K2-18 is a cool M-dwarf (about 0.36 solar masses, 3,457 K, 0.41 solar radii), 38.0 light-years from Earth. K2-18 b is a temperate sub-Neptune in the habitable zone of a red dwarf and one of the most observed small-planet atmospheres with JWST. K2-18 c is a 7.5-Earth-mass planet, with an orbital period of 9.0 days, at 0.060 AU from its star, and an equilibrium temperature near 363 K, on an eccentric orbit (e ≈ 0.47), discovered in 2017 via radial velocity. K2-18 b is a 8.9-Earth-mass planet, with an orbital period of 32.9 days, at 0.143 AU from its star, and an equilibrium temperature near 284 K, on an eccentric orbit (e ≈ 0.20), discovered in 2015 via transit.