List of potentially habitable exoplanets

This is a list of potentially habitable exoplanets and possible exoplanets. The list is based on estimates of habitability by the Habitable Exoplanets Catalog (HEC), and data from the NASA Exoplanet Archive. The HEC is maintained by the Planetary Habitability Laboratory at the University of Puerto Rico at Arecibo.[1]


Surface planetary habitability is thought to require orbiting at the right distance from the host star for liquid surface water to be present, in addition to various geophysical and geodynamical aspects, atmospheric density, radiation type and intensity, and the host star's plasma environment.[2]

Potential habitable zone status

In astronomy and astrobiology, the circumstellar habitable zone (CHZ or sometimes "ecosphere", "liquid-water belt", "HZ", "life zone" or "Goldilocks zone") is the region around a star where a planet with sufficient atmospheric pressure can maintain liquid water on its surface.[3][4]

A potentially habitable planet implies a terrestrial planet within the circumstellar habitable zone and with conditions roughly comparable to those of Earth (i.e. an Earth analog) and thus potentially favourable to Earth-like life. However, the question of what makes a planet habitable is much more complex than having a planet located at the right distance from its host star so that water can be liquid on its surface: various geophysical and geodynamical aspects, the radiation, and the host star's plasma environment can influence the evolution of planets and life, if it originated.[2]

In November 2013, astronomers reported, based on Kepler space mission data, that there could be as many as 40 billion Earth-sized planets orbiting in the habitable zones of Sun-like stars and red dwarfs in the Milky Way,[5][6] 11 billion of which may be orbiting Sun-like stars.[7]

A 2015 review concluded that the exoplanets Kepler-62f, Kepler-186f and Kepler-442b were likely the best candidates for being potentially habitable.[8] These are at a distance of 1,200, 490 and 1,120 light-years away, respectively. Of these, Kepler-186f is similar in size to Earth with a 1.2-Earth-radius measure and it is located towards the outer edge of the habitable zone around its red dwarf. The potentially habitable planet TOI 700 d is only 100 light years away.[9]

List from the Habitable Exoplanets Catalog

List of exoplanets in the conservative habitable zone

In astronomy and astrobiology, the circumstellar habitable zone (CHZ), or simply the habitable zone, is the range of orbits around a star within which a planetary surface can support liquid water given sufficient atmospheric pressure. Note that this does not ensure habitability, and that * represents an unconfirmed planet or planet candidate. Earth is included for comparison.[10]

ObjectStarStar typeMass (M⊕)Radius (R⊕)Flux (F⊕)Teq (K)Period (days)Distance (ly)Ref
EarthSun (Sol)G2V1.001.001.00255365.24-[10]
Proxima Centauri bProxima CentauriM6Ve≥1.30.8 – 1.1 – 1.40.6523411.1864.22[11]
Gliese 667 CcGliese 667 CM3V≥3.81.1 – 1.5 – 2.00.8827728.143 ± 0.02923.62[12][13]
Kepler-442bKepler-442K?V8.2 – 2.3 – 1.01.340.70233112.30531291.6[13]
Kepler-452bKepler-452G2V19.8 – 4.7 – 1.91.50, 1.631.11265+15
−13		384.81402[13][14]
Wolf 1061cWolf 1061M3V≥ 4.31.1 – 1.6 – 2.01.3627517.913.8[13]
Kepler-1229bKepler-1229M?V9.8 – 2.7 – 1.21.40.4921386.8769[13]
Kapteyn bKapteynsdM1≥ 4.81.2 - 1.6 - 2.10.4320548.613[13]
Kepler-62fKepler-62K2V10.2 – 2.8 – 1.21.410.39244267.2911200[13][15]
Kepler-186fKepler-186M1V4.7 – 1.5 – 0.61.170.29188129.9459561[13]
Luyten bLuyten's StarM3.5V3.15 - 2.89 - 2.63~1.35 1.06206-29318.65012.36[16]
TRAPPIST-1dTRAPPIST-1M8V0.300.781.042584.0539[17][18]
TRAPPIST-1eTRAPPIST-1M8V0.770.910.672306.139[17][18]
TRAPPIST-1fTRAPPIST-1M8V0.931.0460.382009.239[17][18]
TRAPPIST-1gTRAPPIST-1M8V1.151.150.2618212.439[17][18]
LHS 1140 bLHS 1140M4.5V6.61.430.462302540[19]
Kepler-1638b Kepler-1638G4V 45 – 6 – 1 1.60 1.17 304 259.365 2491.83 [20]
Teegarden cTeegarden's StarM7V1.110.3711.412.58[21]
Teegarden b*Teegarden's StarM7V1.051.154.9112.58[21]

List of exoplanets in the optimistic habitable zone

This is a list of the exoplanets that do not orbit within the conservative habitable zone but are still orbiting inside the wider boundaries of the optimistic habitable zone, and so are usually less likely to maintain surface liquid water.[22] Note that this does not ensure habitability, and that * represents an unconfirmed planet or planet candidate.

ObjectStarStar typeMass (M⊕)Radius (R⊕)Flux (F⊕)Teq (K)Period (days)Distance (ly)Ref
Kepler-296eKepler-296K7V12.5 – 3.3 – 1.41.51.22337.0±17.534.1737[13][23]
Kepler-62eKepler-62K2V18.7 – 4.5 – 1.91.61.10270±15122.41200[13][24]
Gliese 832 cGliese 832M2V≥ 5.41.2 – 1.7 – 2.21.00253; 233–28035.716[13]
K2-3dK2-3M0V11.11.51.4630044.6137[13][25]
Kepler-1544bKepler-1544K2V31.7 - 6.6 - 2.61.80.90248168.81138[13]
Kepler-283cKepler-283K5V35.3 – 7.0 – 2.81.80.9024892.71741[13]
Tau Ceti eTau CetiG8.5V≥ 3.931.1 – 1.6 – 2.01.6128516312[13]
Gliese 180 cGliese 180M2V≥ 6.41.3 – 1.8 – 2.30.7923924.338[13]
Kepler-440bKepler-440K6V41.2 – 7.7 – 3.11.91.43273101.1851[13]
Gliese 180 bGliese 180M2V≥ 8.31.3 – 1.9 – 2.41.2326817.438[13]
HD 40307 gHD 40307K2.5V≥ 7.11.3 – 1.8 – 2.30.68227197.842[13]
Gliese 163 cGliese 163M3.5V≥ 7.31.3 – 1.8 – 2.30.66230; 27725.649[13]
K2-18bK2-18M2.8V? – 16.5 – 6.02.20.94272±1532.9111[13][26]
Kepler-61bKepler-61K7V? – 13.8 – 5.22.21.27258, 273±1359.91063[13][27]
Kepler-443bKepler-443K3V? – 19.5 – 7.02.30.89247177.72540[13]
Kepler-22bKepler-22G5V? – 20.4 – 7.22.04; 2.41.11262289.9619[13][28]
Gliese 422 bGliese 422M3.5V≥ 9.91.4 – 2.0 – 2.60.6823126.241[13]
K2-9bK2-9M?V? – 16.8 – 6.12.21.38284±14, 314+67
−64		18.4359[13][29]
Gliese 3293 cGliese 3293M2.5V≥ 8.61.4 – 1.9 – 2.50.6022348.159[13]
Kepler-298dKepler-298K5V? – 26.8 – 9.12.51.2927177.51545[13]
Kepler-174dKepler-174K3V? – 14.8 – 5.52.20.43206247.41174[13]
Kepler-296fKepler-296K7V28.7 – 6.1 – 2.51.80.34198, 274.0±15.063.3737[13][30]
Gliese 682 cGliese 682M3.5V≥ 8.71.4 – 1.9 – 2.50.3719857.317[13]
KOI-4427 b*KOI-4427M0V38.5 – 7.4 – 3.01.80.24179147.7782[13]
Kepler-1090bKepler-1090K0V? – 16.8 – 6.12.31.20267198.72289[13]
Ross 128 bRoss 128M4V≥1.5~1.11.382809.8658 (± 0.0070)11.03[31]
HD 20794 e82 G. EridaniG8V4.77+0.96
−0.86		331.4120[32]
Gliese 625 bGliese 625M2V2.82±0.5114.62821.3[33]
HD 219134 g*HD 219134K3V>10.811.5 - 2.4 - 3.0?29894.221.35[34]

Previous candidates

HD 85512 b was initially estimated to be potentially habitable,[35][36] but updated models for the boundaries of the habitable zone placed the planet within the HZ,[37][38] and it is now considered non-habitable.[13]

Kepler-69c has gone through a similar process; though initially estimated to be potentially habitable,[39] it was quickly realized that the planet is more likely to be similar to Venus,[40] and is thus no longer considered habitable.[13]

Similarly, Tau Ceti f was initially considered potentially habitable,[41] but the improved model of the circumstellar habitable zone places the planet exterior to the outer limits of habitability, so it is now considered non-habitable.[13]

Kepler-438b was also initially considered potentially habitable, with highest ESI of 0.88; however, it was later found to be a subject of powerful flares that can strip a planet of its atmosphere, so it is now considered non-habitable. [13]

KOI-1686.01 was also considered a potentially habitable exoplanet after its detection in 2011, until proven a false positive by NASA in 2015.[42]

Notable exoplanets – Kepler Space Telescope
Confirmed small exoplanets in habitable zones.
(Kepler-62e, Kepler-62f, Kepler-186f, Kepler-296e, Kepler-296f, Kepler-438b, Kepler-440b, Kepler-442b)
(Kepler Space Telescope; 6 January 2015).[43]
Comparison of small planets found by Kepler in the habitable zone of their host stars.

See also

References
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