THE planet, which takes just 18 hours to travel round its star, is believed to have a surface covered by graphite and diamond instead of water and granite
A «SUPER-Earth» orbiting a nearby star may have a diamond-encrusted surface, scientists believe.
The planet, called 55 Cancri e, is twice as big and eight times as massive as the Earth.
It is one of five planets orbiting the Sun-like star, 55 Cancri, 40 light years away in the constellation of Cancer.
The planet whips around its star in 18 hours and is blisteringly hot, with a surface temperature of around 2,150C.
Dr Nikku Madhusudhan, from Yale University in the US, who has studied the diamond planet, said: «This is our first glimpse of a rocky world with a fundamentally different chemistry from Earth.
«The surface of this planet is likely covered in graphite and diamond rather than water and granite.»
Astronomers discovered the planet last year by spotting the minute dimming of light as 55 Cancri e passed in front of its parent star.
After calculating the planet’s size and mass, scientists were able to make inferences about its chemical make-up.
Their research, due to appear in the Astrophysical Journal Letters, suggests that at least a third of the planet could consist of diamond.
Professor David Spergel, from Princeton University in the US, said: «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.»