Researchers at the University of Chicago have developed a new method to determine if distant exoplanets possess atmospheres. This study, led by PhD student Qiao Xue and Professor Jacob Bean's group, promises a simpler and more efficient approach than previous techniques. The method holds potential for understanding atmosphere formation patterns when applied to more planets.
"When we look at a large enough data set, as we will this year with the James Webb Space Telescope, we are hoping to find trends to help us understand more about atmosphere formation—and what makes planets habitable," said Xue.
Atmospheres play a crucial role in making planets habitable by insulating them and regulating their temperatures. However, directly imaging rocky, Earth-like exoplanets close to their stars is challenging. Scientists rely on clues such as light fluctuations as planets orbit their host stars.
The new method uses temperature differences between an exoplanet's hottest side and its theoretical maximum temperature. Atmospheres disperse heat around the planet's surface, reducing the temperature of the side facing the star directly. If an exoplanet's actual temperature is lower than expected, it may indicate an atmosphere.
The precision required for these measurements was previously unattainable until the advent of the James Webb Space Telescope. This telescope allows scientists to record planetary temperatures by measuring emitted energy intensity in infrared wavelengths.
Xue applied this technique to planet GJ1132 b and concluded it lacks an atmosphere due to its measured temperature being too close to its calculated maximum temperature. "It is therefore not a suitable candidate for life," she stated.
While other methods exist for detecting exoplanetary atmospheres, Xue emphasized that this approach is less prone to false results compared to techniques that measure light filtering through atmospheres—a process complicated by stellar activity and cloud presence.
"This study was exciting because I finally got a chance to work with rocky planets, which are the dream subject of every exoplanet scientist because they have so much potential for life," Xue added. "Now I'm so excited to see what comes next."
The research involved contributions from other UChicago authors Jacob Bean, Michael Zhang, Edwin Kite, and collaborators from various institutions including Harvard and Smithsonian Center for Astrophysics, Cornell University, University of Arizona, and Peking University in China.
This study was published in Astrophysical Journal Letters on September 13, 2024, under the title "JWST Thermal Emission of the Terrestrial Exoplanet GJ 1132b." Funding was provided by Heising-Simons Foundation, NASA, and Alfred P. Sloan Foundation.