The planet, known as Kepler-47c, is a gas giant and therefore probably not suitable for life as we know it. But its existence hints that smaller, rockier worlds may inhabit other two-star systems' habitable zones —that just-right range of distances where liquid water can exist.

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The Kepler-47 system, whose discovery was announced Tuesday (Aug. 28), dwells about 5,000 light-years away, in the constellation Cygnus (The Swan). It is a close binary system, with two stars orbiting near each other at its center. Around these stars whirl two planets known as Kepler-47b and Kepler-47c.

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 Kepler-47c, which appears to be slightly larger than Uranus, is the outer world. It takes the planet 303 days to complete an orbit, placing it squarely in the system's habitable zone. (Kepler-47b is a bit smaller than its planetary sibling but much closer-in, making it likely too hot to host life.)

Kepler-47c itself is likely not a good bet to support life. But any large moons of the planet — if they exist — would be very intriguing to astrobiologists, said study co-author William Welsh at San Diego State University.

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 Indeed, Kepler's main mission is to determine just how commonly Earth-size planets occur in their stars' habitable zones throughout the galaxy. The telescope detects alien planets by flagging the telltale brightness dips caused when they cross in front of, or transit, their stars' faces from the instrument's perspective..

"I expect that the transits of an Earth-sized planet will be very hard to spot by eye, so we will need to refine our automated search programs to work for binary systems," Orosz said. "As Kepler gets more and more data, the chances go up that we can identify the smaller transits due to terrestrial planets."

Newfound 'Tatooine' Alien Planet Bodes Well for E.T. Search



A newly discovered alien planet may be one of the top contenders to support life beyond Earth, researchers say.

The newfound world, a "super Earth" called Gliese 163c, lies at the edge of its star's habitable zone — that just-right range of distances where liquid water could exist.

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Gliese 163c was one of two alien planets found orbiting the star Gliese 163, which lies about 50 light-years from Earth in the Dorado constellation. The team found indications of a third planet as well but cannot confirm it at this time.

Weighing in at about seven times the mass of Earth, Gliese 163c could be a rocky planet, or it could be a dwarfed gas giant, researchers said.

"We do not know for sure that it is a terrestrial planet," Bonfils said. "Planets of that mass regime can be terrestrial, ocean, or Neptune-like planets."

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In the meantime, Bonfils and his team intend to use HARPS to continue their search for planets that could be ripe for life, hoping to find one that may allow astronomers to study it today rather than tomorrow.

"Although it is nice to build the sample of possibly habitable planets that will be observed with the next generation of telescopes, it would be even better if we could find a planet one could characterize with today's observatories," Bonfils said.

Newfound Alien Planet a Top Contender to Host Life