Gliese 581 c

Gliese 581 c /ˈɡliːzə/ or Gl 581 c is a planet orbiting the red dwarf Gliese 581. It is the second planet discovered in the system and the third in order from the star. With a mass at least 5.5 times that of the Earth, it is classified as a super-Earth (a category of planets from 5 to 10 Earth masses).

Gliese 581 c gained interest from astronomers because it was reported to be the first potentially Earth-like planet in the habitable zone of its star, with a temperature right for liquid water on its surface, and by extension, potentially capable of supporting extremophile forms of Earth-like life. However, further research casts doubt upon the planet's habitability. 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 "the twilight zone."

In astronomical terms, 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. This distance, along with the declination and right ascension coordinates, give its exact location in our galaxy.