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Astronomers discover type of rocky planet much bigger than Earth

Published on Jun 3, 2014 6:53 AM
The newly discovered "mega-Earth" Kepler-10c dominates the foreground in this artist's conception released by the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts on June 2, 2014. -- PHOTO: REUTERS

BOSTON (REUTERS) - Astronomers have discovered a new type of rocky planet beyond the solar system that weighs more than 17 times as much as Earth while being just over twice the size, scientists said on Monday.

The so-called "mega-Earth" circles a very old star called Kepler-10, which is located about 560 light-years away from Earth in the constellation Draco.

The discovery, announced at the American Astronomical Society meeting in Boston, was a surprise since planets that big were believed to be mostly gas, not solid rocky bodies like Earth or Mars, said physicist Dimitar Sasselov, director of the Harvard Origins of Life Initiative.

Scientists do not yet understand how the planet, known as Kepler-10c, formed. It has a diameter of about 29,000km, 2.3 times greater than Earth's. "A mega-Earth is a lot of solids concentrated in the same place without any gas. That is a problem because our understanding for how planets form requires the solids to get together in an environment where almost 99 per cent of the mass... is hydrogen and helium," Sasselov told reporters at a press conference.

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