About this world
GJ 876 b is a gas giant orbiting GJ 876, a cool red dwarf (type M2.5V) 15.2 light-years from Earth. It is about 1.2 times the size of Jupiter (its size estimated from its mass) and holds 2.3 Jupiter masses. It completes an orbit every 61.1 days at 0.21 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 191 K (−83 °C), which places it in the conservative habitable zone: the band where liquid water could exist on a rocky surface. At its size it almost certainly keeps a deep envelope of hydrogen and helium.
It was discovered in 1998 by radial velocity with Multiple Observatories. The star wobbles toward and away from us, Doppler-shifting its spectrum. GJ 876 has 4 known planets; the others are GJ 876 d, GJ 876 c and GJ 876 e.