Overview

• TOI-421 b, located 245 light-years away, has a clear atmosphere free of haze and clouds, confirmed through Webb's advanced infrared spectroscopy.
• The planet's atmosphere contains water vapor, carbon monoxide, and sulfur dioxide, but lacks methane and carbon dioxide, aligning with predictions for hot exoplanets above 1,070°F.
• TOI-421 b’s hydrogen-rich atmosphere mirrors the composition of its Sun-like host star, differing from cooler sub-Neptunes that feature heavier molecules.
• This discovery challenges prior assumptions about sub-Neptune formation and suggests a potential link between atmospheric clarity and equilibrium temperature.
• Researchers aim to study additional hot sub-Neptunes to determine if TOI-421 b represents a broader trend or is an outlier in its class.