At a meeting of the American Astronomical Society today, a team of astronomers announced that they'd discovered a new planet—a rocky world weighing 17 times the size of Earth that they've dubbed "mega-Earth."
The discovery comes as a pleasant surprise to space enthusiasts, as it was previously believed that planets so big couldn't form because they would pull in hydrogen gas as they grew and turn into Jupiter-like gas giants. The mega-Earth is all solids.
The newfound mega-Earth, Kepler-10c, circles a sunlike star once every 45 days. It is located about 560 light-years from Earth in the constellation Draco. The system also hosts a 3-Earth-mass "lava world," Kepler-10b, in a remarkably fast, 20-hour orbit.
The largest comparable planets had been called "super-Earths" and though the new mega-Earth is the first of its kind, other discoveries like this could be in the future.
From the Harvard-Smithsonian Center for Astrophysics:
Also presenting at AAS, CfA astronomer Lars A. Buchhave found a correlation between the period of a planet (how long it takes to orbit its star) and the size at which a planet transitions from rocky to gaseous. This suggests that more mega-Earths will be found as planet hunters extend their data to longer-period orbits.
Why is that an important point to note? As Center for Astrophysics researcher Dimitar Sasselov puts it, "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."