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Beyond Earthly Skies

Mega-Earths and Chthonian Planets

7 Aug 2014, 22:00 UTC
Mega-Earths and Chthonian Planets
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Over the years, the search for exoplanets has shown that exoplanets vary enormously in size, mass, composition, and nearly every conceivable parameter. Many of the discoveries were surprising and unexpected. Even so, rocky planets are not known to exceed ~10 times the mass of Earth. It is believed that a more massive rocky planet would have such an enormous gravitational pull that it would accrete a gas envelope during formation and end up either as an ice giant like Neptune or a gas giant like Jupiter. All that changed when Dumusque et al. (2014) reported the discovery of the first bona fide rocky planet with a mass exceeding 10 times the mass of Earth. “We were very surprised when we realized what we had found,” says astronomer Xavier Dumusque of the Harvard-Smithsonian Center for Astrophysics, who led the data analysis and made the discovery.r;"> Figure 6: Artist’s impression of a high-density solid planet.A study by Seager et al. (2007) suggests that massive O and B stars with 5 to 120 times the mass of the Sun can have very hefty protoplanetary disks containing large amounts of heavy elements. The strong UV radiation and stellar winds from these stars can photo-evaporate ...

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