Last Update: July 7, 2014
The Habitable Exoplanets Catalog (HEC) list a selection of all known exoplanets with any potential to support life, including some unconfirmed planets. The catalog tries to be as open as possible as not to exclude any object of interest. The selection can be narrowed down as desired using more conservative criteria based on different habitability metrics. The Data section has more technical details. Check the Methods section for an explanation of the metrics and classifications used here.
Potentially Habitable Exoplanets Ranked by the Earth Similarity Index (ESI)
These are artistic representations of all the potentially habitable exoplanets ranked from best to worst by the Earth Similarity Index (ESI), a measure of Earth-likeness based on stellar flux and planet size. None yet seems to be a true Earth-like planet (ESI > 0.90). Not all planets with high ESI values are necessarily more habitable as habitability depends of other unknown factors such as atmospheric composition. Earth, Mars, Jupiter, and Neptune are shown for scale on the right.
Above is a selection of planets that match the Conservative Definition of a Potentially Habitable Exoplanet. These planets are more likely to be of rocky composition and with the right temperatures for liquid water. Image Credit: PHL @ UPR Arecibo.
Above is a selection of planets that match the Optimistic Definition of a Potentially Habitable Exoplanet. These planets are less likely to be of rocky composition or with the right temperatures for liquid water. Image Credit: PHL @ UPR Arecibo.
These are orbital analyses for all the planets of the catalog. It includes the dimensions of the habitable zone and better estimates of the equilibrium temperature for those planets in elliptical orbits. Each thumbnail links to the orbital diagram. Explanations and orbits for all known exoplanets are available in the PHL's Exoplanet Orbital Catalog.
This figure shows all exoplanets that receives up to two times the stellar energy that Earth receives from the Sun (vertical axis). Planets too cold for life are blue and those too hot are red. Planets in the warm zone (i.e. habitable zone) are shown in green with those potentially habitable (i.e. < 2.5 Earth radii) in a darker shade of green (see legend top right). The figure shows how far are these planets from Earth (horizontal axis). The size of the circles approximately corresponds to the relative size of the planets (estimated when not known). A similar version of this plot for all planets is available here.