List of potential habitable exoplanets

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.

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

Methodology

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.

List

The data is from the Habitable Exoplanets Catalog. 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.

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.

Rank	Name	ESI	SPH	HZD	HZC	HZA	pClass	hClass	Distance (ly)	Status	Year of discovery
0N/A	!Earth	1 !1.00	0.72	-0.50	-0.31	-0.52	warm terran	mesoplanet	0	non-exoplanet
70001000000000000001	KOI-1686.01	0.89 !0.89	1.00	-0.58	-0.13	-0.14	warm superterran	mesoplanet	1033.8	Kepler candidate	2012
70002000000000000002	KOI-3010.01	0.87 !0.87	0.14	-0.79	-0.08	-0.12	warm superterran	mesoplanet	1218.0	Kepler candidate	2012
70003000000000000003	KOI-701.03	0.85 !0.85	0.72	-0.61	+0.02	+0.02	warm superterran	mesoplanet	741.7	Kepler candidate	2011
70004000000000000004	KOI-463.01	0.83 !0.83	0.00	-0.89	+0.01	-0.05	warm superterran	thermoplanet	564.3	Kepler candidate	2011
70005000000000000005	Kepler-62e	0.82 !0.82	0.28	-0.71	+0.08	+0.05	warm superterran	mesoplanet	1200.0	Confirmed	2013
70006000000000000006	Gliese 581 g	0.82 !0.82	0.47	-0.41	-0.07	-0.01	warm superterran	mesoplanet	20.2	Unconfirmed	2010
70007000000000000007	Gliese 667C c	0.79 !0.79	0.98	-0.56	+0.28	+0.24	warm superterran	mesoplanet	23.6	Confirmed	2011
70008000000000000008	Kepler-69c	0.79 !0.79	0.00	-0.86	+0.02	-0.07	warm superterran	thermoplanet	1683.6	Kepler candidate	2013
70009000000000000009	KOI-812.03	0.79 !0.79	0.05	-0.81	+0.23	+0.16	warm superterran	mesoplanet	1474.1	Kepler candidate	2011
700110000000000000010	KOI-2474.01	0.78 !0.78	0.00	-0.89	+0.12	+0.02	warm superterran	thermoplanet	1605.7	Kepler candidate	2012
700111000000000000011	KOI-2418.01	0.77 !0.77	0.39	-0.29	+0.12	+0.21	warm superterran	mesoplanet	996.9	Kepler candidate	2012
700112000000000000012	KOI-2469.01	0.76 !0.76	0.11	-0.72	+0.42	+0.30	warm superterran	mesoplanet	1556.8	Kepler candidate	2012
700113000000000000013	Kepler-61 b	0.76 !0.76	0.39	-0.72	+0.45	+0.33	warm superterran	mesoplanet	917.1	Confirmed	2013
700114000000000000014	Kepler-22 b	0.75 !0.75	0.87	-0.47	+0.50	+0.40	warm superterran	mesoplanet	535.9	Confirmed	2011
700115000000000000015	KOI-1298.02	0.75 !0.75	0.95	-0.56	+0.49	+0.40	warm superterran	mesoplanet	1496.7	Kepler candidate	2011
700116000000000000016	Tau Ceti e	0.74 !0.74	0.00	-0.91	+0.29	+0.15	warm superterran	thermoplanet	11.9	Unconfirmed	2012
700117000000000000017	KOI-854.01	0.74 !0.74	0.44	-0.33	+0.26	+0.33	warm superterran	mesoplanet	1077.7	Kepler candidate	2011
700118000000000000018	KOI-2762.01	0.73 !0.73	0.50	-0.25	+0.35	+0.39	warm superterran	mesoplanet	1169.5	Kepler candidate	2012
700119000000000000019	KOI-2834.01	0.73 !0.73	0.55	-0.62	+0.65	+0.45	warm superterran	mesoplanet	2150.0	Kepler candidate	2012
700120000000000000020	KOI-1871.01	0.72 !0.72	0.00	-0.81	+0.61	+0.37	warm superterran	mesoplanet	1176.7	Kepler candidate	2012
700121000000000000021	Kepler-62f	0.69 !0.69	0.00	+0.36	-0.07	+0.11	warm superterran	psychroplanet	1200.0	Confirmed	2013
700122000000000000022	Gliese 163 c	0.68 !0.68	0.00	-0.97	+0.8	+0.42	warm superterran	thermoplanet	48.9	Confirmed	2012
700123000000000000023	HD 40307 g	0.67 !0.67	0.29	-0.07	+0.78	+0.63	warm superterran	mesoplanet	41.7	Unconfirmed	2012
700124000000000000024	KOI-2770.01	0.58 !0.58	0.00	+0.42	+0.58	+0.70	warm superterran	psychroplanet	1470.3	Kepler candidate	2012
700125000000000000025	KOI-518.03	0.56 !0.56	0.00	+0.57	+0.62	+0.75	warm superterran	psychroplanet	878.3	Kepler candidate	2011
700126000000000000026	Gliese 581 d	0.5 !0.50	0.00	+0.68	+0.58	+0.82	warm superterran	psychroplanet	20.2	Confirmed	2007
@1N/A	~Mars	0.64 !0.64	0.00	+0.33	-0.13	-1.12	warm subterran	psychroplanet	0	non-exoplanet
@2N/A	~Mercury	0.39 !0.39	0.00	-1.46	-0.52	-1.37	hot mercurian	non-habitable	0	non-exoplanet
@3N/A	~Venus	0.78 !0.78	0.00	-0.93	-0.28	-0.70	warm terran	thermoplanet	0	non-exoplanet

References

 2. http://www.hpcf.upr.edu/~abel/phl/phl_hec_all_unconfirmed.csv.zip

 3. http://www.hpcf.upr.edu/~abel/phl/phl_hec_all_confirmed.csv.zip

See also

• Earth analog
• Habitable zone
• List of nearest terrestrial exoplanet candidates
• Planetary habitability
• Super-Earth

External links

• "The Habitable Exoplanets Catalog" (PHL/UPR Arecibo)
• Habitable Exoplanets Catalogue ranks alien worlds on suitability for life