A Canadian-led international study has revealed new insights into the atmosphere of GJ 9827 d -- an exoplanet orbiting the star GJ 9827 in the constellation Pisces, about 98 light-years from Earth -- using the James Webb Space Telescope (JWST).
The study found that the planet's atmosphere contains a high concentration of heavier molecules, including a significant amount of water vapor, making astronomers think it could very well be a "steam world."
Published in The Astrophysical Journal Letters, the study was led by Caroline Piaulet-Ghorayeb, a Ph.D. candidate at Université de Montréal's Trottier Institute for Research on Exoplanets (IREx), in collaboration with researchers worldwide.
Earlier this year, using Hubble Space Telescope (HST) data, IREx researchers announced they'd detected water in the atmosphere of GJ 9827 d, making it, at roughly two times the size of the Earth, the smallest exoplanet with a confirmed atmosphere.
Together, these significant findings open new avenues for the search for life beyond our solar system and enhance our understanding of planetary formation and composition.
For years, scientists have focused on the detection of atmospheres on large gas giants and mini-Neptunes -- planets much larger than Earth and with atmospheres dominated by hydrogen, like Jupiter and Neptune in our solar system.
But until now, detecting atmospheres around smaller planets, closer to Earth-sized, has remained an elusive goal.
What sets GJ 9827 d apart is its atmosphere's composition. By combining JWST/NIRISS and HST data, Piaulet-Ghorayeb showed that, unlike the hydrogen-dominated atmospheres of larger planets, GJ 9827 d's is rich in heavier molecules, with quite a bit of water vapor.
This discovery marks the first robust detection of an exoplanet atmosphere where hydrogen is not the dominant component, suggesting instead a heavier, water-rich atmosphere.
While GJ 9827 d itself is not thought to be habitable due to its proximity to its host star and resulting high surface temperatures (around 350°C), the discovery is a major leap forward in the search for habitable environments.
Further planned JWST observations of GJ 9827 d in the coming months could shed more light on the components of its steam atmosphere, the astronomers hope.