Gliese 581 g extrasolar planet, artwork. This planet orbits the Gliese 581 star, around 20 light years from Earth in the constellation of Libra. The parent star and three inner planets are at upper left. Gliese 581 g takes 37 Earth days to orbit the star at a distance of around 22 million kilometres. It is in the star's habitable zone, and is of a similar size to Earth. This makes it one of the best candidates for alien life (a 'Goldilocks planet') among over 490 exoplanets discovered to date. The discovery, part of the Lick-Carnegie Exoplanet Survey, was announced in September 2010.