September 30, 2010

Potentially Habitable ‘Goldilocks’ Planet Discovered

Researchers from the University of California (UC) Santa Cruz and the Carnegie Institution for Science have discovered a new, roughly Earth-sized planet that they believe could sustain life, representatives from both educational institutions announced on Wednesday.

The investigative team discovered the new planet in a "habitable zone" (an area located at the right distance from a star in order to receive just enough stellar energy to maintain liquid water at or near the surface of the planet) near the red dwarf star Gliese 581, located approximately 20 light years from our solar system. The planet, which has three times the mass of our home world, was the result of 11 years of research conducted at Hawaii's W.M. Keck Observatory.

The research, which was sponsored by NASA and the National Science Foundation (NSF) and published in the Astrophysical Journal, "suggests that the fraction of stars in the Milky Way harboring potentially habitable planets could be greater than previously thought--as much as a few tens of percent," according to a Carnegie Institution press release.

Furthermore, according to a UC Santa Cruz statement, if the finding is in fact confirmed, the newly discovered planet "would be the most Earth-like exoplanet yet discovered and the first strong case for a potentially habitable one."

"Our findings offer a very compelling case for a potentially habitable planet," survey co-leader Steven Vogt, professor of astronomy and astrophysics at UC Santa Cruz, said. "The fact that we were able to detect this planet so quickly and so nearby tells us that planets like this must be really common."

The researchers report that the planet, dubbed Gliese 581g, is between 3.1 and 4.3 Earth masses, has a circular orbit lasting nearly 37 days, and an estimated radius of 1.2 to 1.5 Earth radii. Co-authors Vogt and Paul Butler of the Carnegie Institution note that the planet is likely a rocky planet that has just enough gravity to maintain an atmosphere.

It was discovered along with a second, uninhabitable planet, by the research team--bringing the total number of worlds found orbiting Gliese 581 to six, all of which have nearly circular orbits. Previously, two additional planets were discovered just outside the habitable zone--one would be too hot, and the other too cold to maintain life. Gliese 581g, however, is "just right," according to Vogt, earning it the nickname "The Goldilocks Planet."

In an interview with AP Science Writer Seth Borenstein, Jim Kasting of Penn State University called the newly discovered world a "pretty prime candidate" for harboring life, and the rapid discovery of the planet has scientists hopeful that other, similar findings will soon follow.

"If these are rare, we shouldn't have found one so quickly and so nearby," said Vogt. "The number of systems with potentially habitable planets is probably on the order of 10 or 20 percent, and when you multiply that by the hundreds of billions of stars in the Milky Way, that's a large number. There could be tens of billions of these systems in our galaxy."


Image Caption: The star Gliese 581 hosts an Earth-sized planet (foreground) that orbits in the star's habitable zone. Artwork by Lynette Cook.


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