page_title: Gliese 667
section_title: Planetary system
hierarchical_section_title: Gliese 667 / Gliese 667 C / Planetary system
caption_attribution_description: English: The 6-Earth-mass exoplanet Gliese 667Cb orbits its low-mass host star at a distance equal to only 1/20th of the Earth–Sun distance. The host star Gliese 667C is a companion to two other low-mass stars, which are seen here in the distance.
context_page_description: Gliese 667 is a triple-star system in the constellation Scorpius lying at a distance of about 6.8 pc from Earth. All three of the stars have masses smaller than the Sun. There is a 12th magnitude star close to the other three, but it is not gravitationally bound to the system. To the naked eye, the system appears to be a single faint star of magnitude 5.89.
  The system has a relatively high proper motion, exceeding 1 second of arc per year.
  The two brightest stars in this system, GJ 667 A and GJ 667 B, are orbiting each other at an average angular separation of 1.81 arcseconds with a high eccentricity of 0.58. At the estimated distance of this system, this is equivalent to a physical separation of about 12.6 AU, or nearly 13 times the separation of the Earth from the Sun. Their eccentric orbit brings the pair as close as about 5 AU to each other, or as distant as 20 AU, corresponding to an eccentricity of 0.6. This orbit takes approximately 42.15 years to complete and the orbital plane is inclined at an angle of 128° to the line of sight from the Earth.
context_section_description: Two extrasolar planets, Gliese 667 Cb (GJ 667 Cb) and Cc, have been confirmed orbiting Gliese 667 C by radial velocity measurements of GJ 667.  Up to five additional planets have been claimed, however these have not been confirmed and may be artifacts caused by correlated noise in the data.
  Planet Cb was first announced by the European Southern Observatory's HARPS group on 19 October 2009. The announcement was made together with 29 other planets, while Cc was first mentioned by the same group in a pre-print made public on 21 November 2011. Announcement of a refereed journal report came on 2 February 2012 by researchers at the University of Göttingen/Carnegie Institution for Science. In this announcement, GJ 667 Cc was described as one of the best candidates yet found to harbor liquid water, and thus, potentially, support life on its surface. A detailed orbital analysis and refined orbital parameters for Gliese 667 Cc were presented. Based on GJ 667 C's bolometric luminosity, GJ 667 Cc would receive 90% of the light Earth does, however much of that electromagnetic radiation would be in the invisible infrared light part of the spectrum. Based on black body temperature calculation, GJ 667 Cc should absorb more overall electromagnetic radiation, making it warmer (277.4 K) and placing it slightly closer to the "hot" edge of the habitable zone than Earth (254.3 K).
  From the surface of Gliese 667 Cc, the second confirmed planet out that orbits along the middle of the habitable zone, Gliese 667 C would have an angular diameter of 1.24 degrees--2.3 times larger than our Sun appears from the surface of the Earth, covering 5.4 times more area--but would still only occupy 0.003 percent of Gliese 667 Cc's sky sphere or 0.006 percent of the visible sky when directly overhead.
  Five additional planets may exist in the system, with three of them, Cf, Ce, and Cg, thought to be relatively certain to exist. However, subsequent studies showed that the other planets in the system could possibly be artifacts of noise and stellar activity, cutting the minimum number of planets down to two. Cf and Ce, the fifth and fourth discovered respectively, have the highest chances to exist, although they are still controversial. Cd and Ch are least likely to exist, the former of which being a signal related to stellar activity.
caption: Artist's impression of Gliese 667 Cb with the Gliese 667 A/B binary in the background
exif: {"Image ImageDescription": "On 19 October 2009, the team who built the High Accuracy Radial Velocity Planet Searcher, better known as HARPS, the spectrograph for ESO\u2019s 3.6-metre telescope, reported on the incredible discovery of some 32 new exoplanets, cementing HARPS\u2019s position as the world\u2019s foremost exoplanet hunter. One of these is surrounding the star Gliese 667 C, which belongs to a triple system. The 6 Earth-mass exoplanet circulates around its low-mass host star at a distance equal to only 1/20th of the Earth-Sun distance. The host star is a companion to two other low-mass stars, which are seen here in the distance."}