February 5th, 2012 by Michael Ricciardi
It’s called GJ 667Cc and it’s just 22 light years from Earth — virtually a next door neighbor in our little corner of the galaxy. Most compelling to astronomers is that the planet is smack dab in the middle of its parent star’s habitable zone, the circumstellar region within which liquid water can be sustained on a planet’s surface.
“This planet is the new best candidate to support liquid water and, perhaps, life as we know it,” said the study’s lead scientist, Guillem Anglada-Escudé of the Carnegie Institution for Science, in a press statement.
Some are already calling it the Holy Grail of exoplanetary research.
A star’s habitable zone is determined by its size and magnitude. GJ 667Cc lies within this “just right” region (also known as the “Goldilocks zone”) making its surface neither too hot (which would boil away any surface water) or too cold (which would freeze it);
Located (from an Earth perspective) in the constellation Scorpius, GJ 667Cc takes just 28 days to orbit its parent star, a red dwarf, and is estimated to be 4.5 times the mass of our Earth. This makes the planet a super Earth which would mean a stronger gravitational “pull” than found here (you would weigh 4.5 times more) and also probably a denser atmosphere. A ‘super Earth’ is any planet larger than the Earth but substantially smaller than the ‘gas giants’ of our solar system, such as Jupiter and Saturn.
It is the second planet discovered orbiting this star — that being GJ 667Cb, discovered in 2009 (note: the ‘G’ in the name stands for Gliese [glee’ zuh], a star system with many recently discovered exoplanets).
The M-class dwarf star (GJ 667C) is just 38% of the mass of our sun and is part of a triple star system. To the naked eye, the star appears to be single faint star with only .3% of our sun’s luminosity. But the three sun view from the planet’s surface would be eerily beautiful.
Previous spectral analysis of the system found it to be different in chemical make up than our sun; the system has a low abundance of heavy elements, such as iron, silicon, and carbon (what’s known as a star’s metallicity, a general term indicating any elements other than hydrogen and helium) that are necessary to form planets. Thus the recent discovery of this Super Earth comes as a bit of a surprise.
However, in recent years, some astronomers and astrophysicists are beginning to re-think this notion, as other red dwarfs have been found to be hosts to a good many exoplanets (including those orbiting the red dwarf Gliese 581, whose habitable zone planet Gliese 581c, also a super Earth at 5 Earth masses, was discovered in 2007, by Swiss astronomer Stephane Udry and team).
Some astronomers associated with the study are saying that this discovery came “too easily, too quickly.”
Discoveries of candidate exoplanets in such small star systems may mean that habitable planets are more common than thought, or, that habitable planets may exist in a wider variety of stellar environments than previously supposed.
The detailed findings of the study are to be published in Astrophysical Journal Letters later this month.
Some source material for this article came from the Sci Am article ‘Newfound Alien Planet Is Best Candidate Yet to Support Life, Scientists Say’
Top image: (An artist’s conception of the alien planet GJ 667C c, which is located in the habitable zone of its parent star) Credit: Carnegie Institution for Science (source: the Sci Am webpage linked above)
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