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 of 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.

List from the Habitable Exoplanets Catalog

List of exoplanets in the conservative habitable zone

This is a list of the exoplanets that are more likely to have a rocky composition (which according to current research[9][10] requires a radius of less than 1.6 R⊕ and a mass less than 6 M⊕) and maintain surface liquid water (i.e. between 0.5 and 1.5 R⊕ and between 0.1 and 5 M⊕, and orbiting within the conservative habitable zone). Note that this does not ensure habitability, and that * represents an unconfirmed planet or planet candidate. Earth is included for comparison.

ObjectStarStar typeMass (M⊕)Radius (R⊕)Flux (F⊕)Teq (K)Period (days)Distance (ly)Ref
EarthSun (Sol)G2V1.001.001.00255365.24-
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 – 2.00.6022317.913.8[13]
Kepler-1229bKepler-1229M?V9.8 – 2.7 – 1.21.40.4921386.8769[13]
Kapteyn b*KapteynsdM1≥ 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 - 2.631.06206-29318.65012.36[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 1140M?V6.61.430.462302540[19]
Kepler-1638b Kepler-1638G4V 45 – 6 – 1 1.60 1.17 304 259.365 2491.83 [20]

List of exoplanets in the optimistic habitable zone

This is a list of the exoplanets that are less likely to have a rocky composition or maintain surface liquid water (i.e. 0.5 < planet's radius ≤ 1.5 Earth radii or 0.1 < planet's minimum mass ≤ 10 Earth masses, or the planet is orbiting within the optimistic habitable zone). 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-438bKepler-438M?V4.0 – 1.3 – 0.61.11.3827635.2473[13]
Kepler-296eKepler-296M?V12.5 – 3.3 – 1.41.51.22337.0±17.534.1737[13][21]
Kepler-62eKepler-62K2V18.7 – 4.5 – 1.91.61.10270±15122.41200[13][22]
Gliese 832 cGliese 832M2V≥ 5.41.2 – 1.7 – 2.21.00253; 233–28035.716[13]
K2-3dK2-3M?V11.11.51.4630044.6137[13][23]
Kepler-1544bKepler-1544K?V31.7 - 6.6 - 2.61.80.90248168.81138[13]
Kepler-283cKepler-283K?V35.3 – 7.0 – 2.81.80.9024892.71741[13]
Tau Ceti e*Tau CetiG8.5V≥ 4.31.1 – 1.6 – 2.01.51282168.112[13]
Gliese 180 cGliese 180M2V≥ 6.41.3 – 1.8 – 2.30.7923924.338[13]
Kepler-440bKepler-440K?V41.2 – 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]
K2-18bK2-18M?V? – 16.5 – 6.02.20.94272±1532.9111[13][24]
Kepler-61bKepler-61K7V? – 13.8 – 5.22.21.27258, 273±1359.91063[13][25]
Kepler-443bKepler-443K?V? – 19.5 – 7.02.30.89247177.72540[13]
Kepler-22bKepler-22G5V? – 20.4 – 7.22.04; 2.41.11262289.9619[13][26]
Gliese 422 b*Gliese 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][27]
Gliese 3293 cGliese 3293M2.5V≥ 8.61.4 – 1.9 – 2.50.6022348.159[13]
Kepler-298dKepler-298K?V? – 26.8 – 9.12.51.2927177.51545[13]
Kepler-174dKepler-174K?V? – 14.8 – 5.52.20.43206247.41174[13]
Kepler-296fKepler-296M?V28.7 – 6.1 – 2.51.80.34198, 274.0±15.063.3737[13][28]
Gliese 682 cGliese 682M3.5V≥ 8.71.4 – 1.9 – 2.50.3719857.317[13]
KOI-4427 b*KOI-4427M?V38.5 – 7.4 – 3.01.80.24179147.7782[13]
Kepler-1090bKepler-1090G?V? – 16.8 – 6.12.31.20267198.72289[13]
Ross 128 bRoss 128M4V≥1.5~1.11.382809.8658 (± 0.0070)11.03[29]
HD 20794 e*82 G. EridaniG8V4.77+0.96
−0.86		331.4120[30]
Gliese 625 bGliese 625M2V2.82±0.5114.62821.3[31]
HD 219134 g*HD 219134K3V>10.811.5 - 2.4 - 3.0?29894.221.35[32]

Previous candidates

HD 85512 b was initially estimated to be potentially habitable,[33][34] but updated models for the boundaries of the habitable zone placed the planet within the HZ,[35][36] and it is now considered non-habitable.[13] Kepler-69c has gone through a similar process; though initially estimated to be potentially habitable,[37] it was quickly realized that the planet is more likely to be similar to Venus,[38] and is thus no longer considered habitable.[13]

Similarly, Tau Ceti f was initially considered potentially habitable,[39] 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]

KOI-1686.01 was also considered a potentially habitable exoplanet after its detection in 2011, until proven a false positive by NASA in 2015.[40]

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).[41]
Comparison of small planets found by Kepler in the habitable zone of their host stars.

See also

References

  1. ↑ "Habitable Exoplanets Catalog". University of Puerto Rico at Arecibo. 2015. Retrieved 3 June 2015.
  2. 1 2 Lammer, H.; Bredehöft, J. H.; Coustenis, A.; Khodachenko, M. L.; et al. (2009). "What makes a planet habitable?" (PDF). The Astronomy and Astrophysics Review. 17: 181–249. Bibcode:2009A&ARv..17..181L. doi:10.1007/s00159-009-0019-z. Archived from the original (PDF) on 2016-06-02. Retrieved 2016-05-03.
  3. ↑ "VPL Glossary". washington.edu.
  4. ↑ "The Goldilocks Zone". NASA. 2 October 2003.
  5. ↑ Overbye, Dennis (4 November 2013). "Far-Off Planets Like the Earth Dot the Galaxy". New York Times. Retrieved 5 November 2013.
  6. ↑ Petigura, Erik A.; et al. (31 October 2013). "Prevalence of Earth-size planets orbiting Sun-like stars". Proceedings of the National Academy of Sciences of the United States of America. 110: 19273–19278. arXiv:1311.6806. Bibcode:2013PNAS..11019273P. doi:10.1073/pnas.1319909110. PMC 3845182. PMID 24191033. Retrieved 5 November 2013.
  7. ↑ Khan, Amina (4 November 2013). "Milky Way may host billions of Earth-size planets". Los Angeles Times. Retrieved 5 November 2013.
  8. ↑ Gilster, Paul; LePage, Andrew (30 January 2015). "A Review of the Best Habitable Planet Candidates". Centauri Dreams, Tau Zero Foundation. Retrieved 24 July 2015.
  9. ↑ Gilster, Paul; LePage, Andrew (14 November 2014). "The Transition from Rocky to Non-Rocky Planets". Centauri Dreams, Tau Zero Foundation. Retrieved 17 October 2017.
  10. ↑ LePage, Andrew (3 January 2015). "The Composition of Super-Earths". Drew Ex Machina. Retrieved 17 October 2017.
  11. ↑ Anglada-Escudé, Guillem; et al. (2016). "A terrestrial planet candidate in a temperate orbit around Proxima Centauri" (PDF). Nature. 536 (7617): 437–440. arXiv:1609.03449. Bibcode:2016Natur.536..437A. doi:10.1038/nature19106. ISSN 0028-0836. PMID 27558064.
  12. ↑ Feroz, F.; Hobson, M. P. (2014). "Bayesian analysis of radial velocity data of GJ667C with correlated noise: evidence for only two planets". Monthly Notices of the Royal Astronomical Society. 437 (4): 3540–3549. arXiv:1307.6984. Bibcode:2014MNRAS.437.3540F. doi:10.1093/mnras/stt2148.
  13. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 PHL's Exoplanets Catalog – Planetary Habitability Laboratory @ UPR Arecibo
  14. ↑ "Confirmed Planet Overview Page: Kepler-452 b". NASA Exoplanet Archive. NASA Exoplanet Science Institute. Retrieved 4 June 2016.
  15. ↑ "Confirmed Planet Overview Page: Kepler-62f". NASA Exoplanet Archive. NASA Exoplanet Science Institute. Retrieved 4 June 2016.
  16. ↑ N. Astudillo-Defru (March 17, 2017), The HARPS search for southern extra-solar planets (PDF), retrieved March 17, 2017
  17. 1 2 3 4 Delrez, Laetitia; Gillon, Michael; H.M.J, Amaury; Brice-Oliver Demory, Triaud; de Wit, Julien; Ingalls, James; Agol, Eric; Bolmont, Emeline; Burdanov, Artem; Burgasser, Adam J.; Carey, Sean J.; Jehin, Emmanuel; Leconte, Jeremy; Lederer, Susan; Queloz, Didier; Selsis, Franck; Grootel, Valerie Van (9 January 2018). "Early 2017 observations of TRAPPIST-1 with Spitzer". arXiv:1801.02554 [astro-ph.EP].
  18. 1 2 3 4 Grimm, Simon L.; Demory, Brice-Olivier; Gillon, Michael; Dorn, Caroline; Agol, Eric; Burdanov, Artem; Delrez, Laetitia; Sestovic, Marko; Triaud, Amaury H.M.J.; Turbet, Martin; Bolmont, Emeline; Caldas, Anthony; de Wit, Julien; Jehin, Emmanuel; Leconte, Jeremy; Raymond, Sean N.; Van Grootel, Valerie; Burgasser, Adam J.; Carey, Sean; Fabrycky, Daniel; Heng, Kevin; Hernandez, David M.; Ingalls, James G.; Lederer, Susan; Selsis, Franck; Queloz, Didier (5 February 2018). "The nature of the TRAPPIST-1 exoplanets". arXiv:1802.01377 [astro-ph.EP].
  19. ↑ Dickinson, David (19 April 2017). "Welcome to LHS 1140b: A Super-Earth in the Habitable Zone". Sky & Telescope. Retrieved 17 October 2017.
  20. ↑ Torres, Guillermo; Kane, Stephen R.; Rowe, Jason F.; Batalha, Natalie M.; Henze, Christopher E.; Ciardi, David R.; Barclay, Thomas; Borucki, William J.; Buchhave, Lars A. "Validation of Small Kepler Transiting Planet Candidates in or near the Habitable Zone". The Astronomical Journal. 154 (6). arXiv:1711.01267. Bibcode:2017AJ....154..264T. doi:10.3847/1538-3881/aa984b.
  21. ↑ "Confirmed Planet Overview Page: Kepler-296e". NASA Exoplanet Archive. NASA Exoplanet Science Institute. Retrieved 4 June 2016.
  22. ↑ "Confirmed Planet Overview Page: Kepler-62e". NASA Exoplanet Archive. NASA Exoplanet Science Institute. Retrieved 4 June 2016.
  23. ↑ "Confirmed Planet Overview Page: K2-3d". NASA Exoplanet Archive. NASA Exoplanet Science Institute. Retrieved 4 June 2016.
  24. ↑ "Confirmed Planet Overview Page: K2-18 b". NASA Exoplanet Archive. NASA Exoplanet Science Institute. Retrieved 4 June 2016.
  25. ↑ "Confirmed Planet Overview Page: Kepler-61 b". NASA Exoplanet Archive. NASA Exoplanet Science Institute. Retrieved 4 June 2016.
  26. ↑ "Confirmed Planet Overview Page: Kepler-22 b". NASA Exoplanet Archive. NASA Exoplanet Science Institute. Retrieved 4 June 2016.
  27. ↑ "Confirmed Planet Overview Page: K2-9b". NASA Exoplanet Archive. NASA Exoplanet Science Institute. Retrieved 4 June 2016.
  28. ↑ "Confirmed Planet Overview Page: Kepler-296 f". NASA Exoplanet Archive. NASA Exoplanet Science Institute. Retrieved 4 June 2016.
  29. ↑ Wenz, John (15 November 2017). "A potentially habitable planet has been discovered just 11 light-years away". Astronomy. Retrieved 19 November 2017.
  30. ↑ Evidence for at least three planet candidates orbiting HD20794 (PDF), May 16, 2017, pp. 1, 9, retrieved May 19, 2017
  31. ↑ "HADES RV Programme with HARPS-N at TNG: V. A super-Earth on the inner edge of the habitable zone of the nearby M-dwarf GJ 625". A. Suárez Mascareño , J. I. González Hernández , R. Rebolo, S. Velasco, B. Toledo-Padrón, L. Affer , M. Perger, G. Micela, I. Ribas, J. Maldonado , G. Leto , R. Zanmar Sanchez , G. Scandariato , M. Damasso , A. Sozzetti , M. Esposito , E. Covino , A. Maggio , A. F. Lanza , S. Desidera, A. Rosich , A. Bignamini, R. Claudi, S. Benatti, F. Borsa, M. Pedani, E. Molinari, J. C. Morales , E. Herrero , and M. Lafarga (May 18, 2017).
  32. ↑ "Confirmed Planet Overview Page: HD 219134 g". NASA Exoplanet Archive. NASA Exoplanet Science Institute. Retrieved 14 February 2018.
  33. ↑ Kaltenegger, L.; et al. (2011). "A Habitable Planet around HD 85512?". arXiv:1108.3561. Bibcode:2011arXiv1108.3561K.
  34. ↑ Mendez, Abel (1 August 2012). "Five Potential Habitable Exoplanets Now" (Press release). Planetary Habitability Laboratory @ UPR Arecibo. Retrieved 4 June 2015.
  35. ↑ Kopparapu, Ravi Kumar; et al. (2013). "Habitable Zones Around Main-Sequence Stars: New Estimates". The Astrophysical Journal. 765: 131. arXiv:1301.6674. Bibcode:2013ApJ...765..131K. doi:10.1088/0004-637X/765/2/131.
  36. ↑ Mendez, Abel (29 January 2013). "A New Habitable Zone" (Press release). Planetary Habitability Laboratory @ UPR Arecibo. Retrieved 4 June 2015.
  37. ↑ Barclay, Thomas; et al. (2013). "A super-Earth-sized planet orbiting in or near the habitable zone around Sun-like star". The Astrophysical Journal. 768: 101. arXiv:1304.4941. Bibcode:2013ApJ...768..101B. doi:10.1088/0004-637X/768/2/101.
  38. ↑ Kane, Stephen R.; et al. (2013). "A Potential Super-Venus in the Kepler-69 System". The Astrophysical Journal. 770: L20. arXiv:1305.2933. Bibcode:2013ApJ...770L..20K. doi:10.1088/2041-8205/770/2/L20.
  39. ↑ Mendez, Abel (28 December 2012). "Two Nearby Habitable Worlds?" (Press release). Planetary Habitability Laboratory @ UPR Arecibo. Retrieved 4 June 2015.
  40. ↑ "Kepler Candidate Overview Page: KOI-1686.01". NASA Exoplanet Archive. NASA Exoplanet Science Institute. Retrieved 28 December 2015.
  41. ↑ Clavin, Whitney; et al. (6 January 2015). "NASA's Kepler Marks 1,000th Exoplanet Discovery, Uncovers More Small Worlds in Habitable Zones". NASA. Retrieved 6 January 2015.

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