The star has a transiting
exoplanet, called
K2-18b, a
super-Earth located within the
habitable zone of K2-18. to have its atmosphere characterized; initially thought to contain
water vapor, more recent observations have instead detected
methane and
carbon dioxide. The presence of these molecules and non-detection of
ammonia is consistent with predictions for a
hycean planet. A second, non-transiting planet, K2-18c, was discovered in 2017 by
radial velocity with
HARPS. This planet was challenged by another team with
CARMENES data, but its existence was reaffirmed by the discovery team based on both HARPS and CARMENES data. This planet has also been confirmed by a later independent study. System tidal simulation suggests that K2-18c is a gas-rich, Neptune-like planet, similar to K2-18b. == References ==