G 9-40 is a cool M-dwarf (about 0.30 solar masses, 3,395 K, 0.30 solar radii), 27.9 light-years from Earth. G 9-40 b is a 4.0-Earth-mass planet, with an orbital period of 5.7 days, at 0.042 AU from its star, and an equilibrium temperature near 441 K, discovered in 2019 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. G 9-40 b skims its star closer than Mercury orbits the Sun.