Our 5 Dwarf Planets | Britannica

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They write new content and verify and edit content received from contributors.</div> </a> <div data-popper-arrow></div> </div> <span class="btn btn-link editor-link p-0 qa-byline-link font-12 "> The Editors of Encyclopaedia Britannica</span></div></div> </div> <article class="topic-content content"><div class="topic-paragraph font-serif md-list-intro pt-15 pb-20"><figure class="md-assembly md-feature-assembly print-false" data-type="1" data-descid="1"><div class="md-assembly-wrapper card-media" data-type="image"><a href="https://cdn.britannica.com/16/172316-131-51333C97/Pluto-Crop-asset-IC-code-view-surface.jpg" target="_blank" class="gtm-assembly-link position-relative d-flex align-items-center justify-content-center " data-href="*0"><img src="https://cdn.britannica.com/16/172316-131-51333C97/Pluto-Crop-asset-IC-code-view-surface.jpg?w=1000" alt="Pluto. Crop of asset: 172304/IC code: pluto0010 at 270 degrees. The Changing Faces of Pluto. Most detailed view to date of the entire surface of the dwarf planet Pluto, constructed from multiple NASA Hubble Space Telescope photographs 2002-03." data-width="900" data-height="675" loading="eager"><button class="magnifying-glass btn btn-circle position-absolute shadow btn-white top-10 right-10" aria-label="Zoom in"><em class="material-icons link-blue" data-icon="zoom_in"></em></button></a></div><figcaption class=""><div class="md-assembly-caption text-muted font-14 font-serif "><span></span></div><cite class="credit d-block mt-5">M. Buie (Southwest Research Institute)/ESA/NASA</cite></figcaption></figure><p class="topic-paragraph">There was much outrage and confusion in 2006 when Pluto lost its status as our solar system’s ninth planet. But we didn’t just lose a planet—we gained five dwarf planets! The term <em>dwarf planet</em> is defined by the International Astronomical Union (IAU) as "a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite." There are hundreds of objects in our solar system that have the potential to be classified as <a href="https://www.britannica.com/science/dwarf-planet" class="md-crosslink " data-show-preview="true">dwarf planets</a>, but so far only five are official. Read on to meet our (current) five.</p><span class="MOD"></span></div><ul class="md-list-order-reverse md-mendel-list" style="counter-reset: item 6"><li><h2>Pluto</h2><div><figure class="md-assembly md-feature-assembly print-false" data-type="1" data-descid="1"><div class="md-assembly-wrapper card-media" data-type="image"><a href="https://cdn.britannica.com/78/91878-050-6215C37B/Artist-Pluto-rendering-spacecraft-moons-New-Horizons.jpg" target="_blank" class="gtm-assembly-link position-relative d-flex align-items-center justify-content-center " data-href="*121430"><img src="https://cdn.britannica.com/78/91878-050-6215C37B/Artist-Pluto-rendering-spacecraft-moons-New-Horizons.jpg?w=1000" alt="Artist's concept of the New Horizons spacecraft as it approaches Pluto and its three moons in summer of 2015." data-width="1600" data-height="1255" loading="eager"><button class="magnifying-glass btn btn-circle position-absolute shadow btn-white top-10 right-10" aria-label="Zoom in"><em class="material-icons link-blue" data-icon="zoom_in"></em></button></a></div><figcaption class=""><div class="md-assembly-caption text-muted font-14 font-serif "><span><a class="gtm-assembly-link md-assembly-title font-weight-bold d-inline font-sans-serif mr-5 media-overlay-link" target="_blank" href="https://cdn.britannica.com/78/91878-050-6215C37B/Artist-Pluto-rendering-spacecraft-moons-New-Horizons.jpg" data-href="*121430">New Horizons near Pluto</a><span>Artist's rendering of the New Horizons spacecraft approaching Pluto and its three moons.</span></span></div><cite class="credit d-block mt-5">NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute</cite></figcaption></figure><p class="topic-paragraph">First is <a href="https://www.britannica.com/place/Pluto-dwarf-planet" class="md-crosslink " data-show-preview="true">Pluto</a>, the former planet. Discovered in 1930, it was named for the Roman god of the underworld. Its largest moon, Charon, is almost its equal in size and the two are often considered a double system. Telescopes on Earth have not been able to get a clear view of this faraway world, but the spacecraft New Horizons, which made a flyby in 2015, gathered much previously unknown information about Pluto. At about 5.9 billion km (3.7 billion miles or 39.5 astronomical units) from the Sun, it is so remote that the Sun’s light takes 5 hours to reach it. It is so cold there that gases such as carbon monoxide exist in ice form.</p><span class="MOD"></span></div><span class="LIST-ITEM-1"></span></li><li><h2>Eris</h2><div><figure class="md-assembly md-feature-assembly print-false" data-type="1" data-descid="1"><div class="md-assembly-wrapper card-media" data-type="image"><a href="https://cdn.britannica.com/05/97005-050-2C15528B/image-Hubble-Space-Telescope-light-Eris-planet.jpg" target="_blank" class="gtm-assembly-link position-relative d-flex align-items-center justify-content-center " data-href="*122529"><img src="https://cdn.britannica.com/05/97005-050-2C15528B/image-Hubble-Space-Telescope-light-Eris-planet.jpg?w=1000" alt="NASA's Hubble Space telescope resovled Kuiper Belt object "Xena" for the first time and found that it is only just a little larger than Pluto. Eris, 10th planet, UB 313, UB313, Eris" data-width="783" data-height="823" loading="eager"><button class="magnifying-glass btn btn-circle position-absolute shadow btn-white top-10 right-10" aria-label="Zoom in"><em class="material-icons link-blue" data-icon="zoom_in"></em></button></a></div><figcaption class=""><div class="md-assembly-caption text-muted font-14 font-serif "><span><a class="gtm-assembly-link md-assembly-title font-weight-bold d-inline font-sans-serif mr-5 media-overlay-link" target="_blank" href="https://cdn.britannica.com/05/97005-050-2C15528B/image-Hubble-Space-Telescope-light-Eris-planet.jpg" data-href="*122529">An image taken by the Hubble Space Telescope showing the dwarf planet Eris in visible light.</a></span></div><cite class="credit d-block mt-5">ESA/NASA</cite></figcaption></figure><p class="topic-paragraph">Eris was the troublemaker that led to Pluto’s reclassification. It was discovered in 2005 and, because it is close in size to Pluto, briefly considered the solar system’s tenth planet. After its discovery, astronomers were forced to reconsider the definition of "planet" entirely. <a href="https://www.britannica.com/place/Eris-astronomy" class="md-crosslink " data-show-preview="true">Eris</a> was named after the Greek goddess Eris, who started the Trojan war by causing a fight among some of the other goddesses. Its discoverers briefly nicknamed it "Xena" after the TV warrior princess. Its one known moon is named Dysnomia, after Eris’s daughter, the goddess of lawlessness.</p><span class="MOD"></span></div><span class="LIST-ITEM-2"></span></li><li><h2>Ceres</h2><div><figure class="md-assembly md-feature-assembly print-false" data-type="1" data-descid="1"><div class="md-assembly-wrapper card-media" data-type="image"><a href="https://cdn.britannica.com/03/97003-050-D1606728/Series-images-Ceres-rotation-Hubble-Space-Telescope.jpg" target="_blank" class="gtm-assembly-link position-relative d-flex align-items-center justify-content-center " data-href="*107535"><img src="https://cdn.britannica.com/03/97003-050-D1606728/Series-images-Ceres-rotation-Hubble-Space-Telescope.jpg?w=1000" alt="Series of six images showing rotation of Asteroid Ceres, taken by NASA's Hubble Space Telescope." data-width="1321" data-height="1600" loading="eager"><button class="magnifying-glass btn btn-circle position-absolute shadow btn-white top-10 right-10" aria-label="Zoom in"><em class="material-icons link-blue" data-icon="zoom_in"></em></button></a></div><figcaption class=""><div class="md-assembly-caption text-muted font-14 font-serif "><span><a class="gtm-assembly-link md-assembly-title font-weight-bold d-inline font-sans-serif mr-5 media-overlay-link" target="_blank" href="https://cdn.britannica.com/03/97003-050-D1606728/Series-images-Ceres-rotation-Hubble-Space-Telescope.jpg" data-href="*107535">rotation of Ceres</a><span>Series of six images showing the rotation of Ceres, taken by the Hubble Space Telescope. </span></span></div><cite class="credit d-block mt-5">ESA/STScI/NASA</cite></figcaption></figure><p class="topic-paragraph">Unlike the other dwarf planets, <a href="https://www.britannica.com/place/Ceres-dwarf-planet" class="md-crosslink " data-show-preview="true">Ceres</a> is also an asteroid. The largest known asteroid in the asteroid belt, in fact, and the first to have been discovered. It was found in 1801. The name Ceres comes from the Roman grain goddess who was the patron goddess of Sicily, and with it began the tradition of naming main-belt asteroids after female characters from Greco-Roman mythology. At about 2.77 astronomical units (AU; about 414 million km [257 million miles]) from the Sun, it is by far the nearest of the dwarf planets.</p><span class="MOD"></span></div><span class="LIST-ITEM-3"></span></li><li><h2>Haumea</h2><div><figure class="md-assembly md-feature-assembly print-false" data-type="1" data-descid="1"><div class="md-assembly-wrapper card-media" data-type="image"><a href="https://cdn.britannica.com/66/137066-004-13F11781/rendering-Artist-moons-Haumea.jpg" target="_blank" class="gtm-assembly-link position-relative d-flex align-items-center justify-content-center " data-href="*139800"><img src="https://cdn.britannica.com/66/137066-004-13F11781/rendering-Artist-moons-Haumea.jpg?w=1000" alt="Artist's rendering of Haumea and its moons." data-width="536" data-height="450" loading="eager"><button class="magnifying-glass btn btn-circle position-absolute shadow btn-white top-10 right-10" aria-label="Zoom in"><em class="material-icons link-blue" data-icon="zoom_in"></em></button></a></div><figcaption class=""><div class="md-assembly-caption text-muted font-14 font-serif "><span><a class="gtm-assembly-link md-assembly-title font-weight-bold d-inline font-sans-serif mr-5 media-overlay-link" target="_blank" href="https://cdn.britannica.com/66/137066-004-13F11781/rendering-Artist-moons-Haumea.jpg" data-href="*139800">Haumea</a><span>Artist's rendering of Haumea and its moons.</span></span></div><cite class="credit d-block mt-5">NASA, ESA, and A. Feild (STScI)</cite></figcaption></figure><p class="topic-paragraph">Haumea was discovered in 2003 and became our fifth dwarf planet in 2008. Its shape and composition set it apart from other objects in the Kuiper belt, and it is one of the fastest rotating large objects in the solar system. <a href="https://www.britannica.com/place/Haumea" class="md-crosslink " data-show-preview="true">Haumea</a> is elongated in shape and is made up of a rocky interior covered by a thin icy crust. It was named for the Hawaiian goddess of birth and fertility. Its two moons, Hi‘iaka and Namaka, were named after goddess Haumea’s daughters.</p><span class="MOD"></span></div><span class="LIST-ITEM-4"></span></li><li><h2>Makemake</h2><div><figure class="md-assembly md-feature-assembly print-false" data-type="1" data-descid="1"><div class="md-assembly-wrapper card-media" data-type="image"><a href="https://cdn.britannica.com/92/136792-004-CF8C573F/Makemake-Hubble-Space-Telescope.jpg" target="_blank" class="gtm-assembly-link position-relative d-flex align-items-center justify-content-center " data-href="*139173"><img src="https://cdn.britannica.com/92/136792-004-CF8C573F/Makemake-Hubble-Space-Telescope.jpg?w=1000" alt="Makemake, photographed by the Hubble Space Telescope." data-width="402" data-height="402" loading="eager"><button class="magnifying-glass btn btn-circle position-absolute shadow btn-white top-10 right-10" aria-label="Zoom in"><em class="material-icons link-blue" data-icon="zoom_in"></em></button></a></div><figcaption class=""><div class="md-assembly-caption text-muted font-14 font-serif "><span><a class="gtm-assembly-link md-assembly-title font-weight-bold d-inline font-sans-serif mr-5 media-overlay-link" target="_blank" href="https://cdn.britannica.com/92/136792-004-CF8C573F/Makemake-Hubble-Space-Telescope.jpg" data-href="*139173">Makemake</a><span>Makemake, photographed by the Hubble Space Telescope.</span></span></div><cite class="credit d-block mt-5">National Aeronautics and Space Administration</cite></figcaption></figure><p class="topic-paragraph">Makemake was the last of the dwarf planets to be discovered. Scientists found it shortly after Easter in 2005 and nicknamed it “Easterbunny.” Its official name comes from the Rapa Nui fertility god. The Rapa Nui are the native people of Easter Island (you may know it from its giant stone statues), which brings the story full circle. <a href="https://www.britannica.com/place/Makemake" class="md-crosslink " data-show-preview="true">Makemake</a> has no known moons. Its surface is thought to be composed of frozen methane, ethane, and nitrogen. Although it is in many ways similar to Pluto, it appears to have no significant atmosphere.</p><span class="MOD"></span></div><span class="LIST-ITEM-5"></span></li></ul><span class="AM-END-OF-ARTICLE am-inline"></span></article> </div> </div> </div> <aside class="cm-rightrail d-none d-md-block ad-rail"></aside> </div> </div> </div> <div class="grid gx-0"> <div class="col"> <div class="md-loading hidden display-4 font-weight-normal"></div> <div class="text-center my-20 mb-100"> <button class="md-infinite-load-next btn btn-blue" data-value="next-page">Load More</button> </div> </div> <div class="col-md-da-320 hidden-xs"> </div> </div> </div> </div> </main> <div id="md-footer"></div> <noscript><iframe src="//www.googletagmanager.com/ns.html?id=GTM-5W6NC8" height="0" width="0" style="display:none;visibility:hidden"></iframe></noscript> <script type="text/javascript" id="_informizely_script_tag"> var IzWidget = IzWidget || {}; (function (d) { var scriptElement = d.createElement('script'); scriptElement.type = 'text/javascript'; scriptElement.async = true; scriptElement.src = "https://insitez.blob.core.windows.net/site/f780f33e-a610-4ac2-af81-3eb184037547.js"; var node = d.getElementById('_informizely_script_tag'); node.parentNode.insertBefore(scriptElement, node); } )(document); </script>  <script> window.ap3c = window.ap3c || {}; var ap3c = window.ap3c; ap3c.cmd = ap3c.cmd || []; ap3c.cmd.push(function() { ap3c.init('ZO4siT4cLwnykPnzZWJtd3Byb2Q', 'https://engage.email.britannica.com/'); ap3c.track({v: 0}); }); ap3c.activity = function(act) { ap3c.act = (ap3c.act || []); ap3c.act.push(act); }; var s, t; s = document.createElement('script'); s.type = 'text/javascript'; s.src = "https://engage.email.britannica.com/app.js"; t = document.getElementsByTagName('script')[0]; t.parentNode.insertBefore(s, t); </script> <script class="marketing-page-info" type="application/json"> {"pageType":"List","templateName":null,"pageNumber":1,"pagesTotal":11,"pageId":3776,"pageLength":null,"initialLoad":true,"lastPageOfScroll":false} </script> <script class="marketing-content-info" type="application/json"> [] </script> <script src="https://cdn.britannica.com/mendel-resources/3-133/js/libs/jquery-3.5.0.min.js?v=3.133.36"></script> <script type="text/javascript" data-type="Init Mendel Code Splitting"> (function() { $.ajax({ dataType: 'script', cache: true, url: 'https://cdn.britannica.com/mendel-resources/3-133/dist/list-page.js?v=3.133.36' }); })(); </script> <script class="analytics-metadata" type="application/json"> {"leg":"D","adLeg":"C","userType":"ANONYMOUS","pageType":"List","pageSubtype":null,"articleTemplateType":null,"gisted":false,"pageNumber":1,"hasSummarizeButton":false,"hasAskButton":false} </script> <script type="text/javascript"> EBStat={accountId:-1,hostnameOverride:'webstats.eb.com',domain:'www.britannica.com', json:''}; </script> <script type="text/javascript"> ( function() { $.ajax( { dataType: 'script', cache: true, url: '//www.britannica.com/webstats/mendelstats.js?v=1' } ) .done( function() { try {writeStat(null,EBStat);} catch(err){} } ); })(); </script> <div id="bc-fixed-dialogue"></div> </body> </html>

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Our 5 Dwarf Planets | Britannica