Gliese 667C c is a potentially habitable planet orbiting one of three stars in a nearby triple-star system. This triple-star system consists of a pair of K-dwarf stars orbiting each other and a fainter red dwarf star orbiting further out, around both the K-dwarf stars. The outer red dwarf star is the star around which Gliese 667C c orbits, and this star is 31 percent as massive and 1.4 percent as luminous as the Sun. Gliese 667C c orbits its host star with a period of 28 days and at a distance that is about 8 times closer than the Earth is from the Sun. Since Gliese 667C c orbits around a faint red dwarf star, the planet receives the same intensity of stellar radiation as the Earth receives from the Sun even though it orbits much closer to its hosts star.
Credit: PHL @ UPR Arecibo/ESO/S. Brunier
The distance of Gliese 667C c from its host star places the planet comfortably within the star’s liquid water habitable zone. This means that temperatures on the surface of Gliese 667C c are expected to be just right to sustain liquid water on the planet’s surface. However, the actual habitability of GJ 667Cc will depend on additional physical parameters such as atmospheric composition, cloud cover and interior dynamics, which are currently unknown. Gliese 667C c is estimated to be at least 4.5 times as massive as the Earth.
As of February 2012, the Planetary Habitability Laboratory at UPR Arecibo regards Gliese 667C c as the fourth potentially habitable planet discovered so far. The other three potentially habitable planets are HD85512 b, Gliese 581 d and Kepler-22 b. The Gliese 667 triple-star system is located at a distance of about 22 light years away towards the constellation of Scorpius. To the unaided eye, this triple-star system appears as a single star with an apparent magnitude of 5.9.
Credit: PHL @ UPR Arecibo
The discovery of Gliese 667C c was first mentioned in a pre-print made public on 21 November 2011 by Xavier Bonfils, et al. entitled “The HARPS search for southern extra-solar planets XXXI. The M-dwarf sample”. A more recent paper with additional observations of Gliese 667C c was published on 2 February 2012 by Guillem Anglada-Escude, et al. entitled “A planetary system around the nearby M dwarf GJ 667C with at least one super-Earth in its habitable zone”.