Hot, rocky exoplanets are the scorched cores of former gas giants | Science News

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Hot, rocky exoplanets are the scorched cores of former gas giants

The planets are nestled close to their stars, where stellar winds may have blown ancient atmospheres away

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1:58pm, October 31, 2017
55 Cancri e

NOT LIKE HOME  Rocky super-Earth 55 Cancri e, seen in this artist’s illustration, is about Earth’s size, but a new study suggests it and other similar hot exoplanets probably formed in a completely different way than Earth did.

Earth may not provide the best blueprint for how rocky planets are born.

An analysis of planets outside the solar system suggests that most hot, rocky exoplanets started out more like gassy Neptunes. Such planets are rocky now because their stars blew their thick atmospheres away, leaving nothing but an inhospitable core, researchers report in a paper posted online October 15 at arXiv.org. That could mean these planets are not as representative of Earth as scientists thought, and using them to estimate the frequency of potentially life-hosting worlds is misleading.

“One of the big discoveries is that Earth-sized, likely rocky planets are incredibly common, at least on hotter orbits,” says planetary scientist Eric Lopez of NASA’s Goddard Space Flight Center in Greenbelt, Md., who wasn’t involved in the study. “The big question is, are those hot exoplanets telling us anything about the frequency

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