Scientists have previously discovered "super-Earths," planets roughly ten-times the mass of Earth. But most astronomers assumed planets any bigger would be gas giants like Jupiter.
But Kepler-10c -- announced Monday at the 224th American Astronomical Society meeting in Boston -- isn't gaseous, it's rocky.
"This is the Godzilla of Earths!" said Dimitar Sasselov, a researcher at the Harvard-Smithsonian Center for Astrophysics (CfA) and the director of the Harvard Origins of Life Initiative. "But unlike the movie monster, Kepler-10c has positive implications for life."
The exoplanet boasts a diameter of about 18,000 miles, which makes it 2.3-times bigger than Earth. But Kepler-10c weighs 17 times as much, thanks to its super dense rocky core.
The researchers at CfA -- who use information collected by Kepler to find and study potential life-sustaining exoplanets -- say Kepler-10c and the rest of its solar system is roughly 11 billion years old, meaning it formed less than 3 billion years after the Big Bang.
"Finding Kepler-10c tells us that rocky planets could form much earlier than we thought," Sasselov said. "And if you can make rocks, you can make life."
Still, Kepler-10c itself is highly unlikely to harbor living organisms. It's much too close to its parent star, a red dwarf that lies 560 light-years away from Earth in the constellation Draco. The surface of Kepler-10c is likely roasted from its close proximity to its sun.