Gliese 581 c is an extrasolar planet found orbiting the red dwarf Gliese 581. It is a Super-Earth (a category of planets from 5 to 10 Earth masses) with about 5.5 times the mass of our home planet. Gliese 581 c was discovered in April of 2007 along with its sibling planets Gliese 581 b and Gliese 581 d. It was originally thought to be an Earth-like world, but later analysis showed that Gliese 581 c is orbiting slightly closer to its star than the habitable zone's inner boundary and therefore may be a Venus analogue. Also, it is tidally locked (always faces the parent star with the same face) so if life had a chance to emerge, the best hope of survival would be in "the Terminator zone."
The Gliese 581 system is relatively close to Earth, at 20.37 light-years(192 trillion km or 119 trillion miles) in the direction of the constellation of Libra
Gliese 581 c has a mass around 5.5 times the mass of Earth. However, since it was discovered by Doppler Spectroscopy, the radius of 581 c is not known.