page_title: Gliese 581c
hierarchical_section_title: Gliese 581c
caption_attribution_description: English: Comparison of several possible sizes for the exoplanet Gliese 581 c with the Solar System planets Earth and Neptune, using approximate models of planetary radius as a function of mass[1] for several possible compositions, based on mass reported in the Extrasolar Planets Encyclopaedia[2] as of 2010-10-03. Models include: &#160;&#160; water world with a rocky core, composed of 75% H2O, 3% Fe, 22% MgSiO3 &#160;&#160; hypothetical pure water (ice) planet, the largest size for Gliese 581 c without a significant H/He envelope &#160;&#160; rocky terrestrial "Earth-like" planet, composed of 67% Fe, 32.5% MgSiO3 &#160;&#160; hypothetical pure iron planet, Gliese 581 c's theoretical smallest size Gliese 581 c is not likely to be smaller than the iron planet, and will be considerably larger than the water planet if significant H or He is present. For non-transiting planets, all modeled sizes will be underestimates to the extent that the planet's actual mass is larger than the reported minimum mass. ↑ Seager, S.; M. Kuchner, C. A. Hier-Majumder and B. Militzer (2007). "Mass–radius relationships for solid exoplanets". The Astrophysical Journal 669: 1279–1297. DOI:10.1086/521346. Retrieved on 2010-08-27. ↑ Extrasolar Planets Encyclopaedia (2010-09-30). Retrieved on 2010-10-03.
context_page_description: Gliese 581c is a planet orbiting within the Gliese 581 system. 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.
  Gliese 581c 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 so if life had a chance to emerge, the best hope of survival would be in the "terminator zone".
  In astronomical terms, the Gliese 581 system is relatively close to Earth, at 20.37 light-years 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.
context_section_description: Gliese 581c /ˈɡliːzə/ (Gl 581c or GJ 581c) is a planet orbiting within the Gliese 581 system. 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 with masses greater than Earth's up to 10 Earth masses).
  Gliese 581c 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 presents the same face to its primary) so if life had a chance to emerge, the best hope of survival would be in the "terminator 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.
caption: Size comparison of Gliese 581c with Earth and Neptune.
  
  (Based on selected hypothetical modeled compositions)
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