Five potential habitable exoplanets now
July 25, 2012
Artistic representation of all the five known potential habitable worlds, now including Gliese 581g, the best candidate for an Earth-like exoplanet so far. All of these planets are superterrans (aka Super-Earths) with masses estimated between two and ten Earth masses. Numbers below the planet names correspond to their similarity with Earth as measured in a scale from zero to one with the Earth Similarity Index, one being identical to Earth. (Credit: Planetary Habitability Laboratory)
New data suggests the exoplanet Gliese 581g is the best candidate so far of a potential habitable exoplanet. The nearby star Gliese 581 — located about 20 light years away from Earth in the constellation Libra — has four planets; the outermost planet, Gliese 581d, was already suspected habitable.
This will be the first evidence for any two potential habitable exoplanets that are orbiting the same star.
Based on the new data, Gliese 581g probably has a radius not larger than 1.5 times Earth radii. It receives about the same light flux as Earth does from the Sun due to its closer orbital position around a dim red dwarf star. These factors combine to make Gliese 581g the most Earth-like planet known with an Earth Similarity Index, a measure of Earth-likeness from zero to one, of 0.92 and higher than the previously top candidate Gliese 667Cc, discovered last year.