Extrasolar planet Gliese 581c. Computer artwork of the giant terrestrial planet Gliese 581c, in orbit around the red dwarf star Gliese 581 (not seen). This view is from the surface of one of its moons. Two other moons are seen at lower left and upper right. The parent red dwarf star is below the horizon, so it is night time on this moon, but its landscape is faintly illuminated by reflected sunlight from the planet in the sky. Gliese 581c is the most Earth-like alien planet yet discovered. The Gliese 581 star lies about 20.5 light years from Earth in the constellation Libra.