The universe's planetary "zoo" has just had a new species added, astrophysicists say, a kind of planet never seen before that's been dubbed a "mega-Earth," larger than our planet but with many similarities.
One of those similarities could be the potential of supporting some form of life, despite its immense larger-than-Earth mass and diameter, they say.
"This is the Godzilla of Earths!" researcher Dimitar Sasselov of the Harvard-Smithsonian Center for Astrophysics says. "But unlike the movie monster, Kepler-10c has positive implications for life."
The mega-Earth circles the sunlike star Kepler-10, located around 560 light years away, once every 45 days. It is in the constellation Draco.
Its diameter is more than twice that of the Earth, but what really surprised the researchers is its apparent mass -- 17 times that of Earth.
Scientists had previously believed a planet of such size should not even exist as a solid world, but rather should be comprised mostly of gas, like Jupiter and the other "gas giants" of our own solar system.
"Kepler-10c is a big problem for the theory," of planetary formation, Sasselov says. "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."
The existence of Kepler-10c as a mega-Earth has researchers saying they may have to reconsider the universe's history and the possibility of life on different kinds of planets.
The Kepler-10 planetary system is around 11 billion years old, meaning it formed when the universe was just 3 billion years past the Big Bang.
"Finding Kepler-10c tells us that rocky planets could form much earlier than we thought. And if you can make rocks, you can make life," Sasselov says.
The upshot of this, the researchers say, is that older stars shouldn't be ruled out in the search for Earth-like planets, which will increase the number of candidates of potentially habitable worlds in our cosmic environment.
Even Sasselov says that just five years ago he would have argued it was a waste of time to look for rocky, Earth-like planets around older stars, but Kepler-10C has changed his mind.
Still, the researchers admit, Kepler-10c is not the best kind of candidate. It orbits too near to its parent star to retain liquid water at its surface, and its crushing gravity means any water it possessed it likely tied up in its minerals or squeezed into a solid form.
"I call it a solid planet," says Sasselov, "rather than a rocky planet."
