Gliese 581 d /ˈɡliːzə/ (often shortened to Gl 581 d or GJ 581 d) is a possible extrasolar planet orbiting the star Gliese 581 approximately 20.4 light-years away in the constellation of Libra. It is the third planet claimed in the system and (assuming a six-planet model) the fifth in order from the star. Though not confirmed to be a terrestrial planet and significantly more massive than Earth (at 6.98 Earth masses), the Super-Earth is the first exoplanet of terrestrial mass proposed to orbit within the habitable zone of its parent star.