Gliese 581g （格利澤581g） PHI: 0.45

Gliese 581 g, also Gl 581 g or GJ 581 g, is an extrasolar planet, orbiting the red dwarf star Gliese 581, 20.5 light-years from Earth in the constellation of Libra. It is the sixth planet discovered in the Gliese 581 planetary system and the fourth in order of increasing distance from the star. The discovery was announced by the Lick-Carnegie Exoplanet Survey in late September 2010, after a decade of observation. (From Wikipedia)

Studies indicate the planet is situated near the middle of the habitable zone of its parent star, where temperatures are neither too hot nor too cold to sustain Earth-like life (it is expected to be around 20 Farenheit degrees cooler than Earth, however). If it is a rocky planet, favorable atmospheric conditions could permit the presence of liquid water, a necessity for all known life, on its surface. With a mass 3.1 to 4.3 times Earth's, Gliese 581 g is considered a super-Earth and is the planet closest in size to Earth known in a habitable zone. This makes it the most Earth-like Goldilocks planet found outside the Solar System and the exoplanet with the greatest recognized potential for harboring life. (From Wikipedia)

The detection of Gliese 581 g after such a short period of searching and at such close proximity has led some astronomers to hypothesize that the proportion of stars with habitable planets may be greater than ten percent. (From Wikipedia)