Gliese 876 b was the first planet discovered orbiting a red dwarf. The discovery, announced in June 1998, marked an important early step in finding planets around stars much smaller and cooler than the Sun.
Astronomers detected Gliese 876 b through the radial-velocity method. As the planet orbits, its gravity makes the host star move slightly back and forth, shifting the star’s spectral lines through the Doppler effect. Teams using the Keck and Lick observatories, and independently the Geneva Extrasolar Planet Search team, identified the signal.
Gliese 876 is a red dwarf, also called an M dwarf: a low-mass star that is cooler and far less luminous than the Sun. The planet completes an orbit in about 61 days. A common mix-up is confusing “first planet around a red dwarf” with the first exoplanet ever discovered; that distinction belongs to the pulsar planets found around PSR B1257+12 in 1992, while 51 Pegasi b was the first around a Sun-like star.