- TOI-199b is a Saturn-sized exoplanet 330 light-years from Earth.
- Not like most fuel giants, its temperature isn’t removed from Earth’s.
- New Webb observations revealed this world’s environment incorporates methane.
Saturn-sized exoplanet with Earth-like temperatures
Astronomers have used the James Webb Space Telescope to review an unusually heat, Saturn-sized exoplanet. The planet, TOI-199b, is about 330 light-years from Earth. It’s temperate, that means its temperature is just like Earth’s. It’s hotter than the fuel giants Jupiter and Saturn, however a lot cooler than hot Jupiters that orbit very near their stars.
This examine marked the primary shut take a look at the environment of a temperate fuel large. The researchers revealed on Could 20, 2026, that the planet’s environment incorporates methane. The observations additionally present hints of ammonia and carbon dioxide.
They used transmission spectroscopy to research the planet’s environment. That method can be utilized when the planet transits instantly between its star and the telescope on Earth.
The researchers published the peer-reviewed paper in The Astronomical Journal on Could 20, 2026.
Environment of a temperate Saturn-sized exoplanet
A lot of the large exoplanets astronomers know of thus far are sizzling Jupiters. They’re scorching sizzling since they orbit so near their stars. However there are some which might be extra temperate. That is the primary shut take a look at the environment of a temperate fuel large planet. As chief of the science group, Renyu Hu, affiliate professor of astronomy and astrophysics within the PennState Eberly Faculty of Science, explained:
One of many foremost benefits of research of planets past our photo voltaic system, often known as exoplanets, is the flexibility to review many various kinds of planets – particularly ones that we don’t see within the photo voltaic system – to study how planetary techniques type and evolve. For the reason that first exoplanet was found in 1992 by a group that included Aleksander Wolszczan at Penn State, astronomers have discovered hundreds of exoplanets. However just a few large, temperate exoplanets are identified and that is the primary time that now we have been in a position to examine the environment of one in all them intimately.
Environment Of Saturn-sized Planet With Earth-like Temperature Incorporates Methaneastrobiology.com/2026/05/atmo… #astrobiology #AbSciCon #AbSciCon26 #exoplanet
— Astrobiology (@astrobiology.bsky.social) 2026-05-21T17:36:26.219Z
An enormous world with Earth-like temperatures
TOI-199b is a fuel large, concerning the dimension of Saturn. Nevertheless it orbits far sufficient from its star that it’s not scorching sizzling like sizzling Jupiters. It’s far more average, about 80 levels Celsius (175 levels Fahrenheit). That’s nonetheless sizzling, however nowhere close to as sizzling as a sizzling Jupiter.
The best recorded temperature on Earth is about 57 levels Celsius (134 levels F). Because of this scientists take into account this planet to be temperate.
So how did the researchers decide the temperature and composition of TOI-199b’s environment? They used a method referred to as transmission spectroscopy. When the planet transits – passes in entrance of – its star as seen from Earth, Webb analyzes mild from the star because it passes by way of the planet’s environment. Devices on Webb then separate the star’s mild into its completely different elements. This gives clues concerning the the planet’s environment.
Altogether, Webb noticed the star for about 20 consecutive hours. Lead creator Aaron Bello-Arufe, a postdoctoral researcher at NASA’s Jet Propulsion Laboratory, stated:
As a planet passes in entrance of its star, a number of the star’s mild passes by way of the planet’s environment the place it interacts with the weather and molecules within the environment. Particular parts will take up particular wavelengths of sunshine, making a fingerprint within the spectrum of sunshine that JWST detects that displays the environment’s composition.
Spectrum reveals methane
Then, the researchers in contrast the spectrum to baseline measurements of the star’s mild. Any variations between the brand new transit spectra and the baseline will reveal what wavelengths of sunshine are being absorbed by the planet’s environment. And that tells you what the environment is made from. Bello-Arufe stated:
Once we in contrast the spectra throughout the transit to the baseline, we noticed that the environment blocked the wavelengths of starlight absorbed by methane. Fashions for the composition of temperate, gas-giant exoplanets had predicted that they might comprise methane, so it’s good to get affirmation that our theories are correct.
Extra observations wanted
The outcomes additionally trace at ammonia and carbon dioxide within the environment. However it’ll require extra observations to substantiate them. Hu stated:
With extra observations of this planet, we might set up the relative abundance of those varied gases in its environment. This extra full image of a temperate fuel large’s environment can then be used to enhance our fashions and doubtlessly higher perceive how planets and their atmospheres type and evolve, together with for Earth. The success of this primary examine of a temperate large planet’s environment additionally provides us confidence to dedicate extra assets and statement time to review different related planets. We will then see if this planet is exclusive or if there are normal shared traits for this sort of planet.
Saturn itself additionally has traces of methane in its environment. However this type of methane on fuel giants is primordial, not a results of life. Primordial gases are the gases current in a planet’s environment when it first shaped.
Jupiter, Uranus and Neptune have traces of methane of their atmospheres as properly. In reality, that’s what give Neptune its hanging bluish colour.
Backside line: TOI-199b is a heat Saturn-sized exoplanet 330 light-years away. New observations by the Webb area telescope present there’s methane in its environment.
Source: Methane on the Temperate Exo-Saturn TOI-199 b
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