astroengine (1577233) writes "Meet 'mega-Earth' a souped-up, all-solid planet that, according to theory, should not exist. First spotted by NASA's Kepler space telescope, the planet is about 2.3 times larger than Earth. Computer models show planets that big would be more like Neptune or the other gas planets of the outer solar system since they would have the gravitational heft to collect vast amounts of hydrogen and helium from their primordial cradles. But follow-up observations of the planet, designated as Kepler-10c, show it has 17 times as much mass as Earth, meaning it must be filled with rock and other materials much heavier than hydrogen and helium. 'Kepler-10c is a big problem for the theory,' astronomer Dimitar Sasselov, director of the Harvard Origins of Life Initiative, told Discovery News. 'It's nice that we have a solid piece of evidence and measurements for it because that gives motivations to the theorists to improve the theory,' he said."