Scientists discover a 'mega-Earth' that is 2.3 times larger than Earth

First spotted by NASA’s Kepler space telescope, The newly discovered planet "Kepler-10c" dubbed a "mega-Earth" is about 2.3 times larger than Earth, 17 times as much mass as Earth, meaning it must be filled with rock and other materials much heavier than hydrogen and helium.

Earth, by comparison, is only around 4.5 billion years old. The Kepler-10 star system is an estimated 11 billion years old.

The planet circles its Sun-like parent star, located in the constellation Draco, every 45 days.

Kepler-10c, was previously thought to fall into the category of "mini-Neptune" planets that have an icy core surrounded by a thick gassy envelope. Its sister planet, Kepler-10b, was the first rocky planet found beyond the solar system. 

"We were very surprised when we realised what we had found", said astronomer Dr Xavier Dumusque.

“Kepler-10c is a big problem for the theory,” astronomer Dimitar Sasselov, director of the Harvard Origins of Life Initiative, told Discovery News. “It’s nice that we have a solid piece of evidence and measurements for it because that gives motivations to the theorists to improve the theory,” he said.

Scientists aren’t sure how mega-Earths, or their diminutive cousins, super-Earths, form, nor why our solar system has nothing in between the largest rocky planet, Earth, and the smallest gas giant, Neptune.