'Godzilla' of earths may have harboured life once?

A 'Godzilla' planet that is 17 times the size of our earth has been discovered, leaving the scientific fraternity in shock as anything so hefty would grab hydrogen gas as it grew and become a Jupiter-like gas giant.

This planet, though, is all solids and much bigger than previously discovered "super-earths" - making it a "mega-earth".

"We were very surprised when we realised what we had found," said astronomer Xavier Dumusque of the Harvard-Smithsonian Center for Astrophysics (CfA), who made the discovery by using NASA's Kepler spacecraft.

"This is the 'Godzilla' of earths. But unlike the movie monster, it has positive implications for life," added Dimitar Sasselov, director of the Harvard Origins of Life Initiative.

The new-found Kepler-10c circles a sunlike star once every 45 days.

It is located about 560 light-years from earth in the constellation Draco and has a remarkably fast, 20-hour orbit.

Kepler-10c was known to have a diameter of about 18,000 miles - 2.3 times as large as the earth.

The team used the HARPS-North instrument on the Telescopio Nazionale Galileo (TNG) in the Canary Islands to measure the mass of Kepler-10c.

They found that it weighed 17 times as much as the earth - far more than expected.

This showed that Kepler-10c must have a dense composition of rocks and other solids.

"Kepler-10c did not lose its atmosphere over time. It is massive enough to have held onto one if it ever had it. It must have formed the way we see it now," Dumusque explained.

The discovery that Kepler-10c is a mega-earth also has profound implications for the history of the universe and the possibility of life.

The Kepler-10 system is about 11 billion years old, which means it formed less than three billion years after 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 noted.

The finding were presented in a press conference at a meeting of the American Astronomical Society (AAS).