About this world
GJ 251 c is a super-Earth orbiting GJ 251, a cool red dwarf (type M3.0V) 18.2 light-years from Earth. It is about 1.8 times the size of Earth (its size estimated from its mass), with at least 3.9 Earth masses (a minimum, measured by radial velocity). It completes an orbit every 53.6 days at 0.2 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 216 K (−57 °C), which places it in the conservative habitable zone: the band where liquid water could exist on a rocky surface. By the "cosmic shoreline", it has likely held on to an atmosphere.
It was discovered in 2025 by radial velocity with Multiple Observatories. The star wobbles toward and away from us, Doppler-shifting its spectrum. GJ 251 has 2 known planets; the others are GJ 251 b.