Theorists believed such a world couldn't form because anything so hefty would grab hydrogen gas as it grew and become a Jupiter-like gas giant. This planet, though, is all solids and much bigger than previously discovered "super-Earths," making it a "mega-Earth."
Astronomer Xavier Dumusque of the Harvard-Smithsonian Center for Astrophysics (CfA), who led the data analysis and made the discovery, said they were very surprised when they realized what they had found.
CfA researcher Dimitar Sasselov, director of the Harvard Origins of Life Initiative, said this is the Godzilla of Earths but unlike the movie monster, Kepler-10c has positive implications for life.
The newfound mega-Earth, Kepler-10c, circles a Sun-like star once every 45 days. It is located about 560 light-years from Earth in the constellation Draco. The system also hosts a 3-Earth-mass "lava world," Kepler-10b, in a remarkably fast, 20-hour orbit.
epler-10c was originally spotted by NASA's Kepler spacecraft. Kepler finds planets using the transit method, looking for a star that dims when a planet passes in front of it. By measuring the amount of dimming, astronomers can calculate the planet's physical size or diameter. However, Kepler can't tell whether a planet is rocky or gassy.
Kepler-10c was known to have a diameter of about 18,000 miles, 2.3 times as large as Earth. This suggested it fell into a category of planets known as mini-Neptunes, which have thick, gaseous envelopes.