for National Geographic News
Yesterday astronomers announced the discovery of the most Earthlike planet ever detected outside of our solar system.
The discovery raises the prospect that the Milky Way galaxy (see photo) is full of planets that could harbor life, the scientists say.
Five times as massive as Earth, the newfound planet orbits its parent star once every ten years. The planet is as about three times as far from its star as Earth is from the sun.
The newfound planet's host star is a red dwarf with about one-fifth the mass of our sun. Red dwarfs have cooler surface temperatures and are smaller, dimmer, and less massive than the sun. They're also the most common stars in our galaxy.
The planet, named OGLE-2005-BLG-390Lb, is located more than 20,000 light-years away in the constellation Sagittarius, near the center of the Milky Way.
The discovery team says the mass of the planet, its distance from its star, and the brightness of its star suggest that the planet has a rocky surface buried beneath frozen oceans. The distant world also likely has a thin atmosphere.
Scientists believe the surface of OGLE-2005-BLG-390Lb is a frigid 364°F (220°C). That's about as cold as the surface of Pluto.
"The only substances able to form a planet of that size, at that temperature, are rock and ice," Andrew Williams, an astronomer at the Perth Observatory in Australia, said in an email interview.
"And during formation, the rock, being heavier, would have sunk to the middle. Pluto and many of Saturn's and Jupiter's moons are similar," he added.
Williams is one of 73 co-authors who describe the discovery in the January 26 issue of the science journal Nature.
The planet is likely too cold to harbor life, but the technique researchers used to find it may one day detect a habitable Earthlike planet, according to the astronomers.
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