Last Update: December 15, 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.
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 by this standard (ESI > 0.90). Planets with high ESI values are not necessarily more habitable as habitability depends of other unknown factors such as surface and atmospheric composition. Earth, Mars, Jupiter, and Neptune are shown for scale on the right.
These are all known potentially habitable exoplanets divided on four categories based on their location in the habitable zone (HZ) and size (conservative or optimistic). Planets in the Conservative HZ category are more likely to support surface liquid water. Planets in the Optimistic-Size category are less likely to be rocky worlds. Image Credit: PHL @ UPR Arecibo.
These are orbital analyses for all the planets in 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.
These are simple orbital visualizations of the stellar systems of the planets in the catalog. They include to scale all planets in each stellar system including those hot (red), cold (blue), and potentially habitable (green). Stars and planets are not to scale with each other (size estimated when not known). Each thumbnail links to the stellar diagram. The habitable zone (shaded green area) corresponds to the optimistic case for super-Earths (~5 Earth masses).
Distribution by Stellar Flux and Distance from Earth
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.
Location in the night sky of all the known stellar systems with potentially habitable worlds (some systems have more than one planet). Click the image to enlarge. Image Credit: PHL @ UPR Arecibo, Jim Cornmell.