &lt;a href="https://pos.sissa.it/255/073"&gt;18 years&lt;/a&gt; to build, and the German &lt;a href="https://www.mpe.mpg.de/eROSITA"&gt;eRosita instrument&lt;/a&gt; on Russia’s &lt;a href="https://en.wikipedia.org/wiki/Spektr-RG"&gt;Spektr-RG&lt;/a&gt; space observatory, which took &lt;a href="https://arxiv.org/pdf/1209.3114"&gt;20 years&lt;/a&gt;. &lt;/p&gt;
  1540.  
  1541. &lt;p&gt;Similar timescales apply to the European Space Agency’s &lt;a href="https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1989-062B"&gt;Hipparcos&lt;/a&gt; and &lt;a href="https://www.esa.int/Science_Exploration/Space_Science/Gaia"&gt;Gaia&lt;/a&gt; space telescopes, which have &lt;a href="https://www.aanda.org/component/toc/?task=topic&amp;amp;id=922"&gt;mapped all the stars&lt;/a&gt; in the Milky Way. The &lt;a href="https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1989-089A"&gt;Cobe&lt;/a&gt; and &lt;a href="https://www.esa.int/Enabling_Support/Operations/Planck"&gt;Planck&lt;/a&gt; missions to study the microwave-light afterglow of the Big Bang also took two decades. Precise dates depend how you count, and a few exceptions have been &lt;a href="https://www.elizabethafrank.com/colliding-worlds/fbc"&gt;“faster, better, cheaper”&lt;/a&gt;, but national space agencies are generally risk averse and slow when developing these projects.&lt;/p&gt;
  1542.  
  1543. &lt;figure class="align-center "&gt;
  1544.            &lt;img alt="Remnants of star around a black hole - artwork" src="https://images.theconversation.com/files/625301/original/file-20241012-15-ds84dg.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;fit=clip" srcset="https://images.theconversation.com/files/625301/original/file-20241012-15-ds84dg.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=425&amp;amp;fit=crop&amp;amp;dpr=1 600w, https://images.theconversation.com/files/625301/original/file-20241012-15-ds84dg.jpg?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=425&amp;amp;fit=crop&amp;amp;dpr=2 1200w, https://images.theconversation.com/files/625301/original/file-20241012-15-ds84dg.jpg?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=425&amp;amp;fit=crop&amp;amp;dpr=3 1800w, https://images.theconversation.com/files/625301/original/file-20241012-15-ds84dg.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=534&amp;amp;fit=crop&amp;amp;dpr=1 754w, https://images.theconversation.com/files/625301/original/file-20241012-15-ds84dg.jpg?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=534&amp;amp;fit=crop&amp;amp;dpr=2 1508w, https://images.theconversation.com/files/625301/original/file-20241012-15-ds84dg.jpg?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=534&amp;amp;fit=crop&amp;amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"&gt;
  1545.            &lt;figcaption&gt;
  1546.              &lt;span class="caption"&gt;Chandra and XMM-Newton were launched to study X-rays from hot gas around black holes.&lt;/span&gt;
  1547.              &lt;span class="attribution"&gt;&lt;a class="source" href="https://www.eso.org/public/images/eso1644b/"&gt;ESO, Esa/Hubble, M. Kornmesser&lt;/a&gt;, &lt;a class="license" href="http://creativecommons.org/licenses/by/4.0/"&gt;CC BY&lt;/a&gt;&lt;/span&gt;
  1548.            &lt;/figcaption&gt;
  1549.          &lt;/figure&gt;
  1550.  
  1551. &lt;p&gt;The latest space telescopes are therefore millennials. They were designed at a time when astronomers had measured the universe’s &lt;a href="https://www.nobelprize.org/prizes/physics/2006/summary/"&gt;newborn expansion&lt;/a&gt; following the Big Bang, and also its &lt;a href="https://www.nobelprize.org/prizes/physics/2011/summary/"&gt;old-age, accelerating expansion&lt;/a&gt;. Their main goal now is to fill the gap –- because, surprisingly, interpolations from early times to late times don’t meet in the middle. &lt;/p&gt;
  1552.  
  1553. &lt;p&gt;&lt;a href="https://www.youtube.com/watch?v=c8RopZsgbfM"&gt;The measured rates&lt;/a&gt; for the expansion of the universe are inconsistent, as are results for the &lt;a href="https://theconversation.com/the-universe-is-smoother-than-the-standard-model-of-cosmology-suggests-so-is-the-theory-broken-238098"&gt;clumpiness of matter&lt;/a&gt; in the cosmos. Both measurements create challenges for our theories of how the universe evolved.&lt;/p&gt;
  1554.  
  1555. &lt;p&gt;Observing the middle age of the universe requires telescopes operating at long wavelengths, because &lt;a href="https://www.roe.ac.uk/%7Ejap/book/expandspace.pdf"&gt;light from distant galaxies is stretched&lt;/a&gt; by the time it reaches us. So, Webb has infrared zoom cameras, while the European Space Agency’s &lt;a href="https://www.esa.int/Science_Exploration/Space_Science/Euclid"&gt;Euclid space telescope&lt;/a&gt;, launched in 2023, and Nasa’s &lt;a href="https://roman.gsfc.nasa.gov/"&gt;Nancy Grace Roman telescope&lt;/a&gt;, which is set to launch in 2026, both have infrared wide-angle views.&lt;/p&gt;
  1556.  
  1557. &lt;h2&gt;Three buses come along at once&lt;/h2&gt;
  1558.  
  1559. &lt;p&gt;&lt;a href="https://www.space.com/22437-main-sequence-star.html"&gt;Most stars&lt;/a&gt; shine in ultraviolet and infrared colours that are blocked by the Earth’s atmosphere, as well as the colours our eyes evolved to see. &lt;/p&gt;
  1560.  
  1561. &lt;p&gt;Extra colours are useful. For example, we can weigh stars on the other side of our galaxy because &lt;a href="https://www.aanda.org/articles/aa/full_html/2018/12/aa33546-18/aa33546-18.html"&gt;massive stars are bright in infrared&lt;/a&gt;, while smaller ones are faint – and they stay that way throughout their lifetimes. However, we know where stars are being born because only &lt;a href="https://www.mdpi.com/2075-4434/8/2/43"&gt;young stars emit ultraviolet light&lt;/a&gt;.&lt;/p&gt;
  1562.  
  1563. &lt;p&gt;In addition, independent measurements of the same thing are vital for rigorous science. Infrared telescopes, for example, can &lt;a href="https://iopscience.iop.org/article/10.3847/1538-4365/aa96b0"&gt;work together&lt;/a&gt; and have already made &lt;a href="https://www.uibk.ac.at/en/newsroom/2024/euclid-finds-thousands-of-new-galaxies/"&gt;surprising discoveries&lt;/a&gt;. But it’s not great for diversity that the Webb, Euclid and Roman space telescopes all see infrared colours. &lt;/p&gt;
  1564.  
  1565. &lt;p&gt;Hubble’s visible light camera has just been &lt;a href="https://hst-docs.stsci.edu/hsp/hst-general-science-policies/nasa-hubble-operational-paradigm-change-review-and-hubble-observations"&gt;switched off&lt;/a&gt; due to budget cuts. Nasa will not swing back to ultraviolet wavelengths until the 2030s, with the &lt;a href="https://www.ipac.caltech.edu/project/uvex"&gt;Ultraviolet Explorer&lt;/a&gt; and &lt;a href="https://habitableworldsobservatory.org/"&gt;Habitable Worlds Observatory&lt;/a&gt;.&lt;/p&gt;
  1566.  
  1567.  
  1568.  
  1569. &lt;p&gt;Earthly politics gets in the way, too. Data from China’s Hubble-class space telescope, &lt;a href="https://www.space.com/china-space-telescope-xuntian"&gt;Xuntian&lt;/a&gt;, is unlikely to be shared internationally. And in protest at Russia’s invasion of Ukraine, in February 2022 Germany &lt;a href="https://www.space.com/germany-halts-russia-black-hole-telescope-space-cooperation"&gt;switched off&lt;/a&gt; its eRosita X-ray instrument that had been operating perfectly, in collaboration with Russia, a million miles from Earth.&lt;/p&gt;
  1570.  
  1571. &lt;p&gt;Cheap commercial launches may save the day. Euclid was to have lifted off on a Russian Soyuz rocket from a &lt;a href="https://www.esa.int/Enabling_Support/Space_Transportation/Europe_s_Spaceport/Europe_s_Spaceport2"&gt;European Space Agency spaceport&lt;/a&gt; in French Guiana. When Russia &lt;a href="https://www.independent.co.uk/space/russia-soyuz-launches-european-spaceport-french-guiana-b2024998.html"&gt;ended operations&lt;/a&gt; there in tit-for-tat reprisals, Euclid’s launch &lt;a href="https://spacenews.com/spacex-to-launch-european-astronomy-mission/"&gt;was successfully switched&lt;/a&gt; at the last minute to a SpaceX Falcon 9 rocket. &lt;/p&gt;
  1572.  
  1573. &lt;p&gt;If large telescopes can also be &lt;a href="https://www.universetoday.com/151326/teeny-tiny-cubesats-could-have-deployable-mirrors-like-james-webb/"&gt;folded&lt;/a&gt; inside shoebox-size &lt;a href="https://www.nasa.gov/what-are-smallsats-and-cubesats/"&gt;“cubesat”&lt;/a&gt; satellites, the lower cost would make it viable for them to fail. Tolerating risk creates a virtuous circle that makes missions even cheaper. &lt;/p&gt;
  1574.  
  1575. &lt;p&gt;Telescopes are also being tried in innovative locations such as &lt;a href="https://theconversation.com/how-a-balloon-borne-experiment-can-do-the-job-of-the-hubble-space-telescope-225906"&gt;giant helium balloons&lt;/a&gt; and &lt;a href="https://skyandtelescope.org/astronomy-news/sofia-airborne-observatory-has-taken-its-final-flight/"&gt;aeroplanes&lt;/a&gt;. One day, they might also be &lt;a href="https://www.newscientist.com/article/dn28323-china-has-had-a-telescope-on-the-moon-for-the-past-two-years/"&gt;deployed on the Moon&lt;/a&gt;, where the environment &lt;a href="https://theconversation.com/building-telescopes-on-the-moon-could-transform-astronomy-and-its-becoming-an-achievable-goal-203308"&gt;is advantageous&lt;/a&gt; for certain types of astronomy.&lt;/p&gt;
  1576.  
  1577.  
  1578.  
  1579. &lt;p&gt;But perhaps the most unusual telescope technology, which may bring the most unexpected discoveries, is gravitational wave detectors. &lt;a href="https://www.ligo.caltech.edu/page/gravitational-waves"&gt;Gravitational waves&lt;/a&gt; are not part of the electromagnetic spectrum, so we can’t see them. They are distortions, or “ripples”, in spacetime caused by some of the most violent and energetic processes in the universe. These &lt;a href="https://www.ligo.caltech.edu/page/gw-sources"&gt;might include&lt;/a&gt; a collision between two neutron stars (dense objects formed when massive stars run out of fuel), or a neutron star merging with a black hole. &lt;/p&gt;
  1580.  
  1581. &lt;p&gt;If telescopes are our eyes, gravitational wave detectors are &lt;a href="https://www.youtube.com/watch?v=dP6ZWew83_Q"&gt;our ears&lt;/a&gt;. But again, current &lt;a href="https://gcn.nasa.gov/missions/lvk"&gt;gravitational wave detectors&lt;/a&gt; on Earth are mere dry runs for the ones astronomers will ultimately &lt;a href="https://www.esa.int/Science_Exploration/Space_Science/LISA/Capturing_the_ripples_of_spacetime_LISA_gets_go-ahead"&gt;deploy in space&lt;/a&gt;.&lt;/p&gt;
  1582.  
  1583. &lt;p&gt;Asked what the next generation of observatories will discover, I have no idea. And that’s a good thing. The best science experiments shouldn’t just tell us about the things we expect to find, but also about the &lt;a href="https://www.youtube.com/watch?v=REWeBzGuzCc"&gt;unknown unknowns&lt;/a&gt;.&lt;/p&gt;&lt;img src="https://counter.theconversation.com/content/240078/count.gif" alt="The Conversation" width="1" height="1" /&gt;
  1584. &lt;p class="fine-print"&gt;&lt;em&gt;&lt;span&gt;Richard Massey receives funding from the UK Space Agency to support Euclid, and leads UK involvement in the SuperBIT balloon-born telescope. &lt;/span&gt;&lt;/em&gt;&lt;/p&gt;</content>
  1585.    <summary>Cosmology could be transformed by a new wave of telescopes – both on the ground and in space.</summary>
  1586.    <author>
  1587.      <name>Richard Massey, Professor of extragalactic astrophysics (dark matter and cosmology), Durham University</name>
  1588.      <foaf:homepage rdf:resource="https://theconversation.com/profiles/richard-massey-163739"/>
  1589.    </author>
  1590.    <rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
  1591.  </entry>
  1592.  <entry>
  1593.    <id>tag:theconversation.com,2011:article/241455</id>
  1594.    <published>2024-10-16T19:07:07Z</published>
  1595.    <updated>2024-10-16T19:07:07Z</updated>
  1596.    <link rel="alternate" type="text/html" href="https://theconversation.com/new-research-shows-most-space-rocks-crashing-into-earth-come-from-a-single-source-241455"/>
  1597.    <title>New research shows most space rocks crashing into Earth come from a single source</title>
  1598.    <content type="html">&lt;figure&gt;&lt;img src="https://images.theconversation.com/files/626077/original/file-20241015-15-ozid30.jpg?ixlib=rb-4.1.0&amp;amp;rect=4%2C116%2C2871%2C1793&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=496&amp;amp;fit=clip" /&gt;&lt;figcaption&gt;&lt;span class="caption"&gt;&lt;/span&gt; &lt;span class="attribution"&gt;&lt;a class="source" href="https://www.shutterstock.com/image-photo/perseid-meteor-shower-collage-photos-taken-1478713262"&gt;Makarov Konstantin/Shutterstock&lt;/a&gt;&lt;/span&gt;&lt;/figcaption&gt;&lt;/figure&gt;&lt;p&gt;The sight of a fireball streaking across the sky brings wonder and excitement to children and adults alike. It’s a reminder that Earth is part of a much larger and incredibly dynamic system. &lt;/p&gt;
  1599.  
  1600. &lt;p&gt;Each year, &lt;a href="https://pubs.geoscienceworld.org/gsa/geology/article/48/7/683/584575/The-spatial-flux-of-Earth-s-meteorite-falls-found"&gt;roughly 17,000&lt;/a&gt; of these fireballs not only enter Earth’s atmosphere, but survive the perilous journey to the surface. This gives scientists a valuable chance to study these rocky visitors from outer space. &lt;/p&gt;
  1601.  
  1602. &lt;p&gt;Scientists know that while some of these meteorites come from the Moon and Mars, the majority come from asteroids. But two separate studies published in Nature today have gone a step further. The research was led by &lt;a href="https://www.nature.com/articles/s41586-024-08006-7"&gt;Miroslav Brož&lt;/a&gt; from Charles University in the Czech Republic, and &lt;a href="https://www.nature.com/articles/s41586-024-08007-6"&gt;Michaël Marsset&lt;/a&gt; from the European Southern Observatory in Chile. &lt;/p&gt;
  1603.  
  1604. &lt;p&gt;The papers trace the origin of most meteorites to just a handful of asteroid breakup events – and possibly even individual asteroids. In turn, they build our understanding of the events that shaped the history of the Earth – and the entire solar system. &lt;/p&gt;
  1605.  
  1606. &lt;h2&gt;What is a meteorite?&lt;/h2&gt;
  1607.  
  1608. &lt;p&gt;Only when a fireball reaches Earth’s surface is it called a meteorite. They are commonly designated as three types: stony meteorites, iron meteorites, and stony-iron meteorites.  &lt;/p&gt;
  1609.  
  1610. &lt;p&gt;Stony meteorites come in two types. &lt;/p&gt;
  1611.  
  1612. &lt;p&gt;The most common are the chondrites, which have round objects inside that appear to have formed as melt droplets. These comprise 85% of all meteorites found on Earth. &lt;/p&gt;
  1613.  
  1614. &lt;p&gt;Most are known as “ordinary chondrites”. They are then divided into three broad classes – H, L and LL – based on the iron content of the meteorites and the distribution of iron and magnesium in the major minerals olivine and pyroxene. These silicate minerals are the mineral building blocks of our Solar System and are common on Earth, being present in basalt.&lt;/p&gt;
  1615.  
  1616. &lt;p&gt;“Carbonaceous chondrites” are a distinct group. They contain high amounts of water in clay minerals, and organic materials such as amino acids. Chondrites have never been melted and are direct samples of the dust that originally formed the solar system. &lt;/p&gt;
  1617.  
  1618. &lt;p&gt;The less common of the two types of stony meteorites are the so-called “achondrites”. These do not have the distinctive round particles of chondrites, because they experienced melting on planetary bodies.&lt;/p&gt;
  1619.  
  1620. &lt;figure class="align-center zoomable"&gt;
  1621.            &lt;a href="https://images.theconversation.com/files/626108/original/file-20241016-17-l1i24q.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=1000&amp;amp;fit=clip"&gt;&lt;img alt="Black rock with triangle-pattern texture." src="https://images.theconversation.com/files/626108/original/file-20241016-17-l1i24q.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;fit=clip" srcset="https://images.theconversation.com/files/626108/original/file-20241016-17-l1i24q.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=448&amp;amp;fit=crop&amp;amp;dpr=1 600w, https://images.theconversation.com/files/626108/original/file-20241016-17-l1i24q.jpg?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=448&amp;amp;fit=crop&amp;amp;dpr=2 1200w, https://images.theconversation.com/files/626108/original/file-20241016-17-l1i24q.jpg?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=448&amp;amp;fit=crop&amp;amp;dpr=3 1800w, https://images.theconversation.com/files/626108/original/file-20241016-17-l1i24q.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=562&amp;amp;fit=crop&amp;amp;dpr=1 754w, https://images.theconversation.com/files/626108/original/file-20241016-17-l1i24q.jpg?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=562&amp;amp;fit=crop&amp;amp;dpr=2 1508w, https://images.theconversation.com/files/626108/original/file-20241016-17-l1i24q.jpg?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=562&amp;amp;fit=crop&amp;amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"&gt;&lt;/a&gt;
  1622.            &lt;figcaption&gt;
  1623.              &lt;span class="caption"&gt;An iron-nickel meteorite found near Fort Stockton, Texas, in 1952.&lt;/span&gt;
  1624.              &lt;span class="attribution"&gt;&lt;a class="source" href="https://images.nasa.gov/details/PIA12192"&gt;JPL/Smithsonian Institution&lt;/a&gt;&lt;/span&gt;
  1625.            &lt;/figcaption&gt;
  1626.          &lt;/figure&gt;
  1627.  
  1628. &lt;h2&gt;The asteroid belt&lt;/h2&gt;
  1629.  
  1630. &lt;p&gt;Asteroids are the primary sources of meteorites. &lt;/p&gt;
  1631.  
  1632. &lt;p&gt;Most asteroids reside in a dense belt between Mars and Jupiter. The asteroid belt itself consists of millions of asteroids swept around and marshalled by the gravitational force of Jupiter. &lt;/p&gt;
  1633.  
  1634. &lt;p&gt;The interactions with Jupiter can perturb asteroid orbits and cause collisions. This results in debris, which can aggregate into rubble pile asteroids. These then take on lives of their own. &lt;/p&gt;
  1635.  
  1636. &lt;p&gt;It is asteroids of this type which the recent &lt;a href="https://theconversation.com/hayabusas-asteroid-dust-reveals-space-secrets-3075"&gt;Hayabusa&lt;/a&gt; and &lt;a href="https://theconversation.com/7-years-billions-of-kilometres-a-handful-of-dust-nasa-just-brought-back-the-largest-ever-asteroid-sample-214151"&gt;Osiris-REx&lt;/a&gt; missions visited and returned samples from. These missions established the connection between distinct asteroid types and the meteorites that fall to Earth.&lt;/p&gt;
  1637.  
  1638. &lt;p&gt;S-class asteroids (akin to stony meteorites) are found on the inner regions of the belt, while C-class carbonaceous asteroids (akin to carbonaceous chondrites) are more commonly found in the outer regions of the belt. &lt;/p&gt;
  1639.  
  1640. &lt;p&gt;But, as the two Nature studies show, we can relate a specific meteorite type to its specific source asteroid in the main belt.&lt;/p&gt;
  1641.  
  1642. &lt;figure class="align-center zoomable"&gt;
  1643.            &lt;a href="https://images.theconversation.com/files/626075/original/file-20241015-15-khclyh.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=1000&amp;amp;fit=clip"&gt;&lt;img alt="Orbit of Mercury, Venus, Earth, Mars and Jupiter around the sun, with a dense cluster of asteroids between Mars and Jupiter." src="https://images.theconversation.com/files/626075/original/file-20241015-15-khclyh.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;fit=clip" srcset="https://images.theconversation.com/files/626075/original/file-20241015-15-khclyh.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=597&amp;amp;fit=crop&amp;amp;dpr=1 600w, https://images.theconversation.com/files/626075/original/file-20241015-15-khclyh.png?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=597&amp;amp;fit=crop&amp;amp;dpr=2 1200w, https://images.theconversation.com/files/626075/original/file-20241015-15-khclyh.png?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=597&amp;amp;fit=crop&amp;amp;dpr=3 1800w, https://images.theconversation.com/files/626075/original/file-20241015-15-khclyh.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=750&amp;amp;fit=crop&amp;amp;dpr=1 754w, https://images.theconversation.com/files/626075/original/file-20241015-15-khclyh.png?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=750&amp;amp;fit=crop&amp;amp;dpr=2 1508w, https://images.theconversation.com/files/626075/original/file-20241015-15-khclyh.png?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=750&amp;amp;fit=crop&amp;amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"&gt;&lt;/a&gt;
  1644.            &lt;figcaption&gt;
  1645.              &lt;span class="caption"&gt;Artist’s graphic of the asteroid belt between Mars and Jupiter.&lt;/span&gt;
  1646.              &lt;span class="attribution"&gt;&lt;a class="source" href="https://science.nasa.gov/resource/asteroid-belt/"&gt;NASA/McREL&lt;/a&gt;&lt;/span&gt;
  1647.            &lt;/figcaption&gt;
  1648.          &lt;/figure&gt;
  1649.  
  1650. &lt;h2&gt;One family of asteroids&lt;/h2&gt;
  1651.  
  1652. &lt;p&gt;The two new studies place the sources of ordinary chondrite types into specific asteroid families – and most likely specific asteroids.  This work requires painstaking back-tracking of meteoroid trajectories, observations of individual asteroids, and detailed modelling of the orbital evolution of parent bodies.&lt;/p&gt;
  1653.  
  1654. &lt;p&gt;&lt;a href="https://www.nature.com/articles/s41586-024-08006-7"&gt;The study&lt;/a&gt; led by Miroslav Brož reports that ordinary chondrites originate from collisions between asteroids larger than 30 kilometres in diameter that occurred less than 30 million years ago.&lt;/p&gt;
  1655.  
  1656. &lt;p&gt;The Koronis and Massalia asteroid families provide appropriate body sizes and are in a position that leads to material falling to Earth, based on detailed computer modelling. Of these families, asteroids Koronis and Karin are likely the dominant sources of H chondrites. Massalia (L) and Flora (LL) families are by far the main sources of L- and LL-like meteorites. &lt;/p&gt;
  1657.  
  1658. &lt;p&gt;&lt;a href="https://www.nature.com/articles/s41586-024-08007-6"&gt;The study&lt;/a&gt; led by Michaël Marsset further documents the origin of L chondrite meteorites from Massalia. &lt;/p&gt;
  1659.  
  1660. &lt;p&gt;It compiled spectroscopic data – that is, characteristic light intensities which can be fingerprints of different molecules – of asteroids in the belt between Mars and Jupiter. This showed that the composition of L chondrite meteorites on Earth is very similar to that of the Massalia family of asteroids. &lt;/p&gt;
  1661.  
  1662. &lt;p&gt;The scientists then used computer modelling to show an asteroid collision that occurred roughly 470 million years ago formed the Massalia family. Serendipitously, this collision also resulted in abundant fossil meteorites in Ordovician limestones in Sweden.&lt;/p&gt;
  1663.  
  1664. &lt;p&gt;In determining the source asteroid body, these reports provide the foundations for missions to visit the asteroids responsible for the most common outerspace visitors to Earth.  In understanding these source asteroids, we can view the events that shaped our planetary system.&lt;/p&gt;&lt;img src="https://counter.theconversation.com/content/241455/count.gif" alt="The Conversation" width="1" height="1" /&gt;
  1665. &lt;p class="fine-print"&gt;&lt;em&gt;&lt;span&gt;Trevor Ireland receives funding from the Australian Research Council for research into the samples returned by the Hayabusa and Osiris-REx missions.  He is a past President of the Meteoritical Society, the international organisation responsible for classification and cataloguing meteorites. &lt;/span&gt;&lt;/em&gt;&lt;/p&gt;</content>
  1666.    <summary>Two new studies show that the majority of meteorites originate from just one family of asteroids between Mars and Jupiter.</summary>
  1667.    <author>
  1668.      <name>Trevor Ireland, Professor, School of the Environment, The University of Queensland</name>
  1669.      <foaf:homepage rdf:resource="https://theconversation.com/profiles/trevor-ireland-20327"/>
  1670.    </author>
  1671.    <rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
  1672.  </entry>
  1673.  <entry>
  1674.    <id>tag:theconversation.com,2011:article/236849</id>
  1675.    <published>2024-10-11T17:36:50Z</published>
  1676.    <updated>2024-10-11T17:36:50Z</updated>
  1677.    <link rel="alternate" type="text/html" href="https://theconversation.com/comet-tsuchinshan-atlas-is-a-halloween-visitor-from-the-spooky-oort-cloud-the-invisible-bubble-thats-home-to-countless-space-objects-236849"/>
  1678.    <title>Comet Tsuchinshan-ATLAS is a Halloween visitor from the spooky Oort Cloud − the invisible bubble that’s home to countless space objects</title>
  1679.    <content type="html">&lt;figure&gt;&lt;img src="https://images.theconversation.com/files/625220/original/file-20241011-16-fujgiu.jpg?ixlib=rb-4.1.0&amp;amp;rect=3%2C7%2C2375%2C1648&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=496&amp;amp;fit=clip" /&gt;&lt;figcaption&gt;&lt;span class="caption"&gt;View of the Tsuchinshan-ATLAS comet on Sept. 30, 2024, from Monfrague National Park in Spain.&lt;/span&gt; &lt;span class="attribution"&gt;&lt;a class="source" href="https://www.gettyimages.com/detail/news-photo/comet-c-2023-a3-known-also-as-the-comet-of-the-century-is-news-photo/2175354817?adppopup=true"&gt;Marcos del Mazo/LightRocket via Getty Images&lt;/a&gt;&lt;/span&gt;&lt;/figcaption&gt;&lt;/figure&gt;&lt;p&gt;The human mind may find it difficult to conceptualize: a cosmic cloud so colossal it surrounds the Sun and eight planets as it extends trillions of miles into deep space. &lt;/p&gt;
  1680.  
  1681. &lt;p&gt;The spherical shell known as the Oort Cloud is, for all practical purposes, invisible. Its constituent particles are spread so thinly, and so far from the light of any star, including the Sun, that astronomers simply cannot see the cloud, even though it envelops us like a blanket. &lt;/p&gt;
  1682.  
  1683. &lt;p&gt;It is also theoretical. Astronomers infer the Oort Cloud is there because it’s the only logical explanation for the arrival of a certain class of comets that sporadically visit our solar system. The cloud, it turns out, is basically a gigantic reservoir that &lt;a href="https://science.nasa.gov/solar-system/oort-cloud/facts/"&gt;may hold billions of icy celestial bodies&lt;/a&gt;. &lt;/p&gt;
  1684.  
  1685. &lt;p&gt;Two of those bodies will pass by Earth in the days leading up to Halloween. &lt;a href="https://theskylive.com/c2023a3-info"&gt;Tsuchinshan-ATLAS&lt;/a&gt;, also known as Comet C/2023 A3, will be at its brightest, and likely visible to the naked eye, for a week or two after Oct. 12, the day it’s closest to Earth – just look to the western sky shortly after sunset. As the days pass, the comet will get fainter and move to a higher part of the sky. &lt;/p&gt;
  1686.  
  1687. &lt;figure&gt;
  1688.            &lt;iframe width="440" height="260" src="https://www.youtube.com/embed/FPMMFIB9sjY?wmode=transparent&amp;amp;start=0" frameborder="0" allowfullscreen=""&gt;&lt;/iframe&gt;
  1689.            &lt;figcaption&gt;&lt;span class="caption"&gt;A view of comet Tsuchinshan-ATLAS from the International Space Station.&lt;/span&gt;&lt;/figcaption&gt;
  1690.          &lt;/figure&gt;
  1691.  
  1692. &lt;p&gt;The second comet, &lt;a href="https://theskylive.com/how-far-is-c2024a1"&gt;C/2024 S1 (ATLAS)&lt;/a&gt;, just discovered on Sept. 27, should be visible around the end of October. The comet will pass closest to Earth on Oct. 24 – look low in the eastern sky just before sunrise. Then, after swinging around the Sun, the comet may reappear in the western night sky right around Halloween. It’s possible, however, that it could disintegrate, in part or in whole, as sometimes happens when comets pass by the Sun – and this one will come within 1 million miles (1.6 million kilometers) of our star.&lt;/p&gt;
  1693.  
  1694. &lt;p&gt;&lt;a href="https://wray.eas.gatech.edu/"&gt;As a planetary astronomer&lt;/a&gt;, I’m particularly curious about the Oort Cloud and the icy bodies inhabiting it. The Cloud’s residents may be a reason why life ignited on Earth; crashing on our planet eons ago, these ice bodies may have supplied &lt;a href="https://www.jpl.nasa.gov/news/comet-provides-new-clues-to-origins-of-earths-oceans/"&gt;at least some of the water&lt;/a&gt; that all life requires. At the same time, these same objects pose an ever-present threat to Earth’s continuation – &lt;a href="https://earthsky.org/space/younger-dryas-comet-burst-crashed-earths-climate/"&gt;and our survival&lt;/a&gt;.&lt;/p&gt;
  1695.  
  1696. &lt;h2&gt;Billions of comets&lt;/h2&gt;
  1697.  
  1698. &lt;p&gt;If an Oort Cloud object finds its way to the inner solar system, its ices vaporize. That process produces a tail of debris that becomes visible as a comet.&lt;/p&gt;
  1699.  
  1700. &lt;p&gt;Some of these bodies, known as &lt;a href="https://astronomy.swin.edu.au/cosmos/l/Long-period+Comets"&gt;long-period comets&lt;/a&gt;, have orbits of hundreds, thousands or even millions of years, like Tsuchinshan-ATLAS. This is unlike the so-called &lt;a href="https://lco.global/spacebook/solar-system/comets-kuiper-belt-and-oort-cloud/#:%7E"&gt;short-period comets&lt;/a&gt;, which do not visit the Oort Cloud and have comparatively quick orbits. &lt;a href="https://science.nasa.gov/solar-system/comets/1p-halley/"&gt;Halley’s comet&lt;/a&gt;, which cuts a path through the solar system and orbits the Sun every 76 years or so, is one of them. &lt;/p&gt;
  1701.  
  1702. &lt;p&gt;The 20th-century Dutch astronomer Jan Oort, intrigued by the long-period comets, &lt;a href="https://articles.adsabs.harvard.edu/pdf/1950BAN....11...91O"&gt;wrote a paper on them in 1950&lt;/a&gt;. He noted about 20 of the comets had an average distance from the Sun that was more than 10,000 astronomical units. This was astounding; just one AU is the distance of the Earth from the Sun, which is &lt;a href="https://science.nasa.gov/learning-resources/how-big-is-the-solar-system/"&gt;about 93 million miles&lt;/a&gt;. Multiply 93 million by 10,000, and you’ll find these comets come from over a trillion miles away. What’s more, Oort suggested, they were not necessarily the cloud’s outermost objects. &lt;/p&gt;
  1703.  
  1704. &lt;p&gt;Nearly 75 years after Oort’s paper, astronomers still can’t directly image this part of space. But they do estimate the Oort Cloud spans up to 10 trillion miles from the Sun, which is almost halfway to &lt;a href="https://earthsky.org/astronomy-essentials/proxima-centauri-our-suns-nearest-neighbor/"&gt;Proxima Centauri&lt;/a&gt;, the next closest star. &lt;/p&gt;
  1705.  
  1706. &lt;p&gt;The long-period comets spend most of their time at those vast distances, making only brief and rapid visits close to the Sun as they come in from all directions. Oort speculated the cloud contained 100 billion of these icy objects. That may be as numerous as the &lt;a href="https://imagine.gsfc.nasa.gov/science/objects/milkyway1.html#:%7E"&gt;number of stars in our galaxy&lt;/a&gt;.&lt;/p&gt;
  1707.  
  1708. &lt;p&gt;How did they get there? Oort suggested, and modern simulations have confirmed, that these icy bodies could have initially formed near &lt;a href="https://science.nasa.gov/jupiter/"&gt;Jupiter, the solar system’s largest planet&lt;/a&gt;. Perhaps these objects had their orbits around the Sun disturbed by Jupiter – similar to how NASA spacecraft bound for destinations from Saturn to Pluto have typically &lt;a href="https://science.nasa.gov/learn/basics-of-space-flight/primer/"&gt;swung by the giant planet&lt;/a&gt; to accelerate their journeys outward. &lt;/p&gt;
  1709.  
  1710. &lt;p&gt;Some of these objects would have escaped the solar system permanently, becoming &lt;a href="https://knowablemagazine.org/content/article/physical-world/2024/detect-interstellar-objects-oumuamua-borisov-clues-to-exoplanets"&gt;interstellar objects&lt;/a&gt;. But others would have ended up with orbits like those of the long-period comets.&lt;/p&gt;
  1711.  
  1712. &lt;figure class="align-center zoomable"&gt;
  1713.            &lt;a href="https://images.theconversation.com/files/625040/original/file-20241010-15-us6m1c.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=1000&amp;amp;fit=clip"&gt;&lt;img alt="An artistic illustration of the solar system and the Oort Cloud." src="https://images.theconversation.com/files/625040/original/file-20241010-15-us6m1c.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;fit=clip" srcset="https://images.theconversation.com/files/625040/original/file-20241010-15-us6m1c.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=337&amp;amp;fit=crop&amp;amp;dpr=1 600w, https://images.theconversation.com/files/625040/original/file-20241010-15-us6m1c.jpg?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=337&amp;amp;fit=crop&amp;amp;dpr=2 1200w, https://images.theconversation.com/files/625040/original/file-20241010-15-us6m1c.jpg?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=337&amp;amp;fit=crop&amp;amp;dpr=3 1800w, https://images.theconversation.com/files/625040/original/file-20241010-15-us6m1c.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=424&amp;amp;fit=crop&amp;amp;dpr=1 754w, https://images.theconversation.com/files/625040/original/file-20241010-15-us6m1c.jpg?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=424&amp;amp;fit=crop&amp;amp;dpr=2 1508w, https://images.theconversation.com/files/625040/original/file-20241010-15-us6m1c.jpg?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=424&amp;amp;fit=crop&amp;amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"&gt;&lt;/a&gt;
  1714.            &lt;figcaption&gt;
  1715.              &lt;span class="caption"&gt;An illustration of the solar system and the Oort Cloud. The numbers on the graph depict AUs, or astronomical units. Note the location of Voyager 2, which will take another 30,000 years to fly out of the Cloud.&lt;/span&gt;
  1716.              &lt;span class="attribution"&gt;&lt;a class="source" href="https://astrobiology.nasa.gov/news/revised-data-sets-for-oort-cloud-comets/"&gt;NASA&lt;/a&gt;&lt;/span&gt;
  1717.            &lt;/figcaption&gt;
  1718.          &lt;/figure&gt;
  1719.  
  1720. &lt;h2&gt;Threats to Earth&lt;/h2&gt;
  1721.  
  1722. &lt;p&gt;Long-period comets &lt;a href="https://doi.org/10.1016/j.jsse.2018.07.002"&gt;present a particular potential danger to Earth&lt;/a&gt;. Because they are so far from our Sun, their orbits are readily altered by the gravity of other stars. That means scientists have no idea when or where one will appear, until it does, suddenly. By then, it’s typically closer than Jupiter and moving rapidly, at tens of thousands of miles per hour. Indeed, the fictional comet that doomed Earth in the film “&lt;a href="https://www.imdb.com/title/tt11286314/"&gt;Don’t Look Up&lt;/a&gt;” &lt;a href="https://www.syfy.com/dont-look-up-science-behind-planet-killer-comet"&gt;came from the Oort Cloud&lt;/a&gt;.&lt;/p&gt;
  1723.  
  1724. &lt;p&gt;New Oort Cloud comets are discovered all the time, a dozen or so per year in recent years. The odds of any of them colliding with Earth are extremely low. &lt;a href="https://bigthink.com/starts-with-a-bang/largest-comet-earth/"&gt;But it is possible&lt;/a&gt;. The recent success of &lt;a href="https://science.nasa.gov/mission/dart/"&gt;NASA’s DART mission&lt;/a&gt;, which &lt;a href="https://theconversation.com/nasa-successfully-shifted-an-asteroids-orbit-dart-spacecraft-crashed-into-and-moved-dimorphos-192317"&gt;altered the orbit of a small asteroid&lt;/a&gt;, demonstrates one plausible approach to fending off these small bodies. But that mission was developed after years of studying its target. A comet from the Oort Cloud may not offer that much time – maybe just months, weeks or even days. &lt;/p&gt;
  1725.  
  1726. &lt;p&gt;Or no time at all. &lt;a href="https://science.nasa.gov/solar-system/comets/oumuamua/"&gt;’Oumuamua&lt;/a&gt;, the odd little object that visited our solar system in 2017, was discovered not before but after its closest approach to Earth. Although ’Oumuamua is an interstellar object, and not from the Oort Cloud, the proposition still applies; one of these objects could sneak up on us, and the Earth would be defenseless.&lt;/p&gt;
  1727.  
  1728. &lt;p&gt;One way to prepare for these objects is to better understand their basic properties, including their size and composition. Toward this end, my colleagues and I work to characterize new long-period comets. The largest known one, &lt;a href="https://www.space.com/giant-comet-bernardinelli-bernstein-discovery-size-activity"&gt;Bernardinelli–Bernstein&lt;/a&gt;, discovered just three years ago, is roughly 75 miles (120 kilometers) across. Most known comets are much smaller, from one to a few miles, and some smaller ones are too faint for us to see. But newer telescopes are helping. In particular, the Rubin Observatory’s decade-long &lt;a href="https://kipac.stanford.edu/research/projects/vera-rubin-observatorys-legacy-survey-space-and-time"&gt;Legacy Survey of Space and Time&lt;/a&gt;, starting up in 2025, may double the list of known Oort Cloud comets, which now stands at about 4,500. &lt;/p&gt;
  1729.  
  1730. &lt;p&gt;The unpredictability of these objects makes them a challenging target for spacecraft, but the European Space Agency is preparing a mission to do just that: &lt;a href="https://www.cometinterceptor.space/"&gt;Comet Interceptor&lt;/a&gt;. With a launch planned for 2029, the probe will park in space until a suitable target from the Oort Cloud appears. Studying one of these ancient and pristine objects could offer scientists clues about the origins of the solar system. &lt;/p&gt;
  1731.  
  1732. &lt;p&gt;As for the comets now in Earth’s vicinity, it’s OK to look up. Unlike the comet in the DiCaprio movie, these two will not crash into the Earth. The nearest Tsuchinshan-ATLAS will get to us is about 44 million miles (70 million kilometers); C/2024 S1 (ATLAS), about 80 million miles (130 million kilometers). Sounds like a long way, but in space, that’s a near miss.&lt;/p&gt;&lt;img src="https://counter.theconversation.com/content/236849/count.gif" alt="The Conversation" width="1" height="1" /&gt;
  1733. &lt;p class="fine-print"&gt;&lt;em&gt;&lt;span&gt;James Wray receives funding from NASA. &lt;/span&gt;&lt;/em&gt;&lt;/p&gt;</content>
  1734.    <summary>Comet Tsuchinshan-ATLAS is one of 2 comets from the Oort Cloud passing by Earth in October 2024.</summary>
  1735.    <author>
  1736.      <name>James Wray, Professor of Earth and Atmospheric Sciences, Georgia Institute of Technology</name>
  1737.      <foaf:homepage rdf:resource="https://theconversation.com/profiles/james-wray-1506813"/>
  1738.    </author>
  1739.    <rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
  1740.  </entry>
  1741.  <entry>
  1742.    <id>tag:theconversation.com,2011:article/239814</id>
  1743.    <published>2024-10-07T12:20:41Z</published>
  1744.    <updated>2024-10-07T12:20:41Z</updated>
  1745.    <link rel="alternate" type="text/html" href="https://theconversation.com/nasa-wants-to-send-humans-to-mars-in-the-2030s-a-crewed-mission-could-unlock-some-of-the-red-planets-geologic-mysteries-239814"/>
  1746.    <title>NASA wants to send humans to Mars in the 2030s − a crewed mission could unlock some of the red planet’s geologic mysteries</title>
  1747.    <content type="html">&lt;figure&gt;&lt;img src="https://images.theconversation.com/files/622874/original/file-20241001-16-w1r4jm.jpg?ixlib=rb-4.1.0&amp;amp;rect=388%2C0%2C5176%2C2138&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=496&amp;amp;fit=clip" /&gt;&lt;figcaption&gt;&lt;span class="caption"&gt;Mars&amp;#39; craters come from ancient collisions during the formation of the solar system. &lt;/span&gt; &lt;span class="attribution"&gt;&lt;a class="source" href="https://newsroom.ap.org/detail/SpaceMarsRover/6d468fe05ab145809bbc7d6cf2801d5f/photo?Query=mars&amp;amp;mediaType=photo&amp;amp;sortBy=&amp;amp;dateRange=Anytime&amp;amp;totalCount=50&amp;amp;digitizationType=Digitized&amp;amp;currentItemNo=30&amp;amp;vs=true&amp;amp;vs=true"&gt;NASA/JPL-Caltech/Cornell University/Arizona State University via AP&lt;/a&gt;&lt;/span&gt;&lt;/figcaption&gt;&lt;/figure&gt;&lt;p&gt;NASA plans to send humans on a scientific round trip to Mars potentially as early as 2035. The trip will take about six to seven months each way and will cover up to &lt;a href="https://www.space.com/24701-how-long-does-it-take-to-get-to-mars.html"&gt;250 million miles (402 million kilometers) each way&lt;/a&gt;. The astronauts may spend as many as 500 days on the planet’s surface before returning to Earth.&lt;/p&gt;
  1748.  
  1749. &lt;p&gt;NASA’s &lt;a href="https://www.nasa.gov/humans-in-space/artemis/"&gt;Artemis program&lt;/a&gt; plans to return humans to the Moon this decade to practice and prepare for a Mars mission as early as the 2030s. While NASA has several reasons for pursuing such an ambitious mission, the biggest is scientific exploration and discovery.&lt;/p&gt;
  1750.  
  1751. &lt;p&gt;I’m &lt;a href="https://www.wm.edu/as/appliedscience/people/researchfaculty/levine-j.php"&gt;an atmospheric scientist and former NASA researcher&lt;/a&gt; involved in establishing the scientific questions a Mars mission would investigate. There are lots of mysteries to investigate on the red planet, including why Mars looks the way it does today, and whether it has ever hosted life, past or present. &lt;/p&gt;
  1752.  
  1753. &lt;figure class="align-center zoomable"&gt;
  1754.            &lt;a href="https://images.theconversation.com/files/622873/original/file-20241001-16-h8xfe7.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=1000&amp;amp;fit=clip"&gt;&lt;img alt="Mars, a dusty reddish planet, floating in space." src="https://images.theconversation.com/files/622873/original/file-20241001-16-h8xfe7.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;fit=clip" srcset="https://images.theconversation.com/files/622873/original/file-20241001-16-h8xfe7.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=600&amp;amp;fit=crop&amp;amp;dpr=1 600w, https://images.theconversation.com/files/622873/original/file-20241001-16-h8xfe7.jpg?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=600&amp;amp;fit=crop&amp;amp;dpr=2 1200w, https://images.theconversation.com/files/622873/original/file-20241001-16-h8xfe7.jpg?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=600&amp;amp;fit=crop&amp;amp;dpr=3 1800w, https://images.theconversation.com/files/622873/original/file-20241001-16-h8xfe7.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=754&amp;amp;fit=crop&amp;amp;dpr=1 754w, https://images.theconversation.com/files/622873/original/file-20241001-16-h8xfe7.jpg?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=754&amp;amp;fit=crop&amp;amp;dpr=2 1508w, https://images.theconversation.com/files/622873/original/file-20241001-16-h8xfe7.jpg?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=754&amp;amp;fit=crop&amp;amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"&gt;&lt;/a&gt;
  1755.            &lt;figcaption&gt;
  1756.              &lt;span class="caption"&gt;Studying Mars can tell researchers more about the formation of the solar system.&lt;/span&gt;
  1757.              &lt;span class="attribution"&gt;&lt;a class="source" href="https://newsroom.ap.org/detail/MarsPonds/94bf71418253420c859d80727043c4f3/photo?Query=mars&amp;amp;mediaType=photo&amp;amp;sortBy=&amp;amp;dateRange=Anytime&amp;amp;totalCount=5&amp;amp;digitizationType=Digitized&amp;amp;currentItemNo=3&amp;amp;vs=true"&gt;J. Bell/NASA via AP&lt;/a&gt;&lt;/span&gt;
  1758.            &lt;/figcaption&gt;
  1759.          &lt;/figure&gt;
  1760.  
  1761. &lt;h2&gt;Mars geology&lt;/h2&gt;
  1762.  
  1763. &lt;p&gt;Mars is &lt;a href="https://archive.org/details/travelersguideto00will"&gt;an intriguing planet&lt;/a&gt; from a geological and atmospheric perspective. It formed with the rest of the solar system &lt;a href="https://science.nasa.gov/solar-system/solar-system-facts/"&gt;about 4.6 billion years ago&lt;/a&gt;. Around 3.8 billion years ago, the &lt;a href="https://naturalhistory.si.edu/education/teaching-resources/life-science/early-life-earth-animal-origins"&gt;same time that life formed on Earth&lt;/a&gt;, early Mars was very Earth-like. It had &lt;a href="https://astrobiology.nasa.gov/news/water-on-mars-the-story-so-far/"&gt;abundant liquid water&lt;/a&gt; on its surface in the form of oceans, lakes and rivers and possessed a denser atmosphere.  &lt;/p&gt;
  1764.  
  1765. &lt;p&gt;While Mars’ surface is totally devoid of liquid water today, scientists have spotted evidence of those past lakes, rivers and even an ocean coastline on its surface. Its north and south poles are covered in frozen water, with a thin veneer of frozen carbon dioxide. At the south pole during the summer, the carbon dioxide veneer disappears, leaving the frozen water exposed.&lt;/p&gt;
  1766.  
  1767. &lt;p&gt;Today, Mars’ atmosphere is very thin and &lt;a href="https://shop.elsevier.com/books/the-photochemistry-of-atmospheres/levine/978-0-12-444920-6"&gt;about 95% carbon dioxide&lt;/a&gt;. It’s &lt;a href="https://www.cambridgescholars.com/product/978-1-5275-1172-9"&gt;filled with atmospheric dust&lt;/a&gt; from the surface, which gives the atmosphere of Mars its characteristic reddish color.&lt;/p&gt;
  1768.  
  1769. &lt;p&gt;Scientists know quite a bit about the planet’s surface from sending robotic missions, but there are still many interesting geologic features to investigate more closely. These features could tell researchers more about the solar system’s formation.&lt;/p&gt;
  1770.  
  1771. &lt;p&gt;The northern and southern hemispheres of Mars look very different. About one-third of the surface of Mars – mostly in its northern hemisphere – is 2 to 4 miles (3.2-6.4 kilometers) lower in elevation, called the &lt;a href="https://pubs.usgs.gov/publication/sim2888"&gt;northern lowlands&lt;/a&gt;. The northern lowlands have a few large craters but are relatively smooth. The southern two-thirds of the planet, called &lt;a href="https://www.britannica.com/place/Mars-planet/Southern-cratered-highlands"&gt;the southern highlands&lt;/a&gt;, has lots of &lt;a href="https://www.esa.int/Science_Exploration/Space_Science/Mars_Express/Promethei_Terra_southern_highlands_of_Mars"&gt;very old craters&lt;/a&gt;. &lt;/p&gt;
  1772.  
  1773. &lt;p&gt;Mars also has the &lt;a href="https://www.skyatnightmagazine.com/space-science/olympus-mons"&gt;largest volcanoes that scientists have observed&lt;/a&gt; in the solar system. Its surface is peppered with &lt;a href="https://en.wikipedia.org/wiki/List_of_craters_on_Mars"&gt;deep craters&lt;/a&gt; from asteroid and meteor impacts that occurred during the early history of Mars. Sending astronauts to study these features can help researchers understand how and when major events happened during the early history of Mars.&lt;/p&gt;
  1774.  
  1775. &lt;figure&gt;
  1776.            &lt;iframe width="440" height="260" src="https://www.youtube.com/embed/Cww3yVQpcjY?wmode=transparent&amp;amp;start=0" frameborder="0" allowfullscreen=""&gt;&lt;/iframe&gt;
  1777.            &lt;figcaption&gt;&lt;span class="caption"&gt;Mars’ volcanoes tower over any of the highest mountains on Earth.&lt;/span&gt;&lt;/figcaption&gt;
  1778.          &lt;/figure&gt;
  1779.  
  1780. &lt;h2&gt;Asking the right questions&lt;/h2&gt;
  1781.  
  1782. &lt;p&gt;NASA formed a panel called the Human Exploration of Mars Science Analysis Group to plan the future mission. I co-chaired the panel, with NASA scientist James B. Garvin, to develop and assess the &lt;a href="http://images.spaceref.com/news/2008/HEM-SAG_final_draft_4a_v2.pdf"&gt;key scientific questions about Mars&lt;/a&gt;. We wanted to figure out which research questions required a human mission to address, rather than cheaper robotic missions.  &lt;/p&gt;
  1783.  
  1784. &lt;p&gt;The panel came up with recommendations for several important scientific questions for human investigation on Mars. &lt;/p&gt;
  1785.  
  1786. &lt;p&gt;One question asks whether there’s life on the planet today. Remember, life on Earth formed about 3.8 billion years ago, when Earth and Mars were similar-looking planets that both had abundant liquid water and Mars had a denser atmosphere. &lt;/p&gt;
  1787.  
  1788. &lt;p&gt;Another question asks what sort of environmental changes led Mars to lose the widespread, plentiful liquid water on its surface, as well as some of its atmosphere. &lt;/p&gt;
  1789.  
  1790. &lt;p&gt;These questions, alongside other recommendations from the panel, made it into &lt;a href="https://www.nasa.gov/wp-content/uploads/2015/09/373665main_nasa-sp-2009-566.pdf?emrc=6dfe40"&gt;NASA’s architectural plan for sending humans to Mars&lt;/a&gt;. &lt;/p&gt;
  1791.  
  1792. &lt;h2&gt;How do you get to Mars?&lt;/h2&gt;
  1793.  
  1794. &lt;p&gt;To send people to Mars and return them safely to Earth, NASA has developed a new, very powerful launch vehicle called the &lt;a href="https://www.nasa.gov/humans-in-space/space-launch-system/"&gt;Space Launch System&lt;/a&gt; and a new &lt;a href="https://www.nasa.gov/humans-in-space/orion-spacecraft/"&gt;human carrier spacecraft called Orion&lt;/a&gt;. &lt;/p&gt;
  1795.  
  1796. &lt;p&gt;To prepare and train astronauts for living on and exploring Mars, NASA &lt;a href="https://theconversation.com/nasas-artemis-1-mission-to-the-moon-sets-the-stage-for-routine-space-exploration-beyond-earths-orbit-heres-what-to-expect-and-why-its-important-189447"&gt;established a new program to return humans to the Moon&lt;/a&gt;, called the &lt;a href="https://www.nasa.gov/wp-content/uploads/2023/04/green-moon-kyoto.pdf"&gt;Artemis program&lt;/a&gt;. &lt;/p&gt;
  1797.  
  1798. &lt;p&gt;In mythology, &lt;a href="https://theconversation.com/who-is-artemis-nasas-latest-mission-to-the-moon-is-named-after-an-ancient-lunar-goddess-turned-feminist-icon-189504"&gt;Artemis was Apollo’s twin sister&lt;/a&gt;. The Artemis astronauts will live and work on the Moon for months at a time to prepare for living and working on Mars. &lt;/p&gt;
  1799.  
  1800. &lt;figure&gt;
  1801.            &lt;iframe width="440" height="260" src="https://www.youtube.com/embed/_T8cn2J13-4?wmode=transparent&amp;amp;start=0" frameborder="0" allowfullscreen=""&gt;&lt;/iframe&gt;
  1802.            &lt;figcaption&gt;&lt;span class="caption"&gt;The Artemis program plans to return humans to the Moon, in anticipation of eventually sending humans to Mars.&lt;/span&gt;&lt;/figcaption&gt;
  1803.          &lt;/figure&gt;
  1804.  
  1805. &lt;p&gt;&lt;a href="https://www.nasa.gov/mission/artemis-i/"&gt;The Space Launch System and Orion&lt;/a&gt; successfully launched on Nov. 16, 2022, as part of the Artemis I mission. It made the Artemis program’s first uncrewed flight to the Moon, and once there, Orion orbited the Moon for six days, getting as close as 80 miles (129 kilometers) above the surface. &lt;/p&gt;
  1806.  
  1807. &lt;p&gt;Artemis I splashed back down to Earth on Dec. 11, 2022, after its 1.4 million-mile (2.2 million-kilometer) maiden journey. &lt;/p&gt;
  1808.  
  1809. &lt;p&gt;&lt;a href="https://www.nasa.gov/mission/artemis-iii/"&gt;Artemis III&lt;/a&gt;, the first mission to return humans to the lunar surface, is &lt;a href="https://www.lpi.usra.edu/Artemis/"&gt;scheduled for 2026&lt;/a&gt;. The Artemis astronauts will land at the Moon’s south pole, where scientists believe there may be &lt;a href="https://theconversation.com/scientists-suspect-theres-ice-hiding-on-the-moon-and-a-host-of-missions-from-the-us-and-beyond-are-searching-for-it-216060"&gt;large deposits of subsurface water&lt;/a&gt; in the form of ice that astronauts could mine, melt, purify and drink. The Artemis astronauts will set up habitats on the surface of the Moon and spend several months exploring the lunar surface. &lt;/p&gt;
  1810.  
  1811. &lt;p&gt;Since the Moon is a &lt;a href="https://spaceplace.nasa.gov/moon-distance/en/"&gt;mere 240,000 miles (386,000 km) from Earth&lt;/a&gt;, it will act as a training ground for the future human exploration of Mars. While a Mars mission is still many years out, the Artemis program will help NASA develop the capabilities it needs to explore the red planet.&lt;/p&gt;&lt;img src="https://counter.theconversation.com/content/239814/count.gif" alt="The Conversation" width="1" height="1" /&gt;
  1812. &lt;p class="fine-print"&gt;&lt;em&gt;&lt;span&gt;Joel S. Levine receives funding from NASA. I serve as a consultant to NASA&amp;#39;s Engineering and Safety Center (NESC).&lt;/span&gt;&lt;/em&gt;&lt;/p&gt;</content>
  1813.    <summary>Before sending humans to Mars, NASA will first return humans to the Moon’s surface to test its technology and train astronauts.</summary>
  1814.    <author>
  1815.      <name>Joel S. Levine, Research Professor, Department of Applied Science, William &amp; Mary</name>
  1816.      <foaf:homepage rdf:resource="https://theconversation.com/profiles/joel-s-levine-2215651"/>
  1817.    </author>
  1818.    <rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
  1819.  </entry>
  1820.  <entry>
  1821.    <id>tag:theconversation.com,2011:article/240221</id>
  1822.    <published>2024-10-03T23:29:34Z</published>
  1823.    <updated>2024-10-03T23:29:34Z</updated>
  1824.    <link rel="alternate" type="text/html" href="https://theconversation.com/daylight-saving-is-about-to-start-but-why-do-the-days-get-longer-240221"/>
  1825.    <title>Daylight saving is about to start. But why do the days get longer?</title>
  1826.    <content type="html">&lt;figure&gt;&lt;img src="https://images.theconversation.com/files/623212/original/file-20241003-15-gwbojx.jpg?ixlib=rb-4.1.0&amp;amp;rect=17%2C17%2C5800%2C3785&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=496&amp;amp;fit=clip" /&gt;&lt;figcaption&gt;&lt;span class="caption"&gt;&lt;/span&gt; &lt;span class="attribution"&gt;&lt;a class="source" href="https://www.shutterstock.com/image-photo/st-kilda-pier-melbourne-sunset-people-1489065725"&gt;Kasper Lyngby/Shutterstock&lt;/a&gt;&lt;/span&gt;&lt;/figcaption&gt;&lt;/figure&gt;&lt;p&gt;The days are getting longer and in Australia, the switch to daylight saving time is almost upon us (for about 70% of the population, anyway). &lt;/p&gt;
  1827.  
  1828. &lt;p&gt;But why do we have longer days in summer and shorter days in winter? &lt;/p&gt;
  1829.  
  1830. &lt;h2&gt;It’s all about the tilt&lt;/h2&gt;
  1831.  
  1832. &lt;p&gt;Earth goes around the Sun in an almost circular orbit. But not everything is lined up perfectly. Earth’s axis is tilted by 23.44 degrees relative to its orbit around the Sun. &lt;/p&gt;
  1833.  
  1834. &lt;p&gt;Imagine Earth’s orbit as a flat frisbee with the Sun in the middle and Earth as a ball on a stick going around the edge. &lt;/p&gt;
  1835.  
  1836. &lt;figure class="align-center zoomable"&gt;
  1837.            &lt;a href="https://images.theconversation.com/files/623235/original/file-20241003-16-xourdg.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=1000&amp;amp;fit=clip"&gt;&lt;img alt="Diagram of Earth's rotation around the sun." src="https://images.theconversation.com/files/623235/original/file-20241003-16-xourdg.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;fit=clip" srcset="https://images.theconversation.com/files/623235/original/file-20241003-16-xourdg.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=400&amp;amp;fit=crop&amp;amp;dpr=1 600w, https://images.theconversation.com/files/623235/original/file-20241003-16-xourdg.jpg?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=400&amp;amp;fit=crop&amp;amp;dpr=2 1200w, https://images.theconversation.com/files/623235/original/file-20241003-16-xourdg.jpg?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=400&amp;amp;fit=crop&amp;amp;dpr=3 1800w, https://images.theconversation.com/files/623235/original/file-20241003-16-xourdg.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=503&amp;amp;fit=crop&amp;amp;dpr=1 754w, https://images.theconversation.com/files/623235/original/file-20241003-16-xourdg.jpg?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=503&amp;amp;fit=crop&amp;amp;dpr=2 1508w, https://images.theconversation.com/files/623235/original/file-20241003-16-xourdg.jpg?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=503&amp;amp;fit=crop&amp;amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"&gt;&lt;/a&gt;
  1838.            &lt;figcaption&gt;
  1839.              &lt;span class="caption"&gt;Earth goes around the Sun in an almost circular orbit.&lt;/span&gt;
  1840.              &lt;span class="attribution"&gt;&lt;a class="source" href="https://www.shutterstock.com/image-vector/earths-orbit-earth-rotation-around-sun-2441275921"&gt;Angela Cini/Shutterstock&lt;/a&gt;&lt;/span&gt;
  1841.            &lt;/figcaption&gt;
  1842.          &lt;/figure&gt;
  1843.  
  1844. &lt;p&gt;If Earth’s axis wasn’t tilted (if its tilt was zero degrees) the stick would be exactly perpendicular to the frisbee. If you grab that perpendicular stick and tip it 23.44 degrees sideways, that’s what Earth’s tilt looks like now. &lt;/p&gt;
  1845.  
  1846. &lt;p&gt;As Earth orbits the Sun, the tilt of the stick does not rotate relative to the Sun. If you were in outer space looking at the Sun and you watched from the exact same position for a whole year, you would see Earth go around the Sun while the stick stayed tilted the same direction. &lt;/p&gt;
  1847.  
  1848. &lt;p&gt;In other words, if the top of the stick was pointing to the right when you started watching Earth go around the Sun, it would stay pointing to the right the whole way around.&lt;/p&gt;
  1849.  
  1850.  
  1851.  
  1852. &lt;p&gt;This tilt gives us longer days in summer and shorter days in winter. Let’s set up the scenario so the Northern Hemisphere is the top of the planet and the Southern Hemisphere is the bottom of the planet. &lt;/p&gt;
  1853.  
  1854. &lt;p&gt;When Earth is on one side of the Sun, the top of the stick is pointed towards the Sun. This is summer in the Northern Hemisphere and winter in the Southern Hemisphere. Six months later, when Earth is on the other side of the Sun, the bottom of the stick is pointed towards the Sun – and the seasons are reversed.&lt;/p&gt;
  1855.  
  1856.  
  1857.  
  1858. &lt;h2&gt;Solstices and equinoxes&lt;/h2&gt;
  1859.  
  1860. &lt;p&gt;Those two points, when the top of the stick is pointing directly towards the Sun or directly away from the Sun, are the solstices. They are the longest and shortest days of the year, depending on your hemisphere. &lt;/p&gt;
  1861.  
  1862. &lt;p&gt;The shortest day of 2024 in Australia was June 21. Looking forward to sunnier times, the longest day of the year in 2024 will be December 21.&lt;/p&gt;
  1863.  
  1864.  
  1865.  
  1866. &lt;p&gt;In between the summer and winter solstice, we have the equinoxes – when days and nights are almost exactly the same length. Those are the days when the stick through Earth is “side-on” to the Sun. The equinox is also the day when the Sun passes directly over Earth’s equator. In 2024 this happened on March 20 at 2:06pm AEDT and September 22 at 10:43pm AEST. &lt;/p&gt;
  1867.  
  1868. &lt;p&gt;That means that since September 22, days have been getting longer than nights in the Southern Hemisphere. &lt;/p&gt;
  1869.  
  1870. &lt;h2&gt;What does daylight saving do?&lt;/h2&gt;
  1871.  
  1872. &lt;p&gt;Earth’s tilt means the Sun both rises earlier and sets later as we head towards summer. When the clocks (in some states) switch to daylight saving time, people in these states all get one hour less of sleep. However, the total length of the day doesn’t change just because we changed our clocks. &lt;/p&gt;
  1873.  
  1874. &lt;p&gt;For me, daylight saving means I need an extra cup of coffee in the morning for about a week before I adjust to the daylight saving-lag (like jet lag, but without the fun of travel). &lt;/p&gt;
  1875.  
  1876. &lt;p&gt;What it really gives us is more daylight in the evening, instead of more daylight in the morning. If you’re already a morning person, this isn’t the way to go. But if you prefer to have a long dinner in the summer sun it’s ideal.&lt;/p&gt;
  1877.  
  1878. &lt;h2&gt;Has it always been this way?&lt;/h2&gt;
  1879.  
  1880. &lt;p&gt;Earth’s axis hasn’t always been tilted at 23.44 degrees. It cycles from a minimum 22.1 degree tilt to a maximum 24.5 degree tilt and back again once every approximately 41,000 years. &lt;/p&gt;
  1881.  
  1882. &lt;p&gt;Earth’s axis also “precesses”, where the stick through it draws a circle once every approximately 26,000 years. You can see this in the animation below.&lt;/p&gt;
  1883.  
  1884. &lt;figure class="align-center zoomable"&gt;
  1885.            &lt;a href="https://images.theconversation.com/files/622704/original/file-20241001-16-lh8pl9.gif?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=1000&amp;amp;fit=clip"&gt;&lt;img alt="A gif of the Earth wobbling in a circle on its axis." src="https://images.theconversation.com/files/622704/original/file-20241001-16-lh8pl9.gif?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;fit=clip" srcset="https://images.theconversation.com/files/622704/original/file-20241001-16-lh8pl9.gif?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=600&amp;amp;fit=crop&amp;amp;dpr=1 600w, https://images.theconversation.com/files/622704/original/file-20241001-16-lh8pl9.gif?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=600&amp;amp;fit=crop&amp;amp;dpr=2 1200w, https://images.theconversation.com/files/622704/original/file-20241001-16-lh8pl9.gif?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=600&amp;amp;fit=crop&amp;amp;dpr=3 1800w, https://images.theconversation.com/files/622704/original/file-20241001-16-lh8pl9.gif?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=754&amp;amp;fit=crop&amp;amp;dpr=1 754w, https://images.theconversation.com/files/622704/original/file-20241001-16-lh8pl9.gif?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=754&amp;amp;fit=crop&amp;amp;dpr=2 1508w, https://images.theconversation.com/files/622704/original/file-20241001-16-lh8pl9.gif?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=754&amp;amp;fit=crop&amp;amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"&gt;&lt;/a&gt;
  1886.            &lt;figcaption&gt;
  1887.              &lt;span class="caption"&gt;Demonstration of the precession of Earth’s axis.&lt;/span&gt;
  1888.              &lt;span class="attribution"&gt;&lt;a class="source" href="https://science.nasa.gov/resource/axial-precession-wobble/"&gt;NASA/JPL-Caltech&lt;/a&gt;&lt;/span&gt;
  1889.            &lt;/figcaption&gt;
  1890.          &lt;/figure&gt;
  1891.  
  1892. &lt;p&gt;The length of a day on Earth hasn’t always been the same, either. &lt;/p&gt;
  1893.  
  1894. &lt;p&gt;At the moment, the length of a day is nearly exactly 24 hours. But it’s shifting all the time by tiny amounts. This is tracked very closely by a system of telescopes and satellites. These systems measure “&lt;a href="https://ggos.org/item/earth-orientation-parameter/#:%7E:text=Accordingly%2C%20the%20EOP%20describe%20the,as%20tides%20and%20continental%20drift"&gt;Earth orientation parameters&lt;/a&gt;” that describe Earth’s exact orientation compared to the position of stars in the sky. &lt;/p&gt;
  1895.  
  1896. &lt;p&gt;These are important to astronomers because the exact location of our telescopes is important for creating accurate maps of the sky. On top of all of this, the gravitational drag from the Moon causes days to become longer by around 2.3 milliseconds every 100 years. A few billion years ago, Earth’s day was a lot shorter – &lt;a href="https://www.earthscope.org/news/a-day-is-not-always-24-hours-how-earths-shifting-systems-cause-day-length-variation/#:%7E:text=Billions%20of%20years%20ago%2C%20the,to%20the%20day%20every%20century"&gt;only 19 hours long&lt;/a&gt;.&lt;/p&gt;
  1897.  
  1898. &lt;p&gt;Even though some of us are losing an hour of sleep this weekend, at least we get to enjoy 2.3 milliseconds longer every day than our great – and great-great – grandparents did.&lt;/p&gt;&lt;img src="https://counter.theconversation.com/content/240221/count.gif" alt="The Conversation" width="1" height="1" /&gt;
  1899. &lt;p class="fine-print"&gt;&lt;em&gt;&lt;span&gt;Laura Nicole Driessen is a brand ambassador for the Rise &amp;amp; Shine Education Orbit Centre of Imagination.&lt;/span&gt;&lt;/em&gt;&lt;/p&gt;</content>
  1900.    <summary>Earth’s tilt means the Sun both rises earlier and sets later as we head towards summer.</summary>
  1901.    <author>
  1902.      <name>Laura Nicole Driessen, Postdoctoral researcher in radio astronomy, University of Sydney</name>
  1903.      <foaf:homepage rdf:resource="https://theconversation.com/profiles/laura-nicole-driessen-892965"/>
  1904.    </author>
  1905.    <rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
  1906.  </entry>
  1907.  <entry>
  1908.    <id>tag:theconversation.com,2011:article/237416</id>
  1909.    <published>2024-10-03T16:46:31Z</published>
  1910.    <updated>2024-10-03T16:46:31Z</updated>
  1911.    <link rel="alternate" type="text/html" href="https://theconversation.com/the-earliest-galaxies-formed-amazingly-fast-after-the-big-bang-do-they-break-the-universe-or-change-its-age-237416"/>
  1912.    <title>The earliest galaxies formed amazingly fast after the Big Bang. Do they break the universe or change its age?</title>
  1913.    <content type="html">&lt;figure&gt;&lt;img src="https://images.theconversation.com/files/621105/original/file-20240923-17-9bzk3p.jpg?ixlib=rb-4.1.0&amp;amp;rect=0%2C0%2C3662%2C2092&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=496&amp;amp;fit=clip" /&gt;&lt;figcaption&gt;&lt;span class="caption"&gt;Illustration of the James Webb Space Telescope (JWST).&lt;/span&gt; &lt;span class="attribution"&gt;&lt;a class="source" href="https://www.shutterstock.com/image-photo/jwst-space-galaxy-exploration-james-webb-2182045041"&gt;Dima Zel / Shutterstock&lt;/a&gt;&lt;/span&gt;&lt;/figcaption&gt;&lt;/figure&gt;&lt;p&gt;The &lt;a href="https://webbtelescope.org/home"&gt;James Webb Space Telescope (JWST)&lt;/a&gt; is the largest and most powerful space telescope built to date. Since it was launched in December 2021 it has provided groundbreaking insights. These include discovering the &lt;a href="https://www.cam.ac.uk/research/news/earliest-most-distant-galaxy-discovered-with-james-webb-space-telescope"&gt;earliest and most distant known galaxies&lt;/a&gt;, which existed just 300 million years after the Big Bang.&lt;/p&gt;
  1914.  
  1915. &lt;p&gt;Distant objects are also very ancient because it takes a long time for the light from these objects to reach telescopes. JWST has now found a number of these very early galaxies. We’re effectively looking back in time at these objects, seeing them as they looked shortly after the birth of the universe. &lt;/p&gt;
  1916.  
  1917. &lt;p&gt;These observations from JWST agree with our current understanding of cosmology – the scientific discipline that aims to explain the universe – and of galaxy formation. But they also reveal aspects we didn’t expect. Many of these early galaxies &lt;a href="https://www.nature.com/articles/s41550-023-01918-w"&gt;shine much more brightly&lt;/a&gt; than we would expect given that they existed just a short time after the Big Bang. &lt;/p&gt;
  1918.  
  1919. &lt;p&gt;Brighter galaxies are thought to have more stars and more mass. It was thought that much more time was needed for this level of star formation to take place. These galaxies also have actively growing black holes at their centres – a sign that these objects matured quickly after the Big Bang. So how can we explain these surprising findings? Do they break our ideas of cosmology or require a change to the age of the universe?&lt;/p&gt;
  1920.  
  1921. &lt;hr&gt;
  1922.  
  1923.  
  1924.  
  1925. &lt;p&gt;&lt;em&gt;This is article is part of our series &lt;a href="https://theconversation.com/uk/topics/cosmology-in-crisis-163581"&gt;Cosmology in crisis?&lt;/a&gt; which uncovers the greatest problems facing cosmologists today – and discusses the implications of solving them.&lt;/em&gt;&lt;/p&gt;
  1926.  
  1927. &lt;hr&gt;
  1928.  
  1929. &lt;p&gt;Scientists have been able to study these early galaxies by combining JWST’s detailed images with its powerful capabilities for spectroscopy. Spectroscopy is a method for interpreting the electromagnetic radiation that’s emitted or absorbed by objects in space. This in turn can tell you about the properties of an object.&lt;/p&gt;
  1930.  
  1931. &lt;p&gt;Our understanding of cosmology and galaxy formation rests on a few fundamental ideas. One of these is the cosmological principle, which states that, on a large scale, the universe is homogeneous (the same everywhere) and isotropic (the same in all directions). Combined with Einstein’s &lt;a href="https://www.britannica.com/science/general-relativity"&gt;theory of general relativity&lt;/a&gt;, this principle allows us to connect the evolution of the universe –- how it expands or contracts –- to its energy and mass content.&lt;/p&gt;
  1932.  
  1933. &lt;p&gt;The standard cosmological model, known as the “Hot Big Bang” theory, includes three main components, or ingredients. One is the ordinary matter that we can see with our eyes in galaxies, stars and planets. A second ingredient is cold dark matter (CDM), slow-moving matter particles that do not emit, absorb or reflect light. &lt;/p&gt;
  1934.  
  1935. &lt;p&gt;The third component is what’s known the cosmological constant (Λ, or lambda). This is linked to something called dark energy and is a way of explaining the fact that the &lt;a href="https://iopscience.iop.org/article/10.1086/300499"&gt;expansion of the universe is accelerating&lt;/a&gt;. Together, these components form what is called the &lt;a href="https://lambda.gsfc.nasa.gov/education/graphic_history/univ_evol.html"&gt;ΛCDM model&lt;/a&gt; of cosmology.&lt;/p&gt;
  1936.  
  1937. &lt;figure class="align-center "&gt;
  1938.            &lt;img alt="JADES-GS-z14-0" src="https://images.theconversation.com/files/615411/original/file-20240824-18-8uegg0.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;fit=clip" srcset="https://images.theconversation.com/files/615411/original/file-20240824-18-8uegg0.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=434&amp;amp;fit=crop&amp;amp;dpr=1 600w, https://images.theconversation.com/files/615411/original/file-20240824-18-8uegg0.jpg?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=434&amp;amp;fit=crop&amp;amp;dpr=2 1200w, https://images.theconversation.com/files/615411/original/file-20240824-18-8uegg0.jpg?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=434&amp;amp;fit=crop&amp;amp;dpr=3 1800w, https://images.theconversation.com/files/615411/original/file-20240824-18-8uegg0.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=546&amp;amp;fit=crop&amp;amp;dpr=1 754w, https://images.theconversation.com/files/615411/original/file-20240824-18-8uegg0.jpg?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=546&amp;amp;fit=crop&amp;amp;dpr=2 1508w, https://images.theconversation.com/files/615411/original/file-20240824-18-8uegg0.jpg?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=546&amp;amp;fit=crop&amp;amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"&gt;
  1939.            &lt;figcaption&gt;
  1940.              &lt;span class="caption"&gt;JADES-GS-z14-0 is the current record-holder for the most distant known galaxy. This image captures it at a time less than 300 million years after the Big Bang.&lt;/span&gt;
  1941.              &lt;span class="attribution"&gt;&lt;a class="source" href="https://webbtelescope.org/contents/media/images/01HZ083EXXCJNE64ERAH2ER2FM"&gt;NASA, ESA, CSA, STScI, Brant Robertson (UC Santa Cruz), Ben Johnson (CfA), Sandro Tacchella (Cambridge), Phill Cargile (CfA) and the JADES collaboration.&lt;/a&gt;&lt;/span&gt;
  1942.            &lt;/figcaption&gt;
  1943.          &lt;/figure&gt;
  1944.  
  1945. &lt;p&gt;&lt;a href="https://science.nasa.gov/universe/the-universe-is-expanding-faster-these-days-and-dark-energy-is-responsible-so-what-is-dark-energy/"&gt;Dark energy&lt;/a&gt; makes up about 68% of the total energy content of today’s universe.&lt;/p&gt;
  1946.  
  1947. &lt;p&gt;Despite not being directly observable with scientific instruments, dark matter is thought to make up most of the matter in the cosmos and comprises about 27% of the universe’s total mass and energy content.&lt;/p&gt;
  1948.  
  1949. &lt;p&gt;While dark matter and dark energy remain mysterious, the ΛCDM model of cosmology
  1950. is supported by a wide range of detailed observations. These include the
  1951. measurement of the universe’s expansion, the &lt;a href="https://www.esa.int/Science_Exploration/Space_Science/Cosmic_Microwave_Background_CMB_radiation"&gt;cosmic microwave background, or CMB&lt;/a&gt; (the “afterglow” of the Big Bang) and the development of galaxies and their large-scale distribution – for example, the way that galaxies cluster together. &lt;/p&gt;
  1952.  
  1953. &lt;p&gt;The ΛCDM model lays the groundwork for our understanding of how galaxies form and evolve. For example, the CMB, which was emitted about 380,000 years after &lt;a href="https://www.iop.org/explore-physics/big-ideas-physics/big-bang"&gt;the Big Bang&lt;/a&gt;, provides a snapshot of early fluctuations in density that occurred in the early universe. These fluctuations, particularly in dark matter, eventually developed into the structures we observe today, such as galaxies and stars.&lt;/p&gt;
  1954.  
  1955.  
  1956.  
  1957. &lt;h2&gt;How stars form&lt;/h2&gt;
  1958.  
  1959. &lt;p&gt;Galaxy formation consists of complex processes influenced by numerous different physical phenomena. Some of these mechanisms are not fully understood, such as what processes govern how gas in galaxies cools and condenses to form stars. &lt;/p&gt;
  1960.  
  1961. &lt;p&gt;The effects of supernovae, stellar winds and black holes that emit significant amounts of energy (sometimes called &lt;a href="https://webbtelescope.org/contents/articles/what-are-active-galactic-nuclei"&gt;active galactic nuclei, or AGN)&lt;/a&gt; can all heat or expel gas from galaxies. This in turn can boost or curtail star formation and therefore influence the growth of galaxies. &lt;/p&gt;
  1962.  
  1963. &lt;hr&gt;
  1964. &lt;p&gt;
  1965.  &lt;em&gt;
  1966.    &lt;strong&gt;
  1967.      Read more:
  1968.      &lt;a href="https://theconversation.com/cosmology-in-crisis-a-new-series-from-the-conversation-238811"&gt;Cosmology in crisis? A new series from The Conversation&lt;/a&gt;
  1969.    &lt;/strong&gt;
  1970.  &lt;/em&gt;
  1971. &lt;/p&gt;
  1972. &lt;hr&gt;
  1973.  
  1974.  
  1975. &lt;hr&gt;
  1976. &lt;p&gt;
  1977.  &lt;em&gt;
  1978.    &lt;strong&gt;
  1979.      Read more:
  1980.      &lt;a href="https://theconversation.com/cosmology-is-at-a-tipping-point-we-may-be-on-the-verge-of-discovering-new-physics-237695"&gt;Cosmology is at a tipping point – we may be on the verge of discovering new physics&lt;/a&gt;
  1981.    &lt;/strong&gt;
  1982.  &lt;/em&gt;
  1983. &lt;/p&gt;
  1984. &lt;hr&gt;
  1985.  
  1986.  
  1987. &lt;p&gt;The efficiency and scale of these “feedback processes”, as well as their cumulative impact over time, are poorly understood. They are a significant source of uncertainty in mathematical models, or simulations, of galaxy formation. &lt;/p&gt;
  1988.  
  1989. &lt;p&gt;Significant advances in complex numerical simulations of galaxy formation have been made over the past ten years. Insights and hints can still be gained from simpler simulations and models that relate star formation to the evolution of dark matter halos. These halos are massive, invisible structures made from dark matter that effectively anchor galaxies within them.&lt;/p&gt;
  1990.  
  1991. &lt;figure class="align-center "&gt;
  1992.            &lt;img alt="Active galactic nucleus." src="https://images.theconversation.com/files/621108/original/file-20240923-17-j0fp3q.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;fit=clip" srcset="https://images.theconversation.com/files/621108/original/file-20240923-17-j0fp3q.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=338&amp;amp;fit=crop&amp;amp;dpr=1 600w, https://images.theconversation.com/files/621108/original/file-20240923-17-j0fp3q.jpg?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=338&amp;amp;fit=crop&amp;amp;dpr=2 1200w, https://images.theconversation.com/files/621108/original/file-20240923-17-j0fp3q.jpg?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=338&amp;amp;fit=crop&amp;amp;dpr=3 1800w, https://images.theconversation.com/files/621108/original/file-20240923-17-j0fp3q.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=424&amp;amp;fit=crop&amp;amp;dpr=1 754w, https://images.theconversation.com/files/621108/original/file-20240923-17-j0fp3q.jpg?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=424&amp;amp;fit=crop&amp;amp;dpr=2 1508w, https://images.theconversation.com/files/621108/original/file-20240923-17-j0fp3q.jpg?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=424&amp;amp;fit=crop&amp;amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"&gt;
  1993.            &lt;figcaption&gt;
  1994.              &lt;span class="caption"&gt;Active galactic nuclei are among the phenomena that may have influenced star formation in galaxies.&lt;/span&gt;
  1995.              &lt;span class="attribution"&gt;&lt;a class="source" href="https://svs.gsfc.nasa.gov/20135/"&gt;NASA/Goddard Space Flight Center Conceptual Image Lab.&lt;/a&gt;&lt;/span&gt;
  1996.            &lt;/figcaption&gt;
  1997.          &lt;/figure&gt;
  1998.  
  1999. &lt;p&gt;One of the simpler models of galaxy formation assumes that the rate at which stars form in a galaxy is directly tied to gas flowing into those galaxies. This model also proposes that the star formation rate in a galaxy is proportional to the rate at which dark matter halos grow. It assumes a fixed efficiency at converting gas into stars, regardless of cosmic time.&lt;/p&gt;
  2000.  
  2001. &lt;p&gt;This &lt;a href="https://iopscience.iop.org/article/10.3847/1538-4357/aae8e0"&gt;“constant star formation efficiency” model&lt;/a&gt; is consistent with star formation increasing dramatically in the first billion years after the Big Bang. The rapid growth of dark matter halos during this period would have provided the necessary conditions for galaxies to form stars efficiently. Despite its simplicity, this model has successfully predicted a wide range of real observations, including the overall rate of star formation across cosmic time.&lt;/p&gt;
  2002.  
  2003. &lt;h2&gt;Secrets of the first galaxies&lt;/h2&gt;
  2004.  
  2005. &lt;p&gt;JWST has ushered in a new era of discovery. With its advanced instruments, the space telescope can capture both detailed images and high resolution spectra – charts showing the intensity of electromagnetic radiation emitted or absorbed by objects in the sky. For JWST, these spectra are in the near infrared region of the electromagnetic spectrum. Studying this region is crucial for observing early galaxies whose optical light has turned into near infrared (or “redshifted”) as the universe has expanded.&lt;/p&gt;
  2006.  
  2007. &lt;p&gt;Redshift describes how the wavelengths of light from galaxies become stretched as they travel. The more distant a galaxy is, the greater its redshift.&lt;/p&gt;
  2008.  
  2009. &lt;figure class="align-center "&gt;
  2010.            &lt;img alt="JADES deep field" src="https://images.theconversation.com/files/615983/original/file-20240828-16-pdha26.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;fit=clip" srcset="https://images.theconversation.com/files/615983/original/file-20240828-16-pdha26.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=382&amp;amp;fit=crop&amp;amp;dpr=1 600w, https://images.theconversation.com/files/615983/original/file-20240828-16-pdha26.jpg?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=382&amp;amp;fit=crop&amp;amp;dpr=2 1200w, https://images.theconversation.com/files/615983/original/file-20240828-16-pdha26.jpg?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=382&amp;amp;fit=crop&amp;amp;dpr=3 1800w, https://images.theconversation.com/files/615983/original/file-20240828-16-pdha26.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=480&amp;amp;fit=crop&amp;amp;dpr=1 754w, https://images.theconversation.com/files/615983/original/file-20240828-16-pdha26.jpg?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=480&amp;amp;fit=crop&amp;amp;dpr=2 1508w, https://images.theconversation.com/files/615983/original/file-20240828-16-pdha26.jpg?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=480&amp;amp;fit=crop&amp;amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"&gt;
  2011.            &lt;figcaption&gt;
  2012.              &lt;span class="caption"&gt;A deep field image using JWST. These are long-lasting observations of a particular region of the sky intended to reveal faint objects.&lt;/span&gt;
  2013.              &lt;span class="attribution"&gt;&lt;a class="source" href="https://webbtelescope.org/contents/media/images/01GKT0RRJBP5ZMJRMCQNPT8SXP"&gt;NASA, ESA, CSA, STScI, Brant Robertson (UC Santa Cruz), Ben Johnson (CfA), Sandro Tacchella (Cambridge), Phill Cargile (CfA) and the JADES collaboration.&lt;/a&gt;&lt;/span&gt;
  2014.            &lt;/figcaption&gt;
  2015.          &lt;/figure&gt;
  2016.  
  2017. &lt;p&gt;Over the past two years, JWST has identified and characterised galaxies at redshifts with values of between ten and 15. These &lt;a href="https://www.nature.com/articles/s41550-023-01921-1"&gt;galaxies&lt;/a&gt;, which formed around 200-500 million years after the Big Bang, are relatively small for galaxies (about 100 parsecs, or 3 quadrillion kilometres, across). They each consist of around 100 million stars, and form new stars at a rate of about one sun-like star per year. &lt;/p&gt;
  2018.  
  2019. &lt;p&gt;While this does not sound very impressive, it implies that these systems double their content of stars within only 100 million years. For comparison, our own Milky Way galaxy takes about 25 billion years to double its stellar mass.&lt;/p&gt;
  2020.  
  2021. &lt;hr&gt;
  2022. &lt;p&gt;
  2023.  &lt;em&gt;
  2024.    &lt;strong&gt;
  2025.      Read more:
  2026.      &lt;a href="https://theconversation.com/astronomers-cant-agree-on-how-fast-the-universe-is-expanding-new-approaches-are-aiming-to-break-the-impasse-236985"&gt;Astronomers can't agree on how fast the universe is expanding. New approaches are aiming to break the impasse&lt;/a&gt;
  2027.    &lt;/strong&gt;
  2028.  &lt;/em&gt;
  2029. &lt;/p&gt;
  2030. &lt;hr&gt;
  2031.  
  2032.  
  2033. &lt;hr&gt;
  2034. &lt;p&gt;
  2035.  &lt;em&gt;
  2036.    &lt;strong&gt;
  2037.      Read more:
  2038.      &lt;a href="https://theconversation.com/the-universe-is-smoother-than-the-standard-model-of-cosmology-suggests-so-is-the-theory-broken-238098"&gt;The universe is smoother than the standard model of cosmology suggests – so is the theory broken?&lt;/a&gt;
  2039.    &lt;/strong&gt;
  2040.  &lt;/em&gt;
  2041. &lt;/p&gt;
  2042. &lt;hr&gt;
  2043.  
  2044.  
  2045. &lt;h2&gt;Early galaxy formation&lt;/h2&gt;
  2046.  
  2047. &lt;p&gt;The surprising findings from JWST of bright galaxies at high redshifts, or distances, could imply that these galaxies matured faster than expected after the Big Bang. This is important because it would challenge existing models of galaxy formation. The constant star-formation efficiency model described above, while effective at explaining much of what we see, struggles to account for the large number of bright and distant galaxies observed with a redshift of more than ten with a redshift of more than ten.&lt;/p&gt;
  2048.  
  2049. &lt;p&gt;To address this, scientists are exploring various possibilities. These include changes to their theories of how efficiently gas is converted into stars over time. They are also reconsidering the relative importance of the feedback processes – how phenomena such as supernovae and black holes also help regulate star formation. &lt;/p&gt;
  2050.  
  2051. &lt;p&gt;Some theories suggest that star formation in the early universe may have been more intense or “bursty” than previously thought, leading to the &lt;a href="https://news.northwestern.edu/stories/2023/09/bursts-of-star-formation-explain-mysterious-brightness-at-cosmic-dawn/"&gt;rapid growth&lt;/a&gt; of these early galaxies and their apparent brightness.&lt;/p&gt;
  2052.  
  2053.  
  2054.  
  2055. &lt;p&gt;Others propose that different factors, such as lower amounts of galactic dust, a top-heavy distribution of star masses, or contributions from phenomena such as active black holes, could be responsible for the unexpected brightness of these early galaxies.&lt;/p&gt;
  2056.  
  2057. &lt;p&gt;These explanations invoke changes to galaxy formation physics in order to explain JWST’s findings. But scientists have also been considering modifications to broad cosmological theories. For example, the abundance of early, bright galaxies could be partly explained by a change to something called the matter power spectrum. This is a way to describe density differences in the universe.&lt;/p&gt;
  2058.  
  2059. &lt;p&gt;One possible mechanism for achieving this change in the matter power spectrum is a theoretical phenomenon called &lt;a href="https://www.phy.cam.ac.uk/news/dark-energy-early-universe-could-solve-two-major-problems-cosmology"&gt;“early dark energy”&lt;/a&gt;. This is the idea that a new cosmological energy source with similarities to dark energy may have existed at early times, at a redshift of 3,000. This is before the CMB was emitted and just 380,000 years after the Big Bang. &lt;/p&gt;
  2060.  
  2061. &lt;p&gt;This early dark energy would have decayed rapidly after the stage of the universe’s evolution known as recombination. Intriguingly, early dark energy could also alleviate &lt;a href="https://theconversation.com/astronomers-cant-agree-on-how-fast-the-universe-is-expanding-new-approaches-are-aiming-to-break-the-impasse-236985"&gt;the Hubble tension&lt;/a&gt; –- a discrepancy between different estimates of the &lt;a href="https://www.space.com/space-exploration/james-webb-space-telescope/the-james-webb-space-telescope-has-solved-a-lot-of-puzzles-and-created-a-few-more"&gt;universe’s age&lt;/a&gt;. &lt;/p&gt;
  2062.  
  2063. &lt;p&gt;&lt;a href="https://academic.oup.com/mnras/article/524/3/3385/7221343"&gt;One paper published in 2023&lt;/a&gt; suggested that the galaxy findings from JWST required scientists to stretch the age of the universe by several billion years. &lt;/p&gt;
  2064.  
  2065. &lt;p&gt;However, other phenomena could account for the bright galaxies. Before JWST’s observations are used to invoke changes to broad ideas of cosmology, a more detailed understanding of the physical processes in galaxies is essential.&lt;/p&gt;
  2066.  
  2067. &lt;p&gt;The current record holder for the most distant galaxy – identified by JWST – is &lt;a href="https://www.nature.com/articles/s41586-024-07860-9"&gt;called JADES-GS-z14-0&lt;/a&gt;. The data gathered so far indicate that these galaxies have a large diversity of different properties.&lt;/p&gt;
  2068.  
  2069. &lt;figure&gt;
  2070.            &lt;iframe width="440" height="260" src="https://www.youtube.com/embed/6NKbDrXua4k?wmode=transparent&amp;amp;start=0" frameborder="0" allowfullscreen=""&gt;&lt;/iframe&gt;
  2071.            &lt;figcaption&gt;&lt;span class="caption"&gt;3D visualisation of galaxies observed by the JWST, including JADES-GS-z14-0.&lt;/span&gt;&lt;/figcaption&gt;
  2072.          &lt;/figure&gt;
  2073.  
  2074. &lt;p&gt;Some galaxies show signs of hosting black holes that are emitting energy, while others seem to be consistent with hosting young, dust-free populations of stars. Because these galaxies are faint and observing them is expensive (it takes exposure times of many hours), only 20 galaxies for which the redshift is more than ten have been observed with spectroscopy to date, and it will take years to build a statistical sample.&lt;/p&gt;
  2075.  
  2076. &lt;p&gt;A different angle of attack could be observations of galaxies at later cosmic
  2077. times, when the universe was 1 billion to 2 billion years old (redshifts of between three and nine). JWST’s capabilities give researchers access to crucial indicators from stars and gas in these objects that can be used to constrain the overall history of galaxy formation. &lt;/p&gt;
  2078.  
  2079. &lt;h2&gt;Breaking the universe?&lt;/h2&gt;
  2080.  
  2081. &lt;p&gt;In the first year of JWST’s operation, it was claimed that some of the earliest galaxies had extremely high stellar masses (the masses of stars contained within them) and a change in cosmology was needed to accommodate bright galaxies that existed in the very early universe. They were even dubbed &lt;a href="https://www.skyatnightmagazine.com/space-science/webb-telescope-universe-breaker-galaxies"&gt;“universe-breaker” galaxies&lt;/a&gt;. &lt;/p&gt;
  2082.  
  2083. &lt;p&gt;Soon after, it was clear that these galaxies do not break the universe, but their properties can be explained by a range of different phenomena. Better observational data showed that the distances to some of the objects were overestimated (which led to an overestimation of their stellar masses). &lt;/p&gt;
  2084.  
  2085. &lt;p&gt;The emission of light from these galaxies can be powered by sources other than stars, such as accreting black holes. Assumptions in models or simulations can also lead to biases in the total mass of stars in these galaxies. &lt;/p&gt;
  2086.  
  2087. &lt;p&gt;As JWST continues its mission, it will help scientists refine their models and answer some of the most fundamental questions about our cosmic origins. It should unlock even more secrets about the universe’s earliest days, including the puzzle of these bright, distant galaxies.&lt;/p&gt;&lt;img src="https://counter.theconversation.com/content/237416/count.gif" alt="The Conversation" width="1" height="1" /&gt;
  2088. &lt;p class="fine-print"&gt;&lt;em&gt;&lt;span&gt;Sandro Tacchella does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.&lt;/span&gt;&lt;/em&gt;&lt;/p&gt;</content>
  2089.    <summary>Some of the earliest galaxies found with JWST are also the brightest. That’s a problem for our ideas about the universe.</summary>
  2090.    <author>
  2091.      <name>Sandro Tacchella, Assistant Professor in Astrophysics, Kavli Institute for Cosmology, Cambridge, Department of Physics, University of Cambridge</name>
  2092.      <foaf:homepage rdf:resource="https://theconversation.com/profiles/sandro-tacchella-2218123"/>
  2093.    </author>
  2094.    <rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
  2095.  </entry>
  2096.  <entry>
  2097.    <id>tag:theconversation.com,2011:article/240394</id>
  2098.    <published>2024-10-03T14:46:33Z</published>
  2099.    <updated>2024-10-03T14:46:33Z</updated>
  2100.    <link rel="alternate" type="text/html" href="https://theconversation.com/the-esas-hera-mission-takes-flight-toward-the-asteroid-deflected-by-nasas-dart-probe-two-years-ago-240394"/>
  2101.    <title>The ESA’s Hera mission takes flight toward the asteroid deflected by NASA’s DART probe two years ago</title>
  2102.    <content type="html">&lt;figure&gt;&lt;img src="https://images.theconversation.com/files/623114/original/file-20241001-20-7mf853.jpg?ixlib=rb-4.1.0&amp;amp;rect=11%2C11%2C2485%2C1392&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=496&amp;amp;fit=clip" /&gt;&lt;figcaption&gt;&lt;span class="caption"&gt;Hera and its two CubeSats are leaving Earth on October 7th.&lt;/span&gt; &lt;span class="attribution"&gt;&lt;a class="source" href="https://www.esa.int/ESA_Multimedia/Images/2024/01/Hera_heads_into_space"&gt;ESA&lt;/a&gt;, &lt;a class="license" href="http://creativecommons.org/licenses/by/4.0/"&gt;CC BY&lt;/a&gt;&lt;/span&gt;&lt;/figcaption&gt;&lt;/figure&gt;&lt;p&gt;The European Space Agency’s Hera mission will set off from Cape Canaveral on 7 October on a SpaceX Falcon 9 rocket. It will travel several hundred million kilometres to reach the double asteroid Didymos in autumn 2026.&lt;/p&gt;
  2103.  
  2104. &lt;p&gt;This is the follow-up of the intentional impact of NASA’s DART probe onto the smaller body of this double asteroid, the moon called Dimorphos. This first-ever asteroid deflection test aims at modifying the trajectory of the target and understanding precisely what went on. And we already know quite a few things about the success of this deflection – thanks to a camera on-board DART, an Italian minisatellite (or CubeSat) deployed before impact, the combined power of ground-based telescopes, and the sharp eyes of Hubble and James Webb Space Telescope (JWST).&lt;/p&gt;
  2105.  
  2106. &lt;figure&gt;
  2107.            &lt;iframe width="440" height="260" src="https://www.youtube.com/embed/N-OvnVdZP_8?wmode=transparent&amp;amp;start=0" frameborder="0" allowfullscreen=""&gt;&lt;/iframe&gt;
  2108.            &lt;figcaption&gt;&lt;span class="caption"&gt;The images of the collision between the DART probe and Dimorphos were broadcast live right up to the impact on 26 September 2022, giving the public the chance to discover with the scientists what this double asteroid really looked like. The latest image, with a resolution of 5.5 cm, shows a surface filled with rocks up to several metres in size. The probe (1.2 x 1.3 x 1.3 metres for the main structure plus 8.5 metres of solar panels on either side, weighing 580 kilograms) and Dimorphos (151 metres in diameter) were approaching each other at a speed of 6.1 kilometres per second. The collision altered the trajectory of Dimorphos around Didymos. (Johns Hopkins Applied Physics Laboratory).&lt;/span&gt;&lt;/figcaption&gt;
  2109.          &lt;/figure&gt;
  2110.  
  2111. &lt;p&gt;However, we lack a great deal of information to really understand what happened following the impact. This is essential for generalising the results and developing models that would enable us to deflect other asteroids that arrive toward the Earth or space installations (satellites, space stations…).&lt;/p&gt;
  2112.  
  2113. &lt;p&gt;Understanding what Didymos and Dimorphos look like now is Hera’s mission.&lt;/p&gt;
  2114.  
  2115. &lt;h2&gt;What we already know about the deflection&lt;/h2&gt;
  2116.  
  2117. &lt;p&gt;This first-ever asteroid deflection test was a complete success. Firstly, because the DART probe successfully guided itself in the final hours before impact (autonomously) to collide with a small asteroid whose size was the main thing we knew about it.&lt;/p&gt;
  2118.  
  2119. &lt;p&gt;Secondly, because the collision did indeed deflect the trajectory of Dimorphos, as was shown by a campaign of observations by ground-based telescopes, spread out on most continents. Together, they measured the reduction in the orbital period of Dimorphos around Didymos (11.22 hours after impact compared with 11.55 hours before), also demonstrating the ability to organise on an international scale to measure the consequences of a deviation.&lt;/p&gt;
  2120.  
  2121. &lt;p&gt;The images taken by DART before the impact also provided some knowledge of the surface properties of the Dimorphos target and its main body.&lt;/p&gt;
  2122.  
  2123. &lt;p&gt;Finally, images taken by the Italian minisatellite LICIAcube, launched by DART before the impact to observe it from a distance, as well as images from the James Webb and Hubble space telescopes, which were pointing at the same object for the first time, showed that a tail of dust was emitted by the impact. And that this dust spread out over tens of thousands of kilometres afterwards, pushed by the Sun’s light exerting pressure on it (a phenomenon known as ‘solar radiation pressure’). Some of &lt;a href="https://iopscience.iop.org/article/10.3847/PSJ/ad6b0f"&gt;this dust could actually end up in the Earth’s atmosphere as shooting stars&lt;/a&gt; (with no risk of damage as they would burn up completely in the atmosphere).&lt;/p&gt;
  2124.  
  2125. &lt;h2&gt;Hera and her CubeSats, three ultra-sophisticated science detectives&lt;/h2&gt;
  2126.  
  2127. &lt;p&gt;But even all this information is not enough to measure the effectiveness of the asteroid redirection technique and to &lt;a href="https://www.odilejacob.fr/catalogue/sciences/astronomie-astrophysique-cosmologie/a-la-rencontre-des-asteroides_9782415004989.php"&gt;validate our modelling of such impacts&lt;/a&gt; – which must be able to reproduce this test at scale in order to extrapolate it to other scenarios.&lt;/p&gt;
  2128.  
  2129. &lt;p&gt;Crucial questions remain unanswered. For example, to measure the effectiveness of the deflection, we need to know the mass of Dimorphos. To understand how the impact affected the double asteroid system, we need to know more about the physical properties of Dimorphos, and in particular its internal properties: Are there large voids inside Dimorphos, and what are the sizes of the boulders that make it up? Or is it a compact rock covered with surface rocks? Did DART’s impact produce a crater or did it change the shape of the small moon altogether, as &lt;a href="https://doi.org/10.1038/s41550-024-02200-3"&gt;some modelling&lt;/a&gt; predicts and &lt;a href="https://www.nature.com/articles/s41550-024-02200-3"&gt;some recent ground observations&lt;/a&gt; seem to indicate?&lt;/p&gt;
  2130.  
  2131. &lt;figure class="align-center zoomable"&gt;
  2132.            &lt;a href="https://images.theconversation.com/files/622680/original/file-20241001-16-6t26op.jpeg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=1000&amp;amp;fit=clip"&gt;&lt;img alt="The Hera probe and the two mini-satellites around Dimorphos" src="https://images.theconversation.com/files/622680/original/file-20241001-16-6t26op.jpeg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;fit=clip" srcset="https://images.theconversation.com/files/622680/original/file-20241001-16-6t26op.jpeg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=427&amp;amp;fit=crop&amp;amp;dpr=1 600w, https://images.theconversation.com/files/622680/original/file-20241001-16-6t26op.jpeg?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=427&amp;amp;fit=crop&amp;amp;dpr=2 1200w, https://images.theconversation.com/files/622680/original/file-20241001-16-6t26op.jpeg?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=427&amp;amp;fit=crop&amp;amp;dpr=3 1800w, https://images.theconversation.com/files/622680/original/file-20241001-16-6t26op.jpeg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=536&amp;amp;fit=crop&amp;amp;dpr=1 754w, https://images.theconversation.com/files/622680/original/file-20241001-16-6t26op.jpeg?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=536&amp;amp;fit=crop&amp;amp;dpr=2 1508w, https://images.theconversation.com/files/622680/original/file-20241001-16-6t26op.jpeg?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=536&amp;amp;fit=crop&amp;amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"&gt;&lt;/a&gt;
  2133.            &lt;figcaption&gt;
  2134.              &lt;span class="caption"&gt;The two CubeSats will be equipped with a radio satellite link with the Hera probe, which will transmit to Earth, in order to measure the mass and gravity field of the asteroid. The Juventas CubeSat will carry a low-frequency radar that will probe the internal structure of an asteroid for the first time, and a gravimeter that will precisely measure the asteroid’s mass and gravity field. The CubeSat Milani carries an infrared imager to measure the mineralogical properties of Dimorphos, in particular those of the subsurface portions revealed by the DART impact, as well as a dust detector and analyser. This is an artist’s view, where Dimorphos appears larger than Didymos and the impact has been represented by a crater (the existence of which is not yet known).&lt;/span&gt;
  2135.              &lt;span class="attribution"&gt;&lt;a class="source" href="https://www.esa.int/ESA_Multimedia/Images/2024/09/Hera_and_its_CubeSats_connected_by_inter-satellite_links"&gt;ESA&lt;/a&gt;, &lt;a class="license" href="http://creativecommons.org/licenses/by/4.0/"&gt;CC BY&lt;/a&gt;&lt;/span&gt;
  2136.            &lt;/figcaption&gt;
  2137.          &lt;/figure&gt;
  2138.  
  2139. &lt;p&gt;So, like a detective, Hera is now setting off to investigate and report back on exactly what happened and why. And Hera is the hero of this story, as it’s the first time a probe will move so close to a double asteroid.&lt;/p&gt;
  2140.  
  2141. &lt;p&gt;It will also be the first time that a space mission has explored a small body using three satellites at the same time. Hera carries two “CubeSats”, each the size of a shoebox and equipped with its own propulsion systems and a variety of measurement instruments. They’ll be deployed in the vicinity of the asteroid to take measurements at closer range.&lt;/p&gt;
  2142.  
  2143. &lt;p&gt;This configuration is intended to demonstrate the advantages of taking smaller modules on board, enabling us to take greater risks by deploying them for operations at very close range, while the main probe remains at a distance and ensures that the essential scientific objectives are met (the Hera probe itself carries two cameras for observation in the visible range, a hyperspectral imager providing data on mineralogical composition, a thermal infrared imager supplied by the Japanese Space Agency, the JAXA, to determine the thermal properties and roughness of the surface, and a laser altimeter).&lt;/p&gt;
  2144.  
  2145. &lt;p&gt;Before receiving the first images of Dimorphos transformed by this first deflection test, we will have the opportunity to marvel at the probe’s flyby of Mars in mid-March 2025, during which the in-flight instruments will be calibrated by observing not only the planet, but also one of its two moons, Deimos… possibly offering new scientific data on its way.&lt;/p&gt;
  2146.  
  2147. &lt;figure class="align-center zoomable"&gt;
  2148.            &lt;a href="https://images.theconversation.com/files/623000/original/file-20241002-16-u7ms0f.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=1000&amp;amp;fit=clip"&gt;&lt;img alt="Mars and Hera" src="https://images.theconversation.com/files/623000/original/file-20241002-16-u7ms0f.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;fit=clip" srcset="https://images.theconversation.com/files/623000/original/file-20241002-16-u7ms0f.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=337&amp;amp;fit=crop&amp;amp;dpr=1 600w, https://images.theconversation.com/files/623000/original/file-20241002-16-u7ms0f.jpg?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=337&amp;amp;fit=crop&amp;amp;dpr=2 1200w, https://images.theconversation.com/files/623000/original/file-20241002-16-u7ms0f.jpg?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=337&amp;amp;fit=crop&amp;amp;dpr=3 1800w, https://images.theconversation.com/files/623000/original/file-20241002-16-u7ms0f.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=424&amp;amp;fit=crop&amp;amp;dpr=1 754w, https://images.theconversation.com/files/623000/original/file-20241002-16-u7ms0f.jpg?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=424&amp;amp;fit=crop&amp;amp;dpr=2 1508w, https://images.theconversation.com/files/623000/original/file-20241002-16-u7ms0f.jpg?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=424&amp;amp;fit=crop&amp;amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"&gt;&lt;/a&gt;
  2149.            &lt;figcaption&gt;
  2150.              &lt;span class="caption"&gt;Artist’s view of Hera passing close to Mars and its moons, Phobos and Deimos, in March 2025.&lt;/span&gt;
  2151.              &lt;span class="attribution"&gt;&lt;a class="source" href="https://www.esa.int/var/esa/storage/images/esa_multimedia/images/2024/02/hera_s_mars_swingby/25470341-2-eng-GB/Hera_s_Mars_swingby_pillars.png"&gt;ESA&lt;/a&gt;, &lt;a class="license" href="http://creativecommons.org/licenses/by/4.0/"&gt;CC BY&lt;/a&gt;&lt;/span&gt;
  2152.            &lt;/figcaption&gt;
  2153.          &lt;/figure&gt;
  2154.  
  2155. &lt;h2&gt;Studying the consequences of the impact in detail so that they can be extrapolated to future collisions&lt;/h2&gt;
  2156.  
  2157. &lt;p&gt;This is also the first time that a mission has returned to a small body of which we already have images, but which we already know have nothing to do with what it has become. On the basis of current data – which is very partial – predictions are subject to considerable uncertainties, and several results are possible.&lt;/p&gt;
  2158.  
  2159. &lt;p&gt;In fact, the DART data provides us with the initial conditions of the impact, but we lack the final result and the properties of the target that are involved in its response to the impact. Modelling based on the initial conditions provided by DART and the actual internal properties of the target that have yet to be measured, must reproduce the final result. The idea is to reduce the &lt;em&gt;free parameters&lt;/em&gt; as much as possible to ensure that the models succeed in reproducing the impact, not because unknown parameters have been adjusted to achieve the desired result, but because they are valid and reliably capture the phenomenon on a scale that is inaccessible in terrestrial laboratories.&lt;/p&gt;
  2160.  
  2161. &lt;p&gt;These validated models will later enable us to calibrate the impact energy required to deflect other asteroids with known properties.&lt;/p&gt;&lt;img src="https://counter.theconversation.com/content/240394/count.gif" alt="The Conversation" width="1" height="1" /&gt;
  2162. &lt;p class="fine-print"&gt;&lt;em&gt;&lt;span&gt;Patrick Michel ne travaille pas, ne conseille pas, ne possède pas de parts, ne reçoit pas de fonds d&amp;#39;une organisation qui pourrait tirer profit de cet article, et n&amp;#39;a déclaré aucune autre affiliation que son organisme de recherche.&lt;/span&gt;&lt;/em&gt;&lt;/p&gt;</content>
  2163.    <summary>In 2022, a probe was sent crashing into an asteroid as part of a “planetary defence” test. This Monday, the second part of the mission flies off to study the consequences of the impact.</summary>
  2164.    <author>
  2165.      <name>Patrick Michel, Astrophysicien, Directeur de Recherche au CNRS, Responsable Scientifique de la mission spatiale Hera (ESA), Observatoire de la Côte d’Azur, Laboratoire Lagrange, Université Côte d’Azur</name>
  2166.      <foaf:homepage rdf:resource="https://theconversation.com/profiles/patrick-michel-1378575"/>
  2167.    </author>
  2168.    <rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
  2169.  </entry>
  2170.  <entry>
  2171.    <id>tag:theconversation.com,2011:article/240279</id>
  2172.    <published>2024-10-02T11:22:23Z</published>
  2173.    <updated>2024-10-02T11:22:23Z</updated>
  2174.    <link rel="alternate" type="text/html" href="https://theconversation.com/a-ring-of-fire-eclipse-is-taking-place-in-south-america-and-the-pacific-heres-how-eclipses-happen-240279"/>
  2175.    <title>A ‘ring of fire’ eclipse is taking place in South America and the Pacific. Here’s how eclipses happen</title>
  2176.    <content type="html">&lt;p&gt;An &lt;a href="https://www.nesdis.noaa.gov/annular-solar-eclipse"&gt;annular eclipse&lt;/a&gt;, sometimes known as a “ring of fire” eclipse, is taking place &lt;a href="https://www.timeanddate.com/eclipse/solar/2024-october-2"&gt;on October 2&lt;/a&gt;. It will be visible from Argentina and Chile, while a partial eclipse will be seen in parts of the Pacific, other parts of South America and from Antarctica.&lt;/p&gt;
  2177.  
  2178. &lt;p&gt;Throughout history, eclipses have fascinated people. People around the world have
  2179. wondered about their significance and what causes them. Unsurprisingly, given their impressive nature, &lt;a href="https://theconversation.com/how-ancient-cultures-explained-eclipses-79887"&gt;various mystical causes and effects&lt;/a&gt; have been attributed to eclipses over the centuries. &lt;/p&gt;
  2180.  
  2181. &lt;p&gt;I’m going to provide more grounded answers to these questions. But as you’ll see, the answers often demand another question.&lt;/p&gt;
  2182.  
  2183. &lt;h2&gt;Why do eclipses happen?&lt;/h2&gt;
  2184.  
  2185. &lt;p&gt;The Earth goes around the Sun once per year in an orbit. The Moon goes around the Earth once per month in a smaller orbit. The Moon passes between us and the Sun, blocking out sunlight and casting a shadow on the Earth.&lt;/p&gt;
  2186.  
  2187.  
  2188.  
  2189. &lt;h2&gt;Why don’t eclipses happen every month?&lt;/h2&gt;
  2190.  
  2191. &lt;p&gt;The Moon’s path around the Earth is tilted with respect to the Earth’s path around the Sun. This means that, most of the time, the Moon passes either above or
  2192. below the Sun from our perspective, so it doesn’t block out any sunlight.&lt;/p&gt;
  2193.  
  2194.  
  2195.  
  2196. &lt;p&gt;As the diagram above shows, the Moon orbits at an angle. Notice how the Moon’s shadow now misses the Earth.&lt;/p&gt;
  2197.  
  2198. &lt;h2&gt;What’s the difference between a total and a partial eclipse?&lt;/h2&gt;
  2199.  
  2200. &lt;p&gt;Because the Sun is bigger than the Moon, there’s only a small cone of full shadow
  2201. called the &lt;a href="https://www.britannica.com/science/umbra-eclipse"&gt;“umbra”&lt;/a&gt; in which the sun is fully blocked. This causes a total eclipse.
  2202. Outside the umbra is a much larger area &lt;a href="https://www.britannica.com/science/penumbra-eclipse"&gt;called the “penumbra”&lt;/a&gt; where part of the
  2203. Sun is blocked, but part of it is visible. This causes a partial eclipse.&lt;/p&gt;
  2204.  
  2205. &lt;figure class="align-center "&gt;
  2206.            &lt;img alt="The difference between total and partial eclipses." src="https://images.theconversation.com/files/622829/original/file-20241001-16-emtcao.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;fit=clip" srcset="https://images.theconversation.com/files/622829/original/file-20241001-16-emtcao.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=237&amp;amp;fit=crop&amp;amp;dpr=1 600w, https://images.theconversation.com/files/622829/original/file-20241001-16-emtcao.jpg?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=237&amp;amp;fit=crop&amp;amp;dpr=2 1200w, https://images.theconversation.com/files/622829/original/file-20241001-16-emtcao.jpg?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=237&amp;amp;fit=crop&amp;amp;dpr=3 1800w, https://images.theconversation.com/files/622829/original/file-20241001-16-emtcao.jpg?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=297&amp;amp;fit=crop&amp;amp;dpr=1 754w, https://images.theconversation.com/files/622829/original/file-20241001-16-emtcao.jpg?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=297&amp;amp;fit=crop&amp;amp;dpr=2 1508w, https://images.theconversation.com/files/622829/original/file-20241001-16-emtcao.jpg?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=297&amp;amp;fit=crop&amp;amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"&gt;
  2207.            &lt;figcaption&gt;
  2208.              &lt;span class="caption"&gt;The difference between total and partial eclipses.&lt;/span&gt;
  2209.              &lt;span class="attribution"&gt;&lt;span class="source"&gt;Oisin Creaner. Inset images: NASA/Nat Gopalswamy (2024) (total eclipse) Hinode/XRT (2024) (partial eclipse)&lt;/span&gt;&lt;/span&gt;
  2210.            &lt;/figcaption&gt;
  2211.          &lt;/figure&gt;
  2212.  
  2213. &lt;h2&gt;What’s special about a total eclipse?&lt;/h2&gt;
  2214.  
  2215. &lt;p&gt;A total eclipse of the Sun from Earth is pretty special &lt;a href="https://theconversation.com/solar-eclipses-result-from-a-fantastic-celestial-coincidence-of-scale-and-distance-224113"&gt;because of a lucky
  2216. coincidence&lt;/a&gt;. The Sun is 400 times larger in diameter than the Moon, and the Sun is also about 400 times further away than the Moon. &lt;/p&gt;
  2217.  
  2218. &lt;p&gt;This means that they appear to be about the same size, so if you get them lined up just right, the Moon can fully block out the Sun, with very little spare, allowing you to &lt;a href="https://scied.ucar.edu/learning-zone/sun-space-weather/corona"&gt;see the “corona”&lt;/a&gt; (meaning crown) of the Sun. We can use the patterns in the corona to study the Sun’s magnetic field, but that’s a story for another day.&lt;/p&gt;
  2219.  
  2220. &lt;figure class="align-center "&gt;
  2221.            &lt;img alt="An image of a Total eclipse showing the Corona of the Sun." src="https://images.theconversation.com/files/622836/original/file-20241001-17-nti5v3.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;fit=clip" srcset="https://images.theconversation.com/files/622836/original/file-20241001-17-nti5v3.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=491&amp;amp;fit=crop&amp;amp;dpr=1 600w, https://images.theconversation.com/files/622836/original/file-20241001-17-nti5v3.png?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=491&amp;amp;fit=crop&amp;amp;dpr=2 1200w, https://images.theconversation.com/files/622836/original/file-20241001-17-nti5v3.png?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=600&amp;amp;h=491&amp;amp;fit=crop&amp;amp;dpr=3 1800w, https://images.theconversation.com/files/622836/original/file-20241001-17-nti5v3.png?ixlib=rb-4.1.0&amp;amp;q=45&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=617&amp;amp;fit=crop&amp;amp;dpr=1 754w, https://images.theconversation.com/files/622836/original/file-20241001-17-nti5v3.png?ixlib=rb-4.1.0&amp;amp;q=30&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=617&amp;amp;fit=crop&amp;amp;dpr=2 1508w, https://images.theconversation.com/files/622836/original/file-20241001-17-nti5v3.png?ixlib=rb-4.1.0&amp;amp;q=15&amp;amp;auto=format&amp;amp;w=754&amp;amp;h=617&amp;amp;fit=crop&amp;amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"&gt;
  2222.            &lt;figcaption&gt;
  2223.              &lt;span class="caption"&gt;An image of a total eclipse showing the corona of the Sun.&lt;/span&gt;
  2224.              &lt;span class="attribution"&gt;&lt;span class="source"&gt;NASA/Nat Gopalswamy&lt;/span&gt;&lt;/span&gt;
  2225.            &lt;/figcaption&gt;
  2226.          &lt;/figure&gt;
  2227.  
  2228. &lt;h2&gt;What’s an annular eclipse?&lt;/h2&gt;
  2229.  
  2230. &lt;p&gt;An annular (meaning ring) eclipse is when the umbra doesn’t quite reach the Earth. This means that you can see part of the Sun peeking out around the Moon on all sides. This causes the Sun to appear as a ring around the dark shadow caused by the Moon.&lt;/p&gt;
  2231.  
  2232.  
  2233.  
  2234. &lt;p&gt;This happens because the orbit of the Moon isn’t a circle, it’s an ellipse (like an oval or
  2235. squashed circle). This means that the distance from the Earth to the Moon varies, so it seems to get bigger and smaller. At its closest point (perigee), the Moon
  2236. appears to be 14% bigger than when it’s at its furthest point (apogee). &lt;/p&gt;
  2237.  
  2238. &lt;p&gt;The Earth’s orbit around the Sun is also elliptical, but the difference isn’t as large. Total eclipses happen when the Moon is close to Earth, and so can block out the whole Sun. Annular eclipses happen when the Moon is further away, and can’t completely cover it.&lt;/p&gt;
  2239.  
  2240.  
  2241.  
  2242. &lt;p&gt;The closer the Moon is to the Earth, the larger it appears to be. (The real effect is about 14% difference in size).&lt;/p&gt;
  2243.  
  2244. &lt;p&gt;Eclipses happen in lots of places. Just as the Moon casts a shadow on the Earth, the Earth can cast a shadow on the Moon. We call that a lunar eclipse, because the Moon seems to go dark. Because the Earth is much bigger than the Moon, the entire Moon can be in the Earth’s umbra. &lt;/p&gt;
  2245.  
  2246. &lt;p&gt;However, Earth’s atmosphere refracts (bends) some sunlight around the Earth so a little light, mostly red light, makes it through, causing the “blood moon” effect.&lt;/p&gt;
  2247.  
  2248. &lt;p&gt;From the Moon, you’d see a total eclipse of the Sun. The Earth, would appear to be four times the size of the Sun (it’s actually about 100 times smaller in diameter), and would block out the Sun, except for a reddish halo of light. This halo would come from all the sunsets and sunrises happening around the world at once.&lt;/p&gt;&lt;img src="https://counter.theconversation.com/content/240279/count.gif" alt="The Conversation" width="1" height="1" /&gt;
  2249. &lt;p class="fine-print"&gt;&lt;em&gt;&lt;span&gt;Oisin Creaner receives funding from by the National Open Research Forum (NORF) Open Research Fund 2023, Strand II: Open Research Stimulus Call 2023. This funding is provided through the Higher Education Authority (HEA) and from Science Foundation Ireland through ML-Labs the SFI Centre for Research Training in Machine Learning (Grant No. 18/CRT/6183). He is the Secretary of the Astronomical Association of Ireland, a member of the Royal Irish Academy&amp;#39;s multidisciplinary committee for Physical, Chemical and Mathematical Sciences and Treasurer of the Institute of Physics&amp;#39; Computational Physics Group.&lt;/span&gt;&lt;/em&gt;&lt;/p&gt;</content>
  2250.    <summary>Argentina and Chile will see the ‘ring’, but other regions will see a partial eclipse.</summary>
  2251.    <author>
  2252.      <name>Oisin Creaner, Assistant Professor of Physical Sciences, Dublin City University</name>
  2253.      <foaf:homepage rdf:resource="https://theconversation.com/profiles/oisin-creaner-1525673"/>
  2254.    </author>
  2255.    <rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
  2256.  </entry>
  2257. </feed>
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