GJ 251 c is a candidate super-Earth in the habitable zone of GJ 251, a red dwarf about 18 light-years away. The habitable zone is the range of distances where a planet could keep liquid water on its surface. GJ 251 c orbits every 53.6 days and has a minimum mass of about 3.8 Earth masses, which the discovery team describes as plausibly in the range of rocky planets.
It was reported in 2025 by a team led by Corey Beard. They used the radial velocity method, which detects the slight back-and-forth motion a planet's gravity gives its star, with new measurements from two instruments, the Habitable-zone Planet Finder and NEID, combined with archived data from Keck Observatory, CARMENES and SPIRou. A star's own activity can mimic a planet's signal, so the team compared how the signals behaved at different colours of light and tested more than 50 models of the planets and the star's activity before settling on their result. The same work refined the orbit and mass of the star's known inner planet, GJ 251 b, which circles every 14.2 days.
What makes GJ 251 c stand out is how close it is. The team noted that at about 5.5 parsecs, the next generation of 30-metre-class telescopes should be able to photograph rocky planets in GJ 251's habitable zone directly, and called GJ 251 c the best candidate in the northern sky for imaging a rocky, habitable-zone planet. They still describe it as a candidate. It has not been seen crossing in front of its star, so its size and true mass are unknown, and nothing is yet known about whether it has an atmosphere.