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K2-239 d

K2-239 · M3.0 V host star · cool red dwarf · main sequence

[ K2_239_D.IMG ]
VIEW 1 · ON THE SURFACE
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Artist’s impression of K2-239 d: VIEW 1 · ON THE SURFACE
VIEW 1 · ON THE SURFACE · Artist’s impression. No surface has been seen.
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101.4 light-years from Earth
[ FACTS.DAT ]
Right ascension / declination160.594° / 4.441°J2000 / ICRS
Gravity1.13 × Earthmodelled estimate
Year10.1 days
From its star0.0685 AUabout 10.2 million km
Stars in the system1 star3 known planets in system
Stars this world orbits1 starOrbits K2-239
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 atmosphere344 K · 71°C30% reflective · heat shared
Earth-like air377 K · 104°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

K2-239 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. The hot one in a packed trio. It receives about 3.4 times Earth’s light. The star spans about 2.8°. That is inner-edge territory: the day side is hot rock, not an eyeball of ice. Any water is steam or gone. The estimated radius is only 1.1 Earth radii, so a rocky body is plausible, but the mass is not measured.

Dry case. The likely case. Oxidized rock, no day-side ice, heat shimmer, a thin or stripped sky.

Thick-air case. A steam atmosphere or a molten-adjacent greenhouse. If a thick sky remains, you do not see the ground, and the surface may not be a place to stand.

Walking. About 13% heavier than Earth, modelled. K2-239 c would look about 0.9 of the Moon’s width, a real disk in the sky. The system is about 100 light-years away, star magnitude 15.

Based on: de Leon et al. 2023 area; NASA composite Teff 3420 K, R 0.36 Rsun, S 3.41, a 0.069 AU, Rp 1.1

[ ORBIT.SYS ]3 KNOWN · ALL SHOWN
100% · Above 30°

K2-239 d circles K2-239. Also shown: K2-239 b, K2-239 c, 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.