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- NASA\u2019s Webb space telescope was used to find signs of water-ice clouds<\/strong> on the giant exoplanet known as Epsilon Indi Ab<\/em>. It\u2019s about 12 light-years away. <\/li>\n
- The discovery was a surprise.<\/strong> Jupiter has ammonia gas in the upper atmosphere. But astronomers found less ammonia for Epsilon Indi Ab than anticipated. They surmise there must be water-ice clouds there instead.<\/li>\n
- The presence of water-ice clouds on Epsilon Indi Ab would \u201cbreak\u201d existing computer models<\/strong> of Jupiter-like exoplanets. Is it back to the drawing board for models of these worlds?<\/li>\n<\/ul>\n
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A Jupiter-like exoplanet with water-ice clouds<\/h3>\n
Astronomers have found many hot Jupiters. These are gas giant exoplanets, similar to giant Jupiter in our own solar system, but orbiting their stars closely<\/em>. So they are much hotter than Jupiter. But now, researchers at the Max Planck Institute for Astronomy (MPIA) in Heidelberg, Germany, have made an interesting discovery. They used the James Webb Space Telescope (JWST) to examine a cooler Jupiter-like exoplanet, orbiting far<\/em> from its star. The researchers said on April 22, 2026, that the planet, Epsilon Indi Ab, appears to have water-ice clouds in its atmosphere. <\/p>\n
If they are indeed present, the clouds high in the atmosphere of this exo-Jupiter<\/em> will be similar to high-altitude cirrus clouds on Earth. <\/p>\n
Epsilon Indi Ab is about 12 light-years away. It orbits its star at about Neptune\u2019s distance from our sun, or about 30 AU. It takes 180 Earth-years to make a single orbit (in contrast to 12 years for Jupiter orbiting our sun, or 165 years for Neptune). It\u2019s massive, some 7.6 times the mass of Jupiter. But its diameter is about the same as that of Jupiter.<\/p>\n
The researchers published their new peer-reviewed results in The Astrophysical Journal Letters<\/em> on April 22, 2026.<\/p>\n
![\"Bright](\"https:\/\/earthsky.org\/upl\/2026\/04\/Epsilon-Indi-Ab-coronograph-iamge-JWST.jpg\")
Coronograph image from the James Webb Space Telescope showing Epsilon Indi Ab (bright dot in upper left). A coronagraph obscures the star\u2019s light, so that the planet can be seen. Image via Matthews et al.\/ The Astrophysical Journal Letters (CC BY 4.0).<\/figcaption><\/figure>\n Here\u2019s why it\u2019s a surprise<\/h3>\n
The new findings highlight the limits of current theoretical modeling of exoplanet atmospheres. Scientists had expected ammonia gas to dominate the upper atmosphere of Epsilon Indi Ab. They found ammonia, but less than anticipated. The best explanation \u2013 based on their analysis of the atmosphere \u2013 is the presence of water-ice clouds, they said.<\/p>\n
So the evidence for water-ice clouds came as a surprise to the researchers. The team used the Webb space telescope to analyze this distant world. <\/p>\n
The findings reveal a problem. Most current theoretical models of exoplanet atmospheres don\u2019t include clouds of any sort. That\u2019s because clouds make computing the data more complicated. So \u2013 because astronomers might not be looking for them \u2013 clouds could be missed in observations, even if they are there. As co-author James Mang at the University of Texas at Austin explained:<\/p>\n
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It\u2019s a great problem to have, and it speaks to the immense progress we\u2019re making thanks to the James Webb Space Telescope. What once seemed impossible to detect is now within reach, allowing us to probe the structure of these atmospheres, including the presence of clouds. <\/p>\n
This reveals new layers of complexity that our models are now beginning to capture, and opens the door to even more detailed characterization of these cold, distant worlds.<\/p>\n<\/blockquote>\n
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1\/4 New insights into a cold \u201cSuper-Jupiter\u201d: Using #JWST, we found evidence of water-ice clouds on Epsilon Indi Ab! This discovery shows that even cold gas giant atmospheres are far more complex than our current models suggest. ?Full press release: www.mpia.de\/news\/science\u2026<\/p>\n
\u2014 Max-Planck-Institut f\u00fcr Astronomie (@mpi-astro.bsky.social) 2026-04-22T13:48:04.184Z<\/p>\n<\/blockquote>\n
It\u2019s a step toward finding earthlike planets<\/h3>\n
The results are exciting not only in regards to exo-Jupiters. They are also a big step toward being able to find exoplanets that are more earthlike and might support life. Scientists have only recently been able start analyzing the atmospheres of these distant earthlike worlds more in-depth.<\/p>\n
This is easier for larger Jupiter-like planets. And in that group, it is the hot Jupiters that are easier to study. Cooler planets, more like Jupiter itself, require more sensitive instruments and longer observation times. So finding water-ice clouds on an exo-Jupiter is a great step. But finding such clouds on smaller earthlike planets might require more powerful telescopes. Lead author Elisabeth Matthews at the Max Planck Institute for Astronomy said:<\/p>\n
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JWST is finally allowing us to study solar-system analog planets in detail. If we were aliens, several light years away, and looking back at the sun, JWST is the 1st telescope that would allow us to study Jupiter in detail. For studying Earth in detail, we would need much more advanced telescopes, though.<\/p>\n<\/blockquote>\n
![\"Smiling](\"https:\/\/earthsky.org\/upl\/2026\/04\/Elisabeth-Matthews-Max-Planck-Institute-for-Astronomy.jpeg\")
Elisabeth Matthews at the Max Planck Institute for Astronomy in Germany is lead author of the new study about Epsilon Indi Ab. Image via Max Planck Institute for Astronomy.<\/figcaption><\/figure>\n What about cooler exo-Jupiters?<\/h3>\n
Even finding cooler exo-Jupiters is a challenge. By far most of the Jupiter-like worlds found so far are hot Jupiters. Those are gas giants like Jupiter, but orbit very close to their stars. As a result, they are extremely hot. That makes them easier to detect and study.<\/p>\n
But Jupiters farther from their stars are cooler, which makes them harder to find since they don\u2019t give off nearly as much heat or light. But in the case of Epsilon Indi Ab, the Webb telescope\u2019s Mid-Infrared Instrument (MIRI) was able to obtain direct images of the planet (albeit still just a bright dot). The coronagraph of the MIRI instrument blocks out the central star\u2019s light, enabling the fainter planet to be seen.<\/p>\n
Epsilon Indi Ab is about four times farther from its star than Jupiter is from the sun. It\u2019s also just a bit warmer than Jupiter, at 200 to 300 Kelvin (between \u201370 and +20 degrees Celsius or -94 to 68 Fahrenheit). Jupiter is around 140 K (-133 degrees C or -207 F). Why is Epsilon Indi Ab warmer? It\u2019s because there is still a lot of heat remaining inside it from when it 1st formed. But it\u2019s still much, much<\/em> cooler than hot Jupiters.<\/p>\n
NASA\u2019s upcoming Nancy Grace Roman Space Telescope will also be able to observe Epsilon Indi Ab. Roman will launch either later this year or in 2027. <\/p>\n
![\"Large](\"https:\/\/earthsky.org\/upl\/2025\/06\/hot-Jupiter-artist-illustration-October-13-2022.jpg\")
View larger. | Artist\u2019s illustration of a hot Jupiter type of exoplanet. Astronomers have found a lot of these. They\u2019re similar to Jupiter, but orbit close to their stars. So they\u2019re searingly hot in contrast to Epsilon Indi Ab, which orbits at some 30 AU \u2013 Neptune\u2019s distance from our sun \u2013 and so is much cooler. Image via ESO\/ M. Kornmesser.<\/figcaption><\/figure>\n Bottom line: A Jupiter-like exoplanet with water-ice clouds? NASA\u2019s Webb space telescope has found the 1st signs of cirrus-like clouds on exoplanet Epsilon Indi Ab.<\/p>\n
Source: A second visit to Eps Ind Ab with JWST: new photometry confirms ammonia and suggests thick clouds in the exoplanet atmosphere of the closest super-Jupiter<\/p>\n
Via Max Planck Institute for Astronomy<\/p>\n
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\n - The discovery was a surprise.<\/strong> Jupiter has ammonia gas in the upper atmosphere. But astronomers found less ammonia for Epsilon Indi Ab than anticipated. They surmise there must be water-ice clouds there instead.<\/li>\n