New Type of Massive, Rocky Planet Discovered in Our Universe: The Mega-Earth

There's a new type of planet in our universe--and it's a big one. Astronomers have discovered a rocky world weighing 17 times as much as Earth, making it much larger than the previously-known "super-Earth." As hefty as it is, this new type of planet is now being called a "mega-Earth."

"This is the Godzilla of Earths!" said Dimitar Sasselov, CfA researcher, in a news release. "But unlike the movie monster, Kepler-10c has positive implications for life."

The newly discovered mega-Earth is called Kepler-10c. It's located about 560 light-years from Earth in the constellation Draco, and orbits its sunlike star once every 45 days.  

The planet was originally spotted by NASA's Kelpler spacecraft, which estimated that the planet had a diameter of about 18,000 miles, which is about 2.3 times as large as Earth. That's why at first, astronomers believed it to fall into a category of planets called mini-Neptunes, which have thick, gaseous envelopes. On closer examination, though, it turned out that this wasn't the case.

The astronomers used the HARPS-North instrument in the Canary Islands to measure the mass of Kepler-10c. They found that it weighed 17 times as much as Earth, which is far more than expected. This meant that the planet had a dense composition of rocks and other solids. That's not all, either. The planet also didn't lose its atmosphere over time; instead, it's massive enough to hold onto it.

Kepler-10c has massive implications for the history of the universe and the possibility of life. Since the planet's system is about 11 billion years old, it formed less than 3 billion years after the Big Bang. This means it shows an early planetary system and reveals that the universe was able to form huge planets even during a time when elements were scarce.

"Finding Kepler-10c tells us that rocky planets could form much earlier than we thought," said Sasselov in a news release. "And if you can make rocks, you can make life."

The findings were presented at a meeting of the American Astronomical Society.