First mega-Earth found

This huge, rocky exoplanet upends astronomers' ideas about how planets form

By Stephen Ornes, 08:53 AM June 16, 2014

The giant exoplanet, Kepler-10c, doesn't play by the rules. It has as much mass as Neptune — yet it’s made of rock, just like Earth. Astronomers are now calling it a “mega-Earth.” Our solar system’s massive planets, such as Jupiter and Saturn, are made from gas. And scientists used to think any planet that massive must also be made primarily of helium and hydrogen. But Kepler-10c is now forcing experts to throw such assumptions out the window.

Kepler-10c is one of two planets orbiting a sunlik...

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