{"id":241836,"date":"2025-10-26T10:54:09","date_gmt":"2025-10-26T10:54:09","guid":{"rendered":"https:\/\/www.newsbeep.com\/au\/241836\/"},"modified":"2025-10-26T10:54:09","modified_gmt":"2025-10-26T10:54:09","slug":"new-possible-volcanic-exomoon-orbiting-searing-hot-exoplanet","status":"publish","type":"post","link":"https:\/\/www.newsbeep.com\/au\/241836\/","title":{"rendered":"New possible volcanic exomoon orbiting searing hot exoplanet"},"content":{"rendered":"

\"MottledView larger<\/a>. | In this image from NASA\u2019s Galileo<\/a> spacecraft \u2013 captured in 1997 \u2013 an active volcano erupts on the limb, or edge, of Jupiter\u2019s moon Io<\/a>. If it\u2019s real, the nearly discovered volcanic exomoon \u2013 some 700 light-years away \u2013 might be similar to Io. Image via NASA\/ JPL<\/a>\/ University of Arizona.<\/p>\n

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WASP-39b is a huge \u2018hot Jupiter\u2019 exoplanet about 700 light-years from Earth.
\nA volcanic exomoon might be orbiting this planet. The result comes from new observations from the Webb Space Telescope, which found sulfur dioxide on or near the planet.
\nThe discovery is similar to that of WASP-49b, which might also have a volcanic moon.<\/p>\n

Another possible volcanic exomoon?<\/p>\n

There are hundreds of moons in our solar system, our neighborhood of space. So it\u2019s logical there should be moons in other planetary systems as well. If so, we\u2019d call them exomoons. Astronomers have found a few candidate exomoons, but as yet none are confirmed. On October 14, 2025, a team of astronomers led by Apurva Oza<\/a> at the California Institute of Technology (Caltech) said<\/a> it\u2019s discovered a new strong candidate. The possible moon orbits the hot gas giant exoplanet<\/a> called WASP-39b<\/a>. <\/p>\n

The idea is that sulfur dioxide in the planet\u2019s atmosphere might come from a highly volcanic moon, reminiscent of Jupiter\u2019s moon Io<\/a>. These researchers used the James Webb Space Telescope<\/a> to find the sulfur dioxide.<\/p>\n

WASP-39b is a gas giant exoplanet \u2013 a hot Jupiter<\/a> \u2013 orbiting a G-type star<\/a> similar to our sun, about 700 light-years<\/a> away from Earth. It orbits very close to its star, completing an orbit in only four days. This means it is extremely hot, with a dayside temperature of 1,430 degrees Fahrenheit (776 degrees Celsius). Astronomers discovered the planet in 2011.<\/p>\n

The findings are similar to that of another possible exomoon accompanying WASP-49b<\/a>. Researchers said last year that this planet, also a hot Jupiter, might also have a volcanic exomoon.<\/p>\n

Nola Taylor Tillman wrote<\/a> about the intriguing possibility in Scientific American on October 14, 2025.<\/p>\n

The researchers published<\/a> their findings in a preprint paper on arXiv on September 10, 2025. The paper has been accepted for publication in the Monthly Notices of the Royal Astronomical Society.<\/p>\n

Detection of sulfur dioxide<\/p>\n

Astronomers said in 2023 that they detected sulfur dioxide in the atmosphere of WASP-39b. The James Webb Space Telescope was also used to make that detection. But is it really in the atmosphere, and where did it come from?<\/p>\n

The new study suggests that \u2013 similar to WASP-49b \u2013 the sulfur dioxide might originate from an orbiting exomoon.<\/p>\n

\"VolcanicView larger<\/a>. | Artist\u2019s concept of what WASP-39b<\/a> might look like. NASA\u2019s James Webb Space Telescope<\/a> found sulfur dioxide in its atmosphere in 2023, and now a new study says that it might originate from a volcanic exomoon orbiting the gas giant exoplanet<\/a>. Image via NASA<\/a>\/ ESA\/ CSA\/ Joseph Olmsted (STScI).
\nAn Io-like volcanic exomoon?<\/p>\n

The hypothesis is that a highly volcanic exomoon is orbiting WASP-39b. It would be similar to Jupiter\u2019s moon Io, which is the most volcanically active body in our solar system. Jupiter\u2019s immense gravity tugs at Io, which heats its interior. Oza said<\/a> in Scientific American that the process within the exomoon would be:<\/p>\n

\u2026 nearly identical with that of Io [and Jupiter] except that [WASP-39b] is very close to the star. The star is really cooking it, gravitationally and thermally as well.<\/p>\n

Data from the James Webb Space Telescope and other observatories suggests a supervolcanic exomoon may lurk around the giant exoplanet WASP-39b<\/p>\n

\u2014 Scientific American (@sciam.bsky.social)<\/a> 2025-10-14T18:41:56.986Z<\/a><\/p>\n

Unusual variations in the atmosphere<\/p>\n

In addition, astronomers have also found sodium and potassium in WASP-39b\u2019s atmosphere. They tracked the compounds, along with the sulfur dioxide, for over a decade. Notably, they found that they varied over time. The behavior suggested there might actually be an external source for them instead of the planet itself. Kurt Retherford<\/a>, a planetary scientist at the Southwest Research Institute in San Antonio, Texas, also told Scientific American:<\/p>\n

The fact that these particular species are varying really points to something that\u2019s more of a solid body, like a moon would be.<\/p>\n

Retherford has been skeptical of the moon hypothesis. But now, after seeing Oza\u2019s presentation last month at the joint Europlanet Science Congress\/Division of Planetary Sciences (EPSC-DPS<\/a>) conference in Helsinki, Finland, he thinks the exomoon explanation is more likely, saying:<\/p>\n

Before I saw his talk, I would have leaned more toward the planet itself.<\/p>\n

He now says that:<\/p>\n

An external, nonplanetary source for strange readings from WASP-39b is more sensible, maybe with an exomoon being the best explanation for the data as it stands right now.<\/p>\n

\"SmilingScientist Apurva Oza<\/a> at the California Institute of Technology (Caltech) is the lead researcher in the new study about a possible volcanic exomoon. Image via Caltech<\/a>.
\nCan hot Jupiters have moons?<\/p>\n

Astronomers think hot Jupiters first form much farther away from their stars and then gradually migrate inward. Any moons likely formed along with them. But scientists aren\u2019t sure if the moons could survive the trip closer to their stars. As astronomer David Kipping<\/a> at Columbia University in New York noted:<\/p>\n

We can think of lots of plausible ways for a moon to be lost. Holding onto it is hard.<\/p>\n

But Ren\u00e9 Heller<\/a> at the Max Planck Institute for Solar System Research in G\u00f6ttingen, Germany, thinks it\u2019s possible. In our solar system, Jupiter and Saturn might have also moved inward from where they first formed, although not as much as hot Jupiters. Heller said:<\/p>\n

Our solar system acts as an example for moving things inward and carrying their moons along with them.<\/p>\n

According to the study, the moon would need to be orbiting within one planetary radius of WASP-39b in order to survive the trip closer to the star. Heller is skeptical, and said:<\/p>\n

I think it\u2019s very implausible. Stability is a tough criterion.<\/p>\n

\"BigView larger<\/a>. | Artist\u2019s concept of WASP-49 b<\/a>, another gas giant exoplanet with a possible volcanic exomoon. Image via NASA<\/a>\/ JPL-Caltech.
\nMore study needed<\/p>\n

There are still many questions to be answered, and more study needed, to determine whether WASP-39b really does have a volcanic moon or not. As Kipping noted:<\/p>\n

I think it\u2019s questionable whether we understand stars enough to confidently assert that any variability we see, spectroscopically especially, cannot be the result of some process happening on the surface of the star itself. When your hypothesis can explain everything, it becomes very difficult to disprove it.<\/p>\n

On the other hand, Retherford says:<\/p>\n

It\u2019s more of a challenge for me to imagine the sodium, potassium and sulfur dioxide in the upper parts of the gas giant atmosphere.<\/p>\n

Heller added:<\/p>\n

I guess we would need a complementary method, an independent method to prove any predictions you have.<\/p>\n

Astronomers have already observed WASP-39b many times over the years. They did this when the planet transited in front of its star as seen from Earth. So as the researchers noted, it\u2019s possible that additional evidence for the moon could still be hiding in the transit data. Oza said:<\/p>\n

This technique is extremely sensitive to the mass of the moon, which could be smaller than our own moon or Io.<\/p>\n

Kipping added:<\/p>\n

It\u2019s a really intriguing signal that demands an explanation, and an exomoon can explain it. I think we should pursue it.<\/p>\n

Bottom line: Astronomers using the James Webb Space Telescope said they\u2019ve found evidence of a possible volcanic exomoon orbiting the hot Jupiter exoplanet WASP-39b.<\/p>\n

Source (preprint): Volcanic Satellites Tidally Venting Na, K, SO2 in Optical & Infrared Light<\/a><\/p>\n

Via Scientific American<\/a><\/p>\n

Paul Scott Anderson
\n View Articles<\/a><\/p>\n

About the Author:<\/p>\n

Paul Scott Anderson has had a passion for space exploration that began when he was a child when he watched Carl Sagan\u2019s Cosmos. He studied English, writing, art and computer\/publication design in high school and college. He later started his blog The Meridiani Journal in 2005, which was later renamed Planetaria. He also later started the blog Fermi Paradoxica, about the search for life elsewhere in the universe.
\n
\nWhile interested in all aspects of space exploration, his primary passion is planetary science and SETI. In 2011, he started writing about space on a freelance basis with Universe Today. He has also written for SpaceFlight Insider and AmericaSpace and has also been published in The Mars Quarterly. He also did some supplementary writing for the iOS app Exoplanet.
\n
\nHe has been writing for EarthSky since 2018, and also assists with proofing and social media.<\/p>\n","protected":false},"excerpt":{"rendered":"View larger. | In this image from NASA\u2019s Galileo spacecraft \u2013 captured in 1997 \u2013 an active volcano…\n","protected":false},"author":2,"featured_media":241837,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[64,63,3398,128,285,144333,144334],"class_list":{"0":"post-241836","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-science","8":"tag-au","9":"tag-australia","10":"tag-james-webb-space-telescope","11":"tag-science","12":"tag-space","13":"tag-volcanic-exomoon","14":"tag-wasp-139b"},"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/posts\/241836","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/comments?post=241836"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/posts\/241836\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/media\/241837"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/media?parent=241836"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/categories?post=241836"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/tags?post=241836"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}