Kepler-421 is a Sun-like G-type star (about 0.79 solar masses, 5,308 K, 0.76 solar radii), 349 light-years from Earth. Kepler-421 b is a planet with 4.2 Earth radii, with an orbital period of 1.93 years, at 1.219 AU from its star, and an equilibrium temperature near 185 K, discovered in 2014 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. Kepler-421 b orbits at roughly the distance of Mars from the Sun.