Emily Chan
A team of Canadian scientists used the James Webb Space Telescope (JWST) to reveal new insights into the atmosphere of an exoplanet orbiting a star in the constellation Pisces about 98 light-years away from Earth. The exoplanet is designated as GJ 9827 d, and the star is GJ 9827.
They found that the exoplanet’s atmosphere had a high concentration of heavier molecules, including a large quantity of water vapor. As a result, astronomers think the exoplanet could be a “steam world.”
Earlier in 2024, researchers examined data from the Hubble Space Telescope to help them detect water in the atmosphere of GJ 9827 d. It is about two times the size of Earth and is the smallest exoplanet with a confirmed atmosphere.
In the past, scientists focused on looking for atmospheres on large gas giants and planets around the size of Jupiter and Neptune. Until now, detecting atmospheres on smaller, Earth-sized planets has proven to be an elusive task.
“For now, all the planets we’ve detected that have atmospheres are giant planets, or at best mini-Neptunes,” said Caroline Piaulet-Ghorayeb, the lead author of the study and a Ph.D. candidate at Université de Montréal’s Trottier Institute for Research on Exoplanets.
“These planets have atmospheres made up mostly of hydrogen, making them more similar to gas giants in the solar system than to terrestrial planets like Earth, which have atmospheres dominated by heavier elements.”
GJ 9827 d is unique because of the composition of its atmosphere. It is richer with heavier molecules and water vapor, unlike the atmospheres of larger planets, which mostly consist of hydrogen.
According to Piaulet-Ghorayeb, the atmosphere of GJ 9827 d is closer in molecular weight to the carbon dioxide or nitrogen-dominated atmospheres that the researchers are looking for on smaller, rocky planets. These places are where they will eventually search for life.
The study authors discovered the “steam world” by making observations with the Near-Infrared Imager and Slitless Spectrograph on the JWST. They used transmission spectrography to analyze starlight passing through the exoplanet’s atmosphere in front of its host star, GJ 9827.
Sign up for Chip Chick’s newsletter and get stories like this delivered to your inbox.
