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Proxima Cen b

Proxima Cen · M5.5 V host star · cool red dwarf · main sequence

[ PROXIMA_B.IMG ]
VIEW 1 · FROM ORBIT
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Artist’s impression of Proxima Cen b: VIEW 1 · FROM ORBIT
VIEW 1 · FROM ORBIT · Artist’s impression. No surface has been seen.
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4.24 light-years from Earth
[ FACTS.DAT ]
Right ascension / declination217.393° / -62.676°J2000 / ICRS
Gravity1.01 × Earthmodelled estimate
Year11.2 days
From its star0.0485 AUabout 7.3 million km. α Cen A and α Cen B ≈13,000 AU from Proxima Cen; those two are 11.2–35.6 AU apart
Stars in the system3 stars2 known planets in system
Stars this world orbits1 starOrbits Proxima Cen; 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≈3,000 Ktypical M5.5 V · 0.16 Sun radii
No atmosphere240 K · -33°C30% reflective · heat shared
Earth-like air273 K · 0°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

Proxima Cen is class M5.5 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 red star about 1.6° across, roughly three times the Sun’s width from Earth, hangs fixed in the sky. The planet gets about 65% of Earth’s light, and most of that energy is infrared. Dark rock and dust under the star, with frost and ice pushed to the terminator and the night side. A small eyeball of slush or open water is possible directly under the star. The star flares often. No atmosphere has been seen.

Dry case. Oxidized rock and dust, no ice on the day side, heat shimmer, and a thin haze if any air remains. It would feel like a dim red desert, not an ice world.

Thick-air case. A thick atmosphere could hide the ground under cloud. Nothing in the data requires that sky. High CO₂ would warm the rock; you might see only a bright deck.

Walking. About Earth’s weight, from a minimum mass near 1.06 Earth masses, so the true weight could be higher. The light is dim and red. Proxima d, closer to the star, would look about a third the Moon’s width at best. Alpha Centauri A and B, 13,000 AU away, are two brilliant points, not disks.

Based on: Anglada-Escudé et al. 2016; NASA composite Teff 2900 K, R 0.141 Rsun, S 0.64, a 0.0485 AU

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

Proxima Cen b circles Proxima Cen alone. Proxima is about 13,000 AU from the Alpha Centauri A–B pair; A and B vary from 11.2 to 35.6 AU apart. Also shown: Proxima Cen d, 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.