Astronomers have discovered the heaviest planet yet that's predominantly rocky, a hefty body 17 times more massive than Earth. Called Kepler-10c, the planet orbits a star that is similar to the sun, though nearly twice as old, and located about 560 light-years away in the constellation Draco.

The exoplanet, which has been dubbed a “mega-Earth,” could be the first of a new class of massive rocky planets found at more distant orbits from their stars, said the astronomers who announced their discovery this week at the American Astronomical Society meeting in Boston.