Proxima Cen is a cool M-dwarf (about 0.12 solar masses, 2,900 K, 0.14 solar radii), 4.2 light-years from Earth. Proxima Centauri is the nearest star to the Sun. Proxima b is an Earth-mass planet in the habitable zone. Proxima Cen d is a 0.3-Earth-mass planet, with an orbital period of 5.1 days, at 0.029 AU from its star, and an equilibrium temperature near 282 K, discovered in 2025 via radial velocity.