Hot Planet Seen as Earth’s Twin in Size, Sceintists Find

A planet located about 400 light years away has a similar density and size to Earth yet is much hotter and can’t support life, two studies found.

Kepler-78b, discovered earlier this year using data from the National Aeronautics and Space Administration’s Kepler Space Telescope, is probably made of rock and iron like Earth, according to two studies in the journal Nature. The planet, which orbits a star in 8.5 hours rather than a sun in a year like Earth, is the smallest for which the radius and mass are accurately known, the researchers said.

“Every new detection is a piece of a larger puzzle,” said Francesco Pepe, lead author of one of the papers and an associate professor of astronomy at Geneva University, in an e-mail. “All these pieces of puzzle are important to get a global picture of how planets form, live and die.”

Researchers from Geneva University and the University of Hawaii at Manoa in Honolulu determined the mass of Kepler-78b and then its density.

Pepe said they found that the planet’s mass was about 1.86 times that of Earth, while its density was nearly identical to Earth’s, implying the planet is made up of iron and rock. Andrew Howard, lead author of the University of Hawaii paper, found that Kepler-78b’s mass was 1.69 times that of Earth and its density was similar to Earth’s as well. Both authors said their findings released yesterday weren’t significantly different.

Drake Deming, a professor in the Department of Astronomy at the University of Maryland in College Park, wrote in an accompanying article that the results show that Kepler-78b is “a virtual twin of Earth by astronomical standards.”

“Kepler-78b thereby foreshadows leaps forward in the search of life beyond the Solar System,” he wrote.

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