Forget “super-Earths.” Those giant rocky planets are old and busted. Today astronomers announced they had discovered a much bigger “mega-Earth,” a rocky planet 17 times heavier than our earth.
The mega-Earth Kepler-10c is so big that astronomers previously thought such a planet was impossible, because it was theorized something with that much mass would have drawn hydrogen gas to itself in its creation and became a gas giant. But there it is, 560 light-years away in the constellation Draco.
“This is the Godzilla of Earths!” said Harvard-Smithsonian Center for Astrophysics (CfA) researcher Dimitar Sasselov, director of the Harvard Origins of Life Initiative. “But unlike the movie monster, Kepler-10c has positive implications for life.”
The discovery of Kepler-10c will require scientist to recalculate the odds for finding life in the universe.
Because only hydrogen and helium existed in the early universe, heavier elements needed to make rocky planets had to be formed within stars and scattered as those stars exploded, a lengthy process. But Kepler-10c is in a system that’s 11 billion years old, which means it formed less than 3 billion years after the Big Bang.
And that means rocky planets were able to form billions of years earlier than thought possible, meaning they may exist around old stars that planet-hunters had previously ruled out.
“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,” says Sasselov.
Kepler-10c was originally spotted by NASA’s Kepler spacecraft, but it’s huge 18,000 mile diameter gave the initial impression that it was a type of gas-enveloped planet known as a “mini-Neptune.”
After studying it with the HARPS-North instrument on the Telescopio Nazionale Galileo (TNG) in the Canary Islands, the team found that Kepler 10c had a mass that suggested it had to be made of rock and other solids.
“Kepler-10c didn’t lose its atmosphere over time. It’s massive enough to have held onto one if it ever had it,”said astronomer Xavier Dumusque of the Harvard-Smithsonian Center for Astrophysics (CfA), who led the data analysis and made the discovery. “It must have formed the way we see it now.”
And its likely that there are more mega-Earths out there. Recent research by CfA astronomer Lars A. Buchhave suggests more mega-Earths will be found as planet hunters extend their data to longer-period orbits.
Image: Artists conception of the mega-Earth from CfA