K2-125 is a cool M-dwarf (about 0.49 solar masses, 3,654 K, 0.40 solar radii), 124 light-years from Earth. K2-125 b is a planet with 2.2 Earth radii, with an orbital period of 21.8 days, at 0.121 AU from its star, on an eccentric orbit (e ≈ 0.08), discovered in 2017 via transit. The planet was found when it crossed the face of its star, producing periodic dips in brightness that reveal its size and orbital period to space-based photometry. K2-125 b orbits well inside Earth's distance from the Sun.