{"id":650018,"date":"2026-08-22T02:07:13","date_gmt":"2026-08-22T02:07:13","guid":{"rendered":"https:\/\/www.europesays.com\/ie\/650018\/"},"modified":"2026-08-22T02:07:13","modified_gmt":"2026-08-22T02:07:13","slug":"astronomers-discover-rare-mega-earth-exoplanet-gliese-523b","status":"publish","type":"post","link":"https:\/\/www.europesays.com\/ie\/650018\/","title":{"rendered":"Astronomers Discover Rare \u2018Mega-Earth\u2019 Exoplanet: Gliese 523b"},"content":{"rendered":"

Gliese 523b (GJ 523b) is a young, ultra-dense planet that orbits almost perpendicular to its star\u2019s spin, according to a team of U.S. astronomers.<\/strong><\/p>\n

\"An<\/p>\n

An artist\u2019s impression of a giant exoplanet. Image credit: Sci.News.<\/p>\n

\u201cPeople have been using the phrase \u2018mega-Earth<\/a>\u2019 for more than a decade, but we\u2019ve never had a planet that let us say concretely what one is,\u201d said Dr. Thomas Beatty, an astronomer at the University of Wisconsin-Madison<\/a>.<\/p>\n

\u201cGliese 523b finally does. What is also striking is that nailing down the definition of a mega-Earth isn\u2019t something us astronomers can really do by ourselves.\u201d<\/p>\n

\u201cWe need geologists who understand how iron and rock behave at pressures no laboratory on Earth can reach, and atmospheric scientists who can tell us how much of what we measured is rock at all.\u201d<\/p>\n

The newfound planet orbits Gliese 523<\/a> (GJ 523), a mid-K dwarf star roughly 87 light-years away from Earth, completing one lap every 17.75 days.<\/p>\n

The alien world is about 2.55 times Earth\u2019s radius but 23.5 times Earth\u2019s mass, giving it a bulk density of 7.8 grams per cm3 \u2014 denser than our home planet itself, despite being large enough to typically host a thick atmosphere.<\/p>\n

\u201cThis isn\u2019t what we expected at all,\u201d said Max Kroft, a graduate student at the University of Wisconsin-Madison.<\/p>\n

\u201cDense planets like this aren\u2019t uncommon, but they\u2019re usually small rocky planets similar to Earth or Mercury. This planet is two and a half times bigger than the Earth.\u201d<\/p>\n

Using radial velocity data from the NEID spectrograph on the WIYN Telescope at Kitt Peak National Observatory, combined with earlier transit detections from NASA\u2019s TESS mission, the astronomers confirmed the planetary nature of Gliese 523b.<\/p>\n

\u201cWe picked out this planet based on what we thought its size and temperature were,\u201d Kroft said.<\/p>\n

\u201cA bigger planet makes a bigger dip, so we get an idea of the size, and based on how often that dip happens, we get the distance of its orbit, and we can use that to estimate the temperature of the exoplanet.\u201d<\/p>\n

By analyzing the rotation rates of Gliese 523 and several companion stars moving through space together, the researchers estimated the system is only about 169 million years old.<\/p>\n

They also determined that the planet\u2019s orbit is inclined at least 71 degrees relative to its star\u2019s equator, meaning Gliese 523b likely travels over the star\u2019s poles rather than around its equator, similar to how a satellite might orbit Earth pole-to-pole rather than tracing the equator.<\/p>\n

The combination of high mass, apparent lack of an atmosphere, youth, and steep orbital tilt is difficult to reconcile with standard theories of how planets form and evolve.<\/p>\n

The scientists explored several possible explanations, including violent gravitational interactions with an undetected outer companion, misalignment inherited from a warped protoplanetary disk, or a formation process involving giant impacts or delayed gas accretion that could have prevented the planet from ever accumulating a thick atmosphere.<\/p>\n

\u201cWe put forward several possible theories in the paper, including the possibility that the planet had some of its atmosphere ripped off when it orbited too close to its star or that it actually began as two planets that collided and lost atmosphere in the heat of the crash,\u201d Kroft said.<\/p>\n

\u201cIt kind of blows away. A planet can\u2019t hold on to its atmosphere if it\u2019s really hot, and so you could be left with this big glob of rock made by these two planets with very little atmosphere.\u201d<\/p>\n

The team\u2019s paper<\/a> will be published in the Astronomical Journal<\/a>.<\/p>\n

_____<\/p>\n

Maxwell A. Kroft et al. 2026. GJ 523b is a Massive, 170 Myr-old Mega-Earth, Likely on a Polar Orbit. AJ, in press; arXiv: 2603.24682<\/p>\n","protected":false},"excerpt":{"rendered":"Gliese 523b (GJ 523b) is a young, ultra-dense planet that orbits almost perpendicular to its star\u2019s spin, according…\n","protected":false},"author":2,"featured_media":650019,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":"","_share_on_mastodon":"0"},"categories":[77],"tags":[10210,18,18060,184841,274733,274734,274735,19,17,83584,184843,1024,17210,133,98307,274736,241067],"class_list":["post-650018","post","type-post","status-publish","format-standard","has-post-thumbnail","category-science","tag-atmosphere","tag-eire","tag-exoplanet","tag-gj-523","tag-gj-523b","tag-gliese-523","tag-gliese-523b","tag-ie","tag-ireland","tag-kitt-peak-national-observatory","tag-mega-earth","tag-nasa","tag-orbit","tag-science","tag-tess","tag-wiyn","tag-wiyn-telescope"],"share_on_mastodon":{"url":"https:\/\/pubeurope.com\/@ie\/117136723819712473","error":""},"_links":{"self":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/posts\/650018","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/comments?post=650018"}],"version-history":[{"count":0,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/posts\/650018\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/media\/650019"}],"wp:attachment":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/media?parent=650018"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/categories?post=650018"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/tags?post=650018"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}