On Monday, scientists announced that Kepler-10c, a planet discovered in 2011, is a planet like no other, earning itself the nickname "mega-Earth."

The team made its announcement at an American Astronomical Society press conference, according to a press release by the Harvard-Smithsonian Center for Astrophysics. The planet weighs 17 times more than Earth. Originally, scientists thought a planet like Kepler-10c was impossible "because anything so hefty would grab hydrogen gas as it grew and become a Jupiter-like gas giant," the press release says.

"We were very surprised when we realized what we had found," Xavier Dumusque, CfA astronomer who led the data analysis, said via the press release.

Kepler-10c was discovered with NASA's Kepler spacecraft, which specializes in finding planets by hunting for stars that appear dimmer when a planet passes it. Astronomers can determine a planet's size based on how much the stars dim. Kepler-10c was said to have an 18,000-mile-long diameter, which is 2.3 larger than Earth and implied that the planet was like a "mini-Neptune," enveloped in thick gas. Upon using the HARPS-North instrument on the Telescopio Nazionale Galileo in the Canary Islands, however, scientists discovered that the planet was bigger than they thought and made of rocks and solids rather than gas.

"Kepler-10c didn't lose its atmosphere over time. It's massive enough to have held onto one if it ever had it," Dumusque explained. "It must have formed the way we see it now."

The mega-Earth completes a circle around a star like the Sun every 45 days. It lies in the Draco constellation, about 560 light-years away from Earth.

The planet's unique attributes give new hope for extraterrestrial life.

"This is the Godzilla of Earths!" Dimitar Sasselov, CfA researcher and director of the Harvard Origins of Life Initiative, said via the press release."But unlike the movie monster, Kepler-10c has positive implications for life."

Kepler-10c also suggests that astronomers should not forget to look around old stars for planets similar to Earth.

"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," Sasselov added.

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Follow Scharon Harding on Twitter: @ScharHar.

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