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Kepler-186 f

Kepler-186 · M1 host star · cool red dwarf · existence disputed

[ KEPLER_186_F.IMG ]
VIEW 1 · ON THE SURFACE
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Artist’s impression of Kepler-186 f: VIEW 1 · ON THE SURFACE
VIEW 1 · ON THE SURFACE · Artist’s impression. No surface has been seen.
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579.2 light-years from Earth
[ FACTS.DAT ]
Right ascension / declination298.653° / 43.955°J2000 / ICRS
Gravity1.25 × Earthmodelled estimate
Year129.9 days
From its star0.4320 AUabout 64.6 million km
Stars in the system1 star5 known planets in system
Stars this world orbits1 starOrbits Kepler-186
Day and nightSpin state unknownIts rotation has not been measured, so we do not know whether it has a normal day/night cycle. 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 M1 · 0.50 Sun radii
No atmosphere176 K · -98°C30% reflective · heat shared
Earth-like air209 K · -65°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.

[ 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

Kepler-186 is class M1. Its visible daylight would be dim and strongly red-orange; most of its energy is infrared.

Representative daytime geometry only; the star’s height in the sky changes through the day.

[ GROUND.TXT ]STILL INFERENCE

Most plausible case. The famous outer planet, and a disputed one: later Kepler false-alarm work does not leave it as cleanly validated. If it is real, it receives only about 30% of Earth’s light around a 0.52-solar-radius star. The star spans about 0.65°, only a little larger than the Sun looks from Earth, because the orbit is a wide 0.43 AU. That is a cold, dim, orange-red sun in the sky, not a huge red disk. Ice and frost are the plausible ground. The 130-day orbit is far enough that a fixed dayside is not assured.

Dry case. Cold rock. A desert here is a frozen one, not a dune field in heat shimmer.

Thick-air case. A thick CO₂ atmosphere is the usual way people make this orbit habitable on paper. It would also hide the ground. No such sky has been seen.

Walking. About 25% heavier than Earth, modelled. The inner planets are tiny in this sky, a few hundredths of the Moon’s width. The star is magnitude 15, about 580 light-years away. The picture stands only if the signal is a planet.

Based on: Quintana et al. 2014; later Kepler reanalyses flag the validation as disputed; Teff 3755 K, R 0.52 Rsun, S 0.30, Rp 1.17, a 0.432 AU

[ ORBIT.SYS ]5 KNOWN · ALL SHOWN
100% · Above 30°

Kepler-186 f circles Kepler-186. Also shown: Kepler-186 b, Kepler-186 c, Kepler-186 d, Kepler-186 e, 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.