Exoplanet Atmospheres: Transit Signatures, Composition, and Habitability Clues

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Planets outside our solar system orbit stars and have atmospheres whose gases—like hydrogen, helium, methane, carbon dioxide, and water vapor—shape their temperature and whether liquid water could exist, and scientists study them by analyzing how starlight filters through or reflects from the atmosphere, with recent discoveries of water vapor on K2-18b and TOI-700d and even complex organic molecules showing how varied these worlds can be.