Scientists have discovered a planet made of diamonds.
The strange alien world is roughly twice the size of Earth, eight times its mass and is orbiting a (relatively) near star.
"This is our first glimpse of a rocky world with a fundamentally different chemistry from Earth," said lead researcher Nikku Madhusudhan, from Yale.
"The surface of this planet is likely covered in graphite and diamond rather than water and granite."
The planet is called 55 Cancri E, and is one of five worlds in the system located just 40 light years from Earth in the constellation of Cancer.
Its composition was discovered after new details about its orbit - a year lasts just 18 hours on 55 Cancri E - and conditions on the planet (a super-hot 3,9000 degrees Fahrenheit) came to light.
Researchers are able to estimate its mass, and infer its chemical make-up from this and other information.
They now say it is mainly made of carbon (as graphite and diamond), iron and silicon carbide.
The discovery is not the first diamond planet to be discovered. A similar find was made in 2011, and there are likely many other worlds with a similar composition.
But the discovery will still force researchers to think differently about how alien worlds are made, the study said.
"The identification of a carbon-rich super-Earth means that distant rocky planets can no longer be assumed to have chemical constituents, interiors, atmospheres, or biologies similar to those of Earth," the researchers reported.
"This 'diamond-rich super-Earth' is likely just one example of the rich sets of discoveries that await us as we begin to explore planets around nearby stars."