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K2-288 B b

K2-288 B · M3 V host star · cool red dwarf · main sequence

[ K2_288_B_B.IMG ]
VIEW 1 · ON THE SURFACE
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Artist’s impression of K2-288 B b: VIEW 1 · ON THE SURFACE
VIEW 1 · ON THE SURFACE · Artist’s impression. No surface has been seen.
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214 light-years from Earth
[ FACTS.DAT ]
Right ascension / declination55.444° / 18.268°J2000 / ICRS
Gravity1.18 × Earthmodelled estimate
Year31.4 days
From its star0.1640 AUabout 24.5 million km. K2-288 A ≈55 AU projected from K2-288 B
Stars in the system2 stars1 known planet in system
Stars this world orbits1 starOrbits K2-288 B; not circumbinary
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 V · 0.35 Sun radii
No atmosphere222 K · -51°C30% reflective · heat shared
Earth-like air255 K · -18°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

K2-288 B is class M3 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. The planet orbits the smaller star of a binary, K2-288 B, an M3 star of 0.32 solar radii. It receives only about 44% of Earth’s light, and the star spans about 1.0°. Radius about 1.9 Earth radii, which often means a volatile envelope rather than bare rock, though the mass is not measured. Cold ground if the surface is solid: rock and frost. The other star, K2-288 A, is about 55 AU away in projection and would be a brilliant point, not a second sun.

Dry case. Cold rock. A hot desert does not fit 44% of Earth’s light.

Thick-air case. The 1.9-radius estimate makes a cloudy envelope the more common outcome for planets of this size. The ground may not be visible, and may not be rock.

Walking. About 18% heavier than Earth only in a mass-radius model that assumes rock. If the planet is puffy, you are not walking on that model. No sibling planet is known. The system is about 214 light-years away.

Based on: Feinstein et al. 2019; planet orbits the M3 secondary; Teff 3341 K, R 0.32 Rsun, S 0.44, Rp 1.9, a 0.164 AU; binary projected separation about 55 AU

[ ORBIT.SYS ]1 KNOWN · ALL SHOWN
100% · Above 30°

K2-288 B b circles K2-288 B alone. K2-288 A and B are separated by about 55 AU in projection. 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.