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K2-3 d

K2-3 · M V host star · cool red dwarf · main sequence

[ K2_3_D.IMG ]
VIEW 1 · ON THE SURFACE
1 / 2
Artist’s impression of K2-3 d: VIEW 1 · ON THE SURFACE
VIEW 1 · ON THE SURFACE · Artist’s impression. No surface has been seen.
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143.7 light-years from Earth
[ FACTS.DAT ]
Right ascension / declination172.335° / -1.455°J2000 / ICRS
Gravity1.03 × Earthmodelled estimate
Year44.6 days
From its star0.2014 AUabout 30.1 million km
Stars in the system1 star3 known planets in system
Stars this world orbits1 starOrbits K2-3
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≈3,700 Ktypical M V · 0.50 Sun radii
No atmosphere257 K · -16°C30% reflective · heat shared
Earth-like air290 K · 17°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

K2-3 is class M 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 outer planet of K2-3, an early-M or late-K star of 0.55 solar radii, warmer than the mid-M hosts. From 0.20 AU the star spans about 1.4°, and the planet receives about 1.44 times Earth’s light. Radius 1.46 Earth radii. The mass is an upper limit, so the page’s 1.03 g is a model, not a weighing. Warm rock under an orange-red star, night-side ice only, a water patch under the star if the volatiles stayed.

Dry case. Warm oxidized rock and dunes. This flux supports a hot day side more easily than an ice cap.

Thick-air case. A volatile envelope fits a 1.5-radius world. Clouds could be the entire view.

Walking. Near Earth’s weight only in the model. K2-3 c is a small disk, about a quarter of the Moon’s width. The daylight is brighter and less deeply red than around a mid-M star. The system is 144 light-years away, magnitude 12.

Based on: Crossfield et al. 2015; Teff 3844 K, R 0.55 Rsun, S 1.44, e 0.09, Rp 1.46, a 0.20 AU. The archive mass is an upper limit.

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

K2-3 d circles K2-3. Also shown: K2-3 b, K2-3 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.