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Discovered planet may have ocean like Earth

IN a discovery that one expert called "extraordinary," European astronomers reported finding one planet close to Earth's size in a different solar system and realizing that another planet could possibly sustain a large ocean.

European researchers said on Tuesday that not only had they found the smallest exoplanet ever, called Gliese 581 e, but they realized that a neighboring planet discovered earlier, Gliese 581 d, was in the prime habitable zone for potential life.

"The Holy Grail of current exoplanet research is the detection of a rocky, Earth-like planet in the 'habitable zone,'" said Michel Mayor, an astrophysicist at Geneva University in Switzerland.

Exoplanets are planets outside our solar system. Gliese 581 e is only 1.9 times the size of Earth - while previous planets found outside our solar system are closer to the size of massive Jupiter, which NASA says could swallow more than 1,000 Earths.

Gliese 581 e sits close to the nearest star, making it too hot to support life. Still, Mayor said its discovery in a solar system 20 light years away from Earth is a "good example that we are progressing in the detection of Earth-like planets."

Scientists also discovered that the orbit of planet Gliese 581 d, which was found in 2007, was located within the "habitable zone" - a region around a sun-like star that would allow water to be liquid on the planet's surface, Mayor said at a news conference on Tuesday at the University of Hertfordshire during the European Week of Astronomy and Space Science.

Water world

Fellow astronomer and team member Stephane Udry said Gliese 581 d is probably too large to be made only of rocky material, adding it was possible the planet had a "large and deep" ocean. "It is the first serious 'water-world' candidate," Udry said.

Mayor's main planet-hunting competitor, Geoff Marcy of the University of California, Berkeley, praised the find of Gliese 581 e as "the most exciting discovery" so far of exoplanets.

"This discovery is absolutely extraordinary," Marcy said, calling the discoveries a significant step in the search for Earth-like planets.

While Gliese 581 e is too hot for life "it shows that nature makes such small planets, probably in large numbers," Marcy commented. "Surely the galaxy contains tens of billions of planets like the small, Earth-mass one announced here."

Nearly 350 planets have been found outside our solar system but so far nearly all of them were unlikely to harbor life.

Most were too close or too far from their sun, making them too hot or too cold for life. Others were too big and likely to be uninhabitable gas giants like Jupiter.


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