Astronomers Discover 'Godzilla of Earths'

A new planet has been discovered that astronomers are calling the "mega-Earth."

Weighing 17 times as much as Earth, this massive, rocky world called Kepler-10c orbits a sunlike star about 560 light-years from Earth.

"This is the Godzilla of Earths!" Harvard-Smithsonian Center for Astrophysics (CfA) researcher Dimitar Sasselov, director of the Harvard Origins of Life Initiative, said in a statement. "But unlike the movie monster, Kepler-10c has positive implications for life."

As the name suggests, Kepler-10c was originally spotted by NASA's Kepler spacecraft. Theorists had always thought that any planet that large would pull so much hydrogen on to itself that it would look more like a Neptune or a Jupiter.

"We were very surprised when we realized what we had found," said CfA astronomer Xavier Dumusque.

Kepler technology is able to find new worlds by looking for the tiny dip in light as they pass in front of their parent stars.

The technique gives a diameter - in this case, 18,000 miles (29,000km), or just over two times the width of Earth - but not a mass. For that, astronomers looked at 10c with the Harps-North instrument on the Telescopio Nazionale Galileo in the Canary Islands. It extracts a mass measurement by examining the gravitational interaction between the planet and its host star.

Combined with the diameter, the mass number - 17 times as much as Earth - showed that Kepler-10c cannot be a gaseous world but must be comprised of very dense material like rocks and other solids.

Interestingly, the age of the host star is about 11 billion years old, which is early in the evolution of the Universe (not long after the Big Bang, relatively speaking) when generations of exploding stars supposedly had not had enough time to make the heavy elements needed to construct rocky planets.

"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 said.

The team's finding was presented today in a press conference at a meeting of the American Astronomical Society.