GJ 876 and Its Four Worlds

GJ 876 is a small, cool red dwarf of spectral type M4, located 15.2 light-years away. Its mass is 0.37 solar masses and its radius is 0.376 solar radii, both smaller than the Sun's corresponding values, and its temperature of 3130 K is cooler than the Sun's. Four planets are known to orbit this star, all discovered by the radial velocity method, which detects the wobble a planet's gravity induces in its star's motion.

GJ 876 b, found in 1998, has a reported mass of 723 Earth masses, larger than Earth's and roughly 2.28 times Jupiter's mass, and the largest reported mass among the listed planets. Its orbital period is 61.1 days, the second-longest among these worlds. GJ 876 c, discovered in 2000, has a reported mass of 227 Earth masses and an orbital period of 30.1 days, the second-shortest among the listed planets.

The two remaining planets are less massive. GJ 876 d, discovered in 2005, has a reported mass of 6.83 Earth masses, the smallest among the listed planets, and completes an orbit in 1.94 days, the shortest period of the four. GJ 876 e, found in 2010, has a reported mass of 14.6 Earth masses, the second-smallest among the listed planets, and an orbital period of 124 days, the longest of the group.