Webb Telescope Reveals Sub-Neptune Atmospheric Secrets

The James Webb Space Telescope has enabled astronomers to analyze the atmosphere of sub-Neptune exoplanet TOI-421 b in unprecedented detail, due to its high temperature preventing haze and cloud formation. Webb’s observations detected water vapor, abundant hydrogen, and traces of gases like carbon monoxide and sulfur dioxide, but found no methane or carbon dioxide. This marks the first clear analysis of a sub-Neptune’s atmospheric composition, offering key insights into their formation and evolution. These results help explain why sub-Neptunes, the most common exoplanets, are absent from our solar system. The research highlights the unique capabilities of JWST in characterizing exoplanet atmospheres. This breakthrough advances our understanding of planetary diversity in the Milky Way.