Kepler telescope spies rocky 'Mega-Earth'

Astronomers have discovered a surprising new planet, a rocky world with 17 times the mass of earth. There have been "super-earths" discovered before, but this one is in a league of its own. The scientists call it a "Mega-Earth".

Discovered by Nasa's Kepler Space Telescope and announced on Monday at an astronomy meeting in Boston, this new planet, officially named Kepler-10c, scrambles the equations that dictate how massive a rocky planet can be without ballooning into a Jupiter-like gas giant.

The theorists didn't see this coming. The orthodoxy was that, beyond about 10 earth masses, a planet would hold on to so much hydrogen gas that it would become like Jupiter or Saturn. Kepler-10c suggests plus-size planets can stay rocky, with clearly defined surfaces, rather than become gaseous and bloated.

That means there's more real estate out there for life as we know it on earth.

Kepler-10c is also very old, having formed about 11 billion years ago, less than three billion years after the birth of the universe. Rocky worlds weren't believed to have existed that long ago.

Kepler-10c, which orbits a star 560 light-years away in the constellation Draco, isn't likely to harbour life. It is too close to the parent star and the surface is thoroughly roasted.