- \n
- TOI-561 b is a hot, rocky super-Earth<\/strong> exoplanet 560 light-years from Earth. Does it have an atmosphere?<\/li>\n
- New observations by the James Webb Space Telescope<\/strong> show it has an atmosphere that is a lot denser than expected. It is also likely covered in an ocean of magma.<\/li>\n
- A dense atmosphere was unexpected,<\/strong> because the planet is broiling hot on its dayside and orbits so close to its star. How does it keep its atmosphere?<\/li>\n<\/ul>\n
EarthSky\u2019s 2026 lunar calendar is available now. Get yours today! Makes a great gift.<\/p>\n
A dense atmosphere on lava planet TOI-561 b<\/h3>\n
Astronomers have discovered many rocky exoplanets orbiting other stars. If the rocky worlds in our solar system are any indication, some of them should have atmospheres. Now, a team of researchers led by the Carnegie Institution for Science (Carnegie Science) in Washington, D.C, has found what they say is the best evidence yet for a rocky exoplanet with an atmosphere. On December 10, 2025, the researchers said the planet \u2013 TOI-561 b \u2013 is a scorching hot super-Earth that orbits close to its star. The planet is likely covered in an ocean of magma and has a thick, volatile-rich atmosphere. The finding is surprising, because scientists thought the planet was too small and hot to have retained an atmosphere.<\/p>\n
The researchers used NASA\u2019s James Webb Space Telescope for their observations.<\/p>\n
TOI-561 b, about 560 light-years away, is a super-Earth, meaning it\u2019s larger than Earth but smaller than Neptune. Its radius is 1.4 times Earth\u2019s, and its mass is about twice that of Earth\u2019s. Scientists also found it\u2019s significantly lower in density than Earth. The presence of a thick atmosphere could help explain that. The planet\u2019s star, TOI-561, is similar to but slightly smaller than our sun.<\/p>\n
In 2024, astronomers also announced that another super-Earth, 55 Cancri e, might have an atmosphere of carbon dioxide or carbon monoxide. And like TOI-561 b, it also orbits close to its star and might have a molten surface. It\u2019s 41 light-years away.<\/p>\n
The researchers published their peer-reviewed results in The Astrophysical Journal Letters<\/em> on December 11, 2025.<\/p>\n
\n
A Carnegie-led team of astronomers has reported the strongest evidence yet for an atmosphere on a rocky exoplanet\u2014and it’s in a place no one expected. (?)? carnegiescience.edu\/ultra-hot-lava-world-has-thick-atmosphere-upending-expectations<\/p>\n
\u2014 Carnegie Science (@carnegiescience.bsky.social) 2025-12-15T18:44:38.643Z<\/p>\n<\/blockquote>\n
\n
#NASAWebb has detected a thick blanket of gas surrounding the distant lava world TOI-561 b, challenging the idea that small planets so close to their stars are not able to sustain atmospheres: ? ? <\/p>\n
\u2014 Space Telescope Science Institute (@stsci.edu) 2025-12-11T15:12:04.355529393Z<\/p>\n<\/blockquote>\n
Surprise! TOI-561 b has an atmosphere<\/h3>\n
TOI-561 b orbits very close to its star, completing an orbit in only 10.56 hours. As a result, it is broiling hot. Scientists thought the planet was too small and too hot to hold onto an atmosphere. But the researchers were in for a surprise. Nicole Wallack, the second author of the new paper at Carnegie, said:<\/p>\n
\n
Based on what we know about other systems, astronomers would have predicted that a planet like this is too small and hot to retain its own atmosphere for long after formation. But our observations suggest it is surrounded by a relatively thick blanket of gas, upending conventional wisdom about ultra-short-period planets.<\/p>\n<\/blockquote>\n
In our own solar system, Mercury \u2013 which orbits further from the sun than TOI-561 b orbits its star \u2013 only has an extremely thin exosphere, not a true atmosphere. Yet somehow TOI-561 b has been able to hold onto a dense atmosphere.<\/p>\n
![\"Partial](\"https:\/\/earthsky.org\/upl\/2025\/12\/TOI-561-b-atmosphere-artist-concept-NASA-December-11-2025.jpeg\")
View larger. | Artist\u2019s concept of a dense atmosphere above a magma ocean on TOI-561 b. Image via NASA\/ ESA\/ CSA\/ Ralf Crawford (STScI).<\/figcaption><\/figure>\n Unusual low density<\/h3>\n
Scientists knew that TOI-561 b also had an unusually low density. They surmised that a thick atmosphere might help explain that mystery. That would make the planet appear to be larger but less dense than it really was. As lead author Johanna Teske at Carnegie Science explained:<\/p>\n
\n
It\u2019s not what we call a super-puff, or \u2018cotton candy\u2019 planet, but it is less dense than you would expect if it had an Earth-like composition.<\/p>\n<\/blockquote>\n
The researchers also hypothesized that TOI-561 b might have a smaller rocky core and a mantle that is less dense than Earth\u2019s. Teske said:<\/p>\n
\n
TOI-561 b is distinct among ultra-short period planets in that it orbits a very old \u2013 twice as old as the sun \u2013 iron-poor star in a region of the Milky Way known as the thick disk. It must have formed in a very different chemical environment from the planets in our own solar system.<\/p>\n<\/blockquote>\n
![\"Smiling](\"https:\/\/earthsky.org\/upl\/2025\/12\/Johanna-Teske-Carnegie-Science.jpg\")
Scientist Johanna Teske at Carnegie Science is the lead researcher in the new study about TOI-561 b and its surprisingly dense atmosphere. Image via Carnegie Science.<\/figcaption><\/figure>\n Looking for an atmosphere<\/h3>\n
But it was still difficult to explain the results based on the planet\u2019s composition alone. So could it really have a thick atmosphere?<\/p>\n
The researchers used the Near-Infrared Spectrograph (NIRSpec) instrument on the James Webb Space Telescope to search for signs of an atmosphere. They did this by measuring the temperature of the planet on its dayside in near-infrared (TOI-561 b is tidally locked to its star, so the same side always faces the star).<\/p>\n
In theory, if the planet had no atmosphere, then the temperature on its surface should be around 4,900 degrees Fahrenheit (2,700 degrees Celsius). But it was actually a lot cooler, about 3,200 degrees Fahrenheit (1,760 degrees Celsius). That\u2019s still scorching hot of course, but much cooler than expected.<\/p>\n
Narrowing down the possibilities<\/h3>\n
The team posited various possibilities. The magma ocean would circulate some heat, but the lava would be solid on the colder nightside of the planet. That would limit heat flow from the dayside. A thin rock vapor atmosphere was also possible. But it probably wouldn\u2019t produce as much cooling as Webb had observed.<\/p>\n
The other, and best, option is a thick atmosphere composed of volatiles like water, oxygen and carbon dioxide. Volatiles are compounds that can easily vaporize. Co-author Anjali Piette at the University of Birmingham in the U.K. explained it this way:<\/p>\n
\n
We really need a thick volatile-rich atmosphere to explain all the observations. Strong winds would cool the dayside by transporting heat over to the nightside. Gases like water vapor would absorb some wavelengths of near-infrared light emitted by the surface before they make it all the way up through the atmosphere. (The planet would look colder because the telescope detects less light.) It\u2019s also possible that there are bright silicate clouds that cool the atmosphere by reflecting starlight.<\/p>\n<\/blockquote>\n
![\"Graph](\"https:\/\/earthsky.org\/upl\/2025\/12\/TOI-561-b-spectrum-NASA-December-11-2025.jpg\")
View larger. | Emission spectrum of TOI-561 b from the James Webb Space Telescope. The data are consistent with an atmosphere rich in volatiles like water, oxygen and carbon dioxide. The model shown here assumes an atmosphere that is composed of 100% water vapor. Image via NASA\/ ESA\/ CSA\/ Ralf Crawford (STScI); Science: Johanna Teske (Carnegie Science Earth and Planets Laboratory)\/ Anjali Piette (University of Birmingham)\/ Tim Lichtenberg (Groningen)\/ Nicole Wallack (Carnegie Science Earth and Planets Laboratory).<\/figcaption><\/figure>\n How did TOI-561 b keep its atmosphere?<\/h3>\n
The question remains, however: How was TOI-561 b able to maintain a thick atmosphere? As co-author Tim Lichtenberg at the University of Groningen in the Netherlands postulated:<\/p>\n
\n
We think there is an equilibrium between the magma ocean and the atmosphere. At the same time that gases are coming out of the planet to feed the atmosphere, the magma ocean is sucking them back into the interior. This planet must be much, much more volatile-rich than Earth to explain the observations. It\u2019s really like a wet lava ball.<\/p>\n<\/blockquote>\n
As is often the case, the findings bring new questions to contemplate. As Teske noted:<\/p>\n
\n
What\u2019s really exciting is that this new data set is opening up even more questions than it\u2019s answering.<\/p>\n<\/blockquote>\n
Bottom line: Astronomers have found evidence for a thick atmosphere on lava planet TOI-561 b. It\u2019s a broiling hot super-Earth world 560 light-years from Earth.<\/p>\n
Source: A Thick Volatile Atmosphere on the Ultrahot Super-Earth TOI-561 b<\/p>\n
Via Carnegie Science<\/p>\n
Via NASA<\/p>\n
Read more: Researchers question methane atmosphere on TRAPPIST-1e<\/p>\n
Read more: Possible atmosphere on rocky exoplanet found for 1st time<\/p>\n
<\/div>\n
\n - New observations by the James Webb Space Telescope<\/strong> show it has an atmosphere that is a lot denser than expected. It is also likely covered in an ocean of magma.<\/li>\n