JWST was launched into space on December 25, 2021, and started taking pictures and collecting data a few months later. Since the telescope has been fully operational, JWST has been observing the dark depths of our universe. On January 11, 2023, Kevin Stevenson and Jacob Lustig-Yaeger, both from the Johns Hopkins University Applied Physics Laboratory, announced that their team had discovered JWST’s first exoplanet.         

The exoplanet LHS 475 b is 41 light-years away from us in the constellation Octans. This constellation was suggested as an area of interest based on results from NASA’s Transiting Exoplanet Survey Satellite, a satellite whose main objective is to detect exoplanets around dwarf stars. JWST detected the exoplanet using its Near InfraRed Spectrograph (NIRSpec). The exoplanet is a rocky planet with a diameter of 99% of Earth’s diameter. LHS 475 b has a short orbital period around its red dwarf star — only two days — and is closer to the star than Mercury is to our Sun. This star, however, is cooler than our Sun, which means that there is some chance that LHS 475 b could have an atmosphere.

JWST is the only operating telescope that is capable of characterizing atmospheres on Earth-sized planets. While the transmission spectrum from LHS 475 b has not yet been fully analyzed, Stevenson and Lustig-Yaeger’s team has been able to start ruling out some compositions for its possible atmosphere. For example, they can be certain that it does not have a thick, methane-rich atmosphere similar to Saturn’s moon Titan. The planet is also a few hundred degrees warmer than Earth. This means that if clouds are detected, the planet may be more like Venus, with a carbon dioxide atmosphere. However, a 100% carbon dioxide atmosphere is very compact and more challenging to detect. In order to determine the difference between a pure carbon dioxide atmosphere and no atmosphere at all, more data will need to be collected. READ MORE