13point8100 ly map
2 known planets · 18.2 light years

GJ 251

GJ 251 is a red dwarf (M3.0 V) 18.2 light years away, with 2 confirmed planets, 1 of them in the habitable zone. Distances and orbital speeds are to scale; the star and planets are enlarged so you can see them.

Day 0
habitable zone (estimate)planet orbits

Green band: where liquid water could exist on a planet's surface. Drag to turn the system, pinch or scroll to zoom.

The star

The star

GJ 251

Type
M3.0 V
Surface
≈ 3,342 K
Size
0.36 × the Sun
Mass
0.35 × the Sun
Brightness
0.0155 × the Sun
Habitable zone
0.102–0.267 AU

The planets

GJ 251

GJ 251 b

Year
14.24 days
Distance from star
0.0808 AU
Mass
at least 3.9 Earths
Size
1.8 × Earth
Temperature
≈ 336 K (+63 °C)
Found
2020, radial velocity (W. M. Keck Observatory)
Outside the habitable zone
GJ 251

GJ 251 c

Year
53.65 days
Distance from star
0.196 AU
Mass
at least 3.9 Earths
Size
1.8 × Earth
Temperature
≈ 216 K (-57 °C)
Found
2025, radial velocity (Multiple Observatories)
In the habitable zone

Masses found by the wobble method are minimums, because the orbit's tilt is unknown. Temperatures are equilibrium estimates for a bare planet, before any atmosphere.

How we know

The wobble

The planet tugs its star back and forth. Spectrographs measure the tiny shift in the star's light, which gives the planet's year and a minimum mass.

Sources

  1. Planet and star parameters: NASA Exoplanet Archive, Planetary Systems Composite Parameters, retrieved 31 Oct 2026. This research has made use of the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with NASA under the Exoplanet Exploration Program.
  2. Position: HYG Database v4.1 (CC BY-SA 4.0).
  3. Habitable zone: a simple estimate from the star's brightness (√L × 0.95 to 1.67 AU), shown as a guide.
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