Astronomers say they have discovered a planet twice the size of Earth that is made mostly of diamond.

Planet 55 Cancri e orbits a star similar to our sun 40 light years away in the constellation of Cancer, Reuters reports. It s orbit is so fast, one year there lasts just 18 hours. The surface temperatures are estimated at 3,900 degrees Fahrenheit.

A study to be published in the journal Astrophysical Journal Letters finds that at least a third of the planet is believed to be made of diamond.

While it s not the first diamond planet ever discovered, it is the first time one has been seen orbiting a sun-like star.

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