GJ 3634 is a cool M-dwarf (about 0.45 solar masses, 3,517 K, 0.43 solar radii), 20.4 light-years from Earth. GJ 3634 b is a 8.4-Earth-mass planet, with an orbital period of 2.6 days, at 0.029 AU from its star, on an eccentric orbit (e ≈ 0.08), discovered in 2010 via radial velocity. The planet betrayed itself through the star's reflex motion — a technique that first revealed worlds around Sun-like stars in the 1990s and remains a workhorse of exoplanet discovery. GJ 3634 b skims its star closer than Mercury orbits the Sun.