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  • Jul 31, 2014
  • Updated: 6:07am
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SPACE

Planet twice the size of earth made of diamond

First known rocky planet 'fundamentally different' from our planet orbits Sun-like star

PUBLISHED : Friday, 12 October, 2012, 12:00am
UPDATED : Friday, 12 October, 2012, 4:03am

Forget the diamond as big as the Ritz. This one's bigger than planet Earth.

Astronomers have discovered a planet twice the size of our own made largely out of diamond, orbiting a star that is visible to the naked eye.

The planet, called "55 Cancri e", orbits a sun-like star in the constellation of Cancer and is moving so fast that a year there lasts a mere 18 hours.

Discovered by a US-Franco research team, its radius is twice that of Earth's but it is much denser, with a mass eight times greater.

It is also incredibly hot, with temperatures on its surface reaching 1,648 degrees Celsius.

"The surface of this planet is likely covered in graphite and diamond rather than water and granite," said Nikku Madhusudhan, the Yale researcher whose findings are due to be published in Astrophysical Journal Letters.

The study, made with Olivier Mousis at the Institut de Recherche en Astrophysique et Planetologie in Toulose, France, estimates that at least a third of the planet's mass, the equivalent of about three Earth masses, could be diamond.

Diamond planets have been spotted before but this is the first time one has been seen orbiting a star like our own Sun and studied in such detail.

"This is our first glimpse of a rocky world with a fundamentally different chemistry from Earth," Madhusudhan said. The discovery of the carbon-rich planet meant distant rocky planets could no longer be assumed to have chemical constituents, interiors, atmospheres, or biologies similar to Earth, he said.

David Spergel, an astronomer at Princeton University, said it was relatively simple to work out the basic structure and history of a star once you know its mass and age.

"Planets are much more complex. 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."

"Nearby" is a relative concept in astronomy. Any fortune-hunter not dissuaded by The Diamond as Big as the Ritz, F.Scott Fitzgerald's jazz age morality tale of thwarted greed, will find Cancri e about 40 light years, or 230 trillion miles, from Park Avenue.

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