GJ 581 is a cool M-dwarf (about 0.29 solar masses, 3,500 K, 0.30 solar radii), 6.3 light-years from Earth. GJ 581 e is a 2.5-Earth-mass planet, with an orbital period of 3.1 days, at 0.028 AU from its star, discovered in 2009 via radial velocity. GJ 581 b is a 0.06-Jupiter-mass companion, with an orbital period of 5.4 days, at 0.040 AU from its star, discovered in 2005 via radial velocity. GJ 581 c is a 6.8-Earth-mass planet, with an orbital period of 12.9 days, at 0.072 AU from its star, discovered in 2007 via radial velocity.