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Earth-y orb found in habitable zone: size, position make planet promising prospect for life.

Inching ever closer toward the goal of finding another Earth, scientists have announced the most promising extraterrestrial incubator so far: a planet of at least 4.5 Earth masses, orbiting its star in the region where liquid water can exist.

Called GJ 667Cc, the super-Earth circles one member of a triple-star system shining 22 light-years from Earth near the curving tail of the constellation Scorpius.

Unlike other recent tantalizing discoveries, the planet is both well within its star's life-friendly zone and just about the right size to host life as we know it. But that doesn't mean GJ 667Cc is habitable, scientists caution.

"It's definitely the best candidate," says astronomer Abel Mendez of the University of Puerto Rico at Arecibo. "If it's rocky, then it will be more compelling evidence that this is a true habitable planet."

An international team spotted the newly announced planet in data from the High Accuracy Radial Velocity Planet Searcher, or HARPS, a Swiss-led project that monitors stars for the gentle gravitational tugs produced by orbiting planets. A star's wobble reveals the mass of a planet circling it. But scientists don't know its radius, how dense the orb is or what it might be made of.

Astronomers debate who really discovered GJ 667Cc; this latest announcement comes from a team with a new method for processing HARPS data. Guillem Anglada-Escude of the University of Gottingen in Germany and colleagues sniffed out the signatures of as many as three planets circling the star GJ 667C, reporting the results in an upcoming Astrophysical Journal Letters.

The closest-in planet, also a super-Earth, zooms around the star every 7.2 days. The second planet--the one of interest--dawdles a bit, with a 28.15-day orbit. The third signature could be a planet on a 75-day orbit, but could also be just an artifact of the star's activity.

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Title Annotation:Atom & Cosmos
Author:Drake, Nadia
Publication:Science News
Article Type:Brief article
Geographic Code:1USA
Date:Mar 10, 2012
Words:318
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