List of potential habitable exoplanets

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Artist's impression of Kepler-22b, a "Super-Earth" within its star's habitable zone.
Artist's impression of Gliese 581 d, which is one of a few potential habitable exoplanets confirmed so far

This is a list of potential habitable exoplanets candidates ranked by similarity with Earth using the Earth Similarity Index. The list is based on methodology and estimations provided by the Habitable Exoplanets Catalog, which is maintained by the Planetary Habitability Laboratory at UPR-Arecibo.

Habitable zone[edit]

Main article: Habitable zone

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.[1][2]

A potentially habitable planet implies a terrestrial planet within the CHZ and with conditions roughly comparable to those of Earth (i.e. an Earth analog) and thus potentially favourable to life.

Although only about a dozen[citation needed] planets have been confirmed in the habitable zone, the Kepler spacecraft has identified a further 54 candidates[citation needed] and current estimates indicate that there are "at least 500 million" planets in habitable zones in the Milky Way.[3]

On 4 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,[4][5] 11 billion of which may be orbiting Sun-like stars.[6] The nearest such planet could be 12 light-years away, according to the scientists.[4][5]

List from the Habitable Exoplanets Catalog[edit]

The data is from the Habitable Exoplanets Catalog.[7] This habitability index does not take into account the differences in the habitability of certain types of stars and star systems, such as red dwarfs and binary star systems. See habitability of red dwarf systems for more information.

Key[edit]

The planets listed below are evaluated on seven different criteria:

  • Earth Similarity Index (ESI) — Similarity to Earth on a scale from 0 to 1, with 1 being the most Earth-like. ESI depends on the planet's radius, density, escape velocity, and surface temperature.
  • Standard Primary Habitability (SPH) — Suitability for vegetation on a scale from 0 to 1, with 1 being best-suited for growth. SPH depends on surface temperature (and relative humidity if known).
  • Habitable Zone Distance (HZD) — Distance from the center of the star's habitable zone, scaled so that –1 represents the inner edge of the zone, and +1 represents the outer edge. HZD depends on the star's luminosity and temperature and the size of the planet's orbit.
  • Habitable Zone Composition (HZC) — Measure of bulk composition, where values close to zero are likely iron–rock–water mixtures. Values below –1 represent bodies likely composed mainly of iron, and values greater than +1 represent bodies likely composed mainly of gas. HZC depends on the planet's mass and radius.
  • Habitable Zone Atmosphere (HZA) — Potential for the planet to hold a habitable atmosphere, where values below –1 represent bodies likely with little or no atmosphere, and values above +1 represent bodies likely with thick hydrogen atmospheres (e.g. gas giants). Values between –1 and +1 are more likely to have atmospheres suitable for life, though zero is not necessarily ideal. HZA depends on the planet's mass, radius, orbit size, and the star's luminosity.
  • Planetary Class (pClass) — Classifies objects based on thermal zone (hot, warm, or cold, where warm is in the habitable zone) and mass (asteroidan, mercurian, subterran, terran, superterran, neptunian, and jovian).
  • Habitable Class (hClass) — Classifies habitable planets based on temperature: hypopsychroplanets (hP) = very cold (< −50 °C); psychroplanets (P) = cold; mesoplanets (M) = medium-temperature (0–50 °C; not to be confused with the other definition of mesoplanets); thermoplanets (T) = hot; hyperthermoplanets (hT) = very hot (> 100 °C). Mesoplanets would be ideal for complex life, whereas class hP or hT would only support extremophilic life. Non-habitable planets are simply given the class NH.

Table[edit]

For comparison purposes, four solar terrestrial planets are included in the list. Most of the confirmed exoplanets in the data still rank very low as compared to the NASA Kepler candidates (KOI).

Name ESI SPH HZD HZC HZA pClass hClass Distance (ly) Status Year of
discovery
0N/A !Earth 1.00 0.72 -0.50 -0.31 -0.52 warm terran mesoplanet 0 non-exoplanet prehistoric
1 KOI-3284.01 0.90 0.80 -0.90 +0.34 -0.64 warm terran mesoplanet 472.5 Kepler candidate 2011
2 KOI-1686.01 0.89 0.47 -0.60 -0.13 -0.14 warm superterran mesoplanet 1033.8 Kepler candidate 2011
3 KOI-3010.01 0.87 0.95 -0.80 -0.08 -0.12 warm superterran mesoplanet 1218.0 Kepler candidate 2011
4 Gliese 667 Cc 0.84 0.59 -0.64 +0.11 +0.14 warm superterran mesoplanet 23.6 Confirmed 2011
5 KOI-4742.01 0.83 1.00 -0.72 0.08 0.05 warm superterran mesoplanet 1291.6 Kepler candidate 2011
6 Kepler-62e 0.83 0.99 -0.71 +0.08 +0.05 warm superterran mesoplanet 1199.7 Confirmed 2013
7 KOI-1422.04 0.82 0.33 -0.54 0.08 0.12 warm superterran mesoplanet 1089.6 Kepler candidate 2011
8 Gliese 832 c[8] 0.81 1 -1 0 0 warm superterran mesoplanet 16.1 Confirmed 2014
9 KOI-142.02 0.80 0.01 -0.16 0.00 0.08 warm superterran psychroplanet 1015.5 Kepler candidate 2011
10 KOI-2529.02 0.79 0.52 -0.86 +0.19 +0.11 warm superterran mesoplanet 1339.4 Kepler candidate 2011
11 KOI-2474.01 0.78 0.00 -0.89 +0.12 +0.02 warm superterran mesoplanet 1605.7 Kepler candidate 2011
12 KOI-2418.01 0.77 0.01 -0.33 +0.12 +0.21 warm superterran psychroplanet 996.9 Kepler candidate 2011
13 Kepler-69c 0.77 0.01 -0.87 0.16 0.05 warm superterran mesoplanet 1683.6 Confirmed 2011
14 Tau Ceti e 0.77 0.00 -0.91 +0.29 +0.15 warm superterran mesoplanet 11.9 Unconfirmed 2012
15 Gliese 581 g 0.89 1.00 -0.26 0.02 -0.14 warm superterran mesoplanet 20.2 dubious 2010
16 KOI-4550.01 0.76 1.00 -0.68 +0.45 +0.34 warm superterran mesoplanet 1847.5 Kepler candidate 2011
17 KOI-2469.01 0.76 0.93 -0.73 +0.42 +0.30 warm superterran mesoplanet 1556.8 Kepler candidate 2011
18 KOI-4333.01 0.76 0.00 -0.90 +0.15 +0.03 warm superterran thermoplanet 2504.7 Kepler candidate 2011
19 Gliese 667 Cf 0.76 0.00 -0.26 +0.01 +0.13 warm superterran psychroplanet 23.6 dubious 2013
20 KOI-1298.02 0.75 0.69 -0.58 +0.49 +0.40 warm superterran mesoplanet 1496.8 Kepler candidate 2011
21 KOI-2992.01 0.75 0.35 -0.50 +0.41 +0.38 warm superterran mesoplanet 1375.4 Kepler candidate 2011
22 KOI-854.01 0.74 0.94 -0.69 +0.58 +0.42 warm superterran mesoplanet 1077.7 Kepler candidate 2011
23 HD 40307 g 0.74 1.00 -0.31 +0.78 +0.61 warm superterran mesoplanet 41.7 Confirmed 2012
24 KOI-4036.01 0.73 0.99 -0.65 +0.66 +0.45 warm superterran mesoplanet 1135.0 Kepler candidate 2011
25 Kepler-61b 0.73 0.69 -0.89 +0.55 +0.33 warm superterran mesoplanet 1062.8 Confirmed 2013
26 KOI-4745.01 0.73 0.63 -0.51 +0.57 +0.45 warm superterran mesoplanet 2564.4 Kepler candidate 2011
27 Gliese 163 c 0.73 0.08 -0.95 +0.81 +0.43 warm superterran mesoplanet 48.9 Confirmed 2012
28 KOI-2762.01 0.73 0.02 -0.29 +0.35 +0.39 warm superterran psychroplanet 1169.5 Kepler candidate 2011
29 KOI-1871.01 0.72 0.57 -0.82 +0.61 +0.37 warm superterran mesoplanet 1176.7 Kepler candidate 2011
30 Kepler-22b 0.71 0.95 -0.66 +0.74 +0.47 warm superterran mesoplanet 619.4 Confirmed 2011
31 KOI-3282.01 0.71 0.35 -0.89 +0.63 +0.37 warm superterran mesoplanet 1162.9 Kepler candidate 2011
32 KOI-4450.01 0.71 0.12 -0.83 +0.60 +0.34 warm superterran mesoplanet 2553.4 Kepler candidate 2011
33 KOI-4054.01 0.71 0.07 -0.86 +0.60 +0.34 warm superterran mesoplanet 1770.4 Kepler candidate 2011
34 KOI-4005.01 0.70 0.00 -0.92 +0.58 +0.30 warm superterran thermoplanet 1914.8 Kepler candidate 2011
35 KOI-4583.01 0.67 0.01 -0.11 +0.79 +0.64 warm superterran psychroplanet 3265.0 Kepler candidate 2011
36 Kepler-62f 0.67 0.00 +0.36 -0.07 +0.11 warm superterran psychroplanet 1199.7 Confirmed 2013
37 KOI-4087.01 0.65 0.00 +0.19 +0.05 +0.27 warm superterran psychroplanet 706.5 Kepler candidate 2011
38 Gliese 667 Ce 0.60 0.00 +0.43 +0.01 +0.28 warm superterran psychroplanet 23.6 dubious 2013
39 KOI-2770.01 0.58 0.00 +0.34 +0.58 +0.70 warm superterran psychroplanet 1470.4 Kepler candidate 2011
40 Kepler-186f 0.57 0.01 +0.78 -0.30 -0.26 warm terran hypopsychroplanet 492 Confirmed 2014
41 KOI-518.03 0.56 0.00 +0.47 +0.62 +0.75 warm superterran psychroplanet 878.3 Kepler candidate 2011
42 KOI-4356.01 0.55 0.00 +0.67 +0.31 +0.60 warm superterran psychroplanet 1239.7 Kepler candidate 2011
43 Gliese 581 d 0.53 0.00 +0.65 +0.45 +0.73 warm superterran hypopsychroplanet 20.2 Confirmed 2007
@1N/A ~Venus 0.78 0.00 -0.93 -0.28 -0.70 warm terran hyperthermoplanet 0 non-exoplanet prehistoric
@2N/A ~Mars 0.64 0.00 +0.33 -0.13 -1.12 warm subterran hypopsychroplanet 0 non-exoplanet prehistoric
@3N/A ~Mercury 0.39 0.00 -1.46 -0.52 -1.37 hot mercurian non-habitable 0 non-exoplanet prehistoric

Other habitable planet candidates[edit]

On February 18, 2014, researchers from the University of Hertfordshire announced the discovery of three super-Earths in the habitable zones of relatively nearby red dwarf: GJ 180 c, GJ 422 b, and GJ 682 b.[9]

Other potentially habitable exoplanet candidates include:

Key
Planet name Distance from Earth [ly] Mass [M] Radius [R] Discovery date Notes Ref.
HD 85512 b 36 3.60 2.50 2011-08-17 [10]
GJ 1214 b 42 6.55 2.68 2009-12-16 [11]


See also[edit]

References[edit]

  1. ^ "VPL Glossary". washington.edu. 
  2. ^ "The Goldilocks Zone". NASA. 2 October 2003. 
  3. ^ Borenstein, Seth (19 February 2011). "Cosmic census finds crowd of planets in our galaxy". Associated Press. 
  4. ^ a b Overbye, Dennis (November 4, 2013). "Far-Off Planets Like the Earth Dot the Galaxy". New York Times. Retrieved November 5, 2013. 
  5. ^ a b Petigura, Eric A.; Howard, Andrew W.; Marcy, Geoffrey W. (October 31, 2013). "Prevalence of Earth-size planets orbiting Sun-like stars". Proceedings of the National Academy of Sciences of the United States of America. arXiv:1311.6806. Bibcode:2013PNAS..11019273P. doi:10.1073/pnas.1319909110. Retrieved November 5, 2013. 
  6. ^ Khan, Amina (November 4, 2013). "Milky Way may host billions of Earth-size planets". Los Angeles Times. Retrieved November 5, 2013. 
  7. ^ PHL's Exoplanets Catalog - Planetary Habitability Laboratory @ UPR Arecibo
  8. ^ [1]
  9. ^ http://star.herts.ac.uk/~hraj/mdwarfs/mds_v4.pdf
  10. ^ Kaltenegger, L.; Udry, S.; Pepe, F. (2011). A Habitable Planet around HD 85512?. arXiv:1108.3561. Bibcode:2011arXiv1108.3561K. 
  11. ^ Rogers, L.A.; Seager, S. (2009-12-16). "Three Possible Origins for the Gas Layer on GJ 1214b". The Astrophysical Journal (abstract) 716 (2): 1208. arXiv:0912.3243. Bibcode:2010ApJ...716.1208R. doi:10.1088/0004-637X/716/2/1208. 

External links[edit]