C: First Earth-like Planet Found in Habitable Zone

Planetary system Gliese 581 (Artist's impression)

Astronomy 1 – Introduction to Astronomy (Spring 2007)

C:  First Earth-like Planet Found in Habitable Zone

[ Students and professors, please read. ]

Press release date:  April 25, 2007

Source:  ESO’s press release: http://www.eso.org/outreach/press-rel/pr-2007/pr-22-07.html

Summary:  Located in the constellation Libra (“the Scales”) at a distance of 20.5 light-years from Earth, the exoplanet, Gliese 581 c, “c” for short, was discovered orbiting the red dwarf star, Gliese 581, by a team* of Swiss, French and Portuguese scientists using the European Southern Observatory’s (ESO) telescope in La Silla, Chile, along with an ultra-precise spectrograh called HARPS.  The planet is 14 times closer to the star it orbits than the Earth is to the Sun, but because red dwarf stars are low-energy, the research team believes with celebration that the average temperature of the planet is somewhere between 30 and 100 degrees Fahrenheit – the right temperature for liquid water.  This planet’s minimum mass is five times larger than Earth’s mass, with a diameter of possibly 50% larger, meaning gravity at the surface that is twice as strong.  It should either be rocky or covered with oceans.  It should have an atmosphere, but what’s in it is still a mystery.  The author of this report thinks they should enlist the aid of Travis Barman, astronomer at the Lowell Observatory in Arizona, who detected water in the atmosphere of HD209458b (space.com).

Significance:  Of 220 planets found near Earth, Gliese 581 c is the only one found outside our solar system that meets scientists’ standards for habitability, which include a size relatively similar to Earth’s with temperatures that would permit liquid water; all others suffering the “Goldilocks” syndrome:  too hot, too cold, too big and gaseous, etcetera.  As such, it is a big step in the search for extra-terrestrial life and will probably become a target for future space missions.  About 80 percent of the stars near Earth are red dwarfs like Gliese 581, and this discovery of an Earth-like exoplanet circling a red dwarf will fuel studies of planets circling similar dim stars.

*The team is composed of Stéphane Udry, Michel Mayor, Christophe Lovis, Francesco Pepe, and Didier Queloz (Geneva Observatory, Switzerland), Xavier Bonfils (Lisbonne Observatory, Portugal), Xavier Delfosse, Thierry Forveille, and C.Perrier (LAOG, Grenoble, France), François Bouchy (Institut d’Astrophysique de Paris, France), and Jean-Luc Bertaux (Service d’Aéronomie du CNRS, France).

Additional sources used for this report:



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