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GJ 251 c

GJ 251 · M3.0 V host star · cool red dwarf · main sequence

[ GJ_251_C.IMG ]
VIEW 1 · ON THE SURFACE
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Artist’s impression of GJ 251 c: VIEW 1 · ON THE SURFACE
VIEW 1 · ON THE SURFACE · Artist’s impression. No surface has been seen.
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18.2 light-years from Earth
[ FACTS.DAT ]
Right ascension / declination103.700° / 33.266°J2000 / ICRS
Gravity1.20 × Earthmodelled estimate
Year53.6 days
From its star0.1960 AUabout 29.3 million km
Stars in the system1 star2 known planets in system
Stars this world orbits1 starOrbits GJ 251
Day and nightLikely synchronous spinProbably spins once per orbit, keeping one hemisphere in permanent day and the other in permanent night. Heuristic: likely at ≤0.25 AU, uncertain to 0.50 AU, probably not beyond; rotation is not directly measured.
[ TEMP.EST ]MODELLED, NOT MEASURED
Host star≈3,450 Ktypical M3.0 V · 0.35 Sun radii
No atmosphere203 K · -70°C30% reflective · heat shared
Earth-like air236 K · -37°CBaseline plus 33°C

Star temperature and orbital distance set incoming energy, but stellar size is also required. This calculation uses a typical radius for the listed spectral type, 30% reflectivity and even heat redistribution. It is not a ground-temperature forecast: air, clouds, oceans and surface reflectivity could move the result by tens to hundreds of degrees. A likely synchronous spin also means the permanent day and night sides would not share one ground temperature.

[ STARLIGHT.SPC ]VISIBLE LIGHT ONLY

The marker above the bar is a typical temperature for this star’s class. The line below is Earth’s Sun.

red-orange

GJ 251 is class M3.0 V. Its visible daylight would be dim and strongly red-orange; most of its energy is infrared.

Representative lit-side geometry only. On a locked world, the star’s real elevation would depend on where you stand.

[ GROUND.TXT ]STILL INFERENCE

Most plausible case. A wider orbit than most nearby red-dwarf temperate planets: 0.20 AU and a 54-day year, receiving about 40% of Earth’s light. The star is 0.36 solar radii, so it still spans about 1.0°, twice the Sun’s width. Cold ground is the plausible case, rock and frost, with open water only under a greenhouse. The estimated radius near 1.8 Earth radii may mean a thicker volatile layer than a bare Earth, or just an uncertain mass.

Dry case. Cold rock. The flux is too low for a scorched day side unless the planet is much darker, and closer at times, than the circular orbit implies. The archive eccentricity is listed as zero.

Thick-air case. A CO₂-rich sky is the route to mild ground. It would also be the route to a hidden surface.

Walking. About 20% heavier than Earth, modelled. GJ 251 b is a small disk, about 0.15 of the Moon’s width. Daylight is dim, red, and only about 40% of Earth’s energy budget.

Based on: NASA composite; Teff 3342 K, R 0.36 Rsun, S 0.40, a 0.196 AU, estimated radius 1.8 Rearth

[ ORBIT.SYS ]2 KNOWN · ALL SHOWN
100% · Above 30°

GJ 251 c circles GJ 251. Also shown: GJ 251 b, each on its NASA-catalogued orbit. Use Higher and Lower to move your viewpoint above, through and below the orbital plane, and − / + to zoom. Orbit shapes and spacing are schematic.

[ SOURCES.TXT ]

Positions, distances, and system parameters come from the NASA Exoplanet Archive composite table, queried 25 Sep 2026. GJ 273 b uses the parallax in that row, 12.4 light-years. The 45 worlds follow Bohl, Lawrence, Lowry, and Kaltenegger.