A planetary companion to a nearby M4 dwarf, Gliese 876

Doppler measurements of the M4 dwarf star Obese 876 taken at both Lick and Keck Observatories reveal periodic, Keplerian velocity variations with a pe riod of 61 days. The orbital fit implies that the companion has a mass of M = 2.1 M-JUP/sin i, an orbital eccentricity of e = 0.27 +/- 0.03, and a sem imajor axis of a = 0.21 AU. The planet is the first found around an M dwarf and was drawn from a survey of 24 such stars at Lick Observatory. It is th e closest extrasolar planet yet found, providing opportunities for follow-u p detection. The presence of a giant planet on a noncircular orbit, 0.2 AU from a 0.32 M. star, presents a challenge to planet formation theory. This planet detection around an M dwarf suggests that giant planets are numerous in the Galaxy.