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This planet would definitely be a girl's best friend

| Thursday, Oct. 11, 2012, 7:22 p.m.

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

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

In fact, this is not the first diamond planet ever discovered, but it is the first found orbiting a sun-like star and whose chemical makeup has been specified.

The discovery means that distant rocky planets can no longer be assumed to have chemical constituents, interiors, atmospheres or biologies similar to those of Earth, said lead researcher Nikku Madhusudhan, a Yale postdoctoral researcher in physics and astronomy.

The planet was first observed last year — but researchers initially assumed it was similar in its chemical make-up to Earth.

It was only after a more detailed analysis that the French-American research team determined the planet, dubbed ‘55 Cancri e,' is vastly different from our own.

The planet “appears to be composed primarily of carbon (as graphite and diamond), iron, silicon carbide, and, possibly, some silicates,” the authors wrote in a statement ahead of their findings' publication in the journal Astrophysical Journal Letters.

“The surface of this planet is likely covered in graphite and diamond rather than water and granite,” Madhusudhan noted.

In fact, the planet appears to have no water at all. And as much as a third of the planet's substantial mass could be made of diamond, a super-dense compound of carbon.

In comparison, the Earth's interior is rich in oxygen and very poor in carbon, explained study co-author Kanani Lee of Yale.

The researchers estimated the planet's radius with data collected while it was transiting in front of its star.

That information, combined with an estimate of its mass, was used to model the planet's chemical composition, based on a calculation of just what elements and compounds could result in that specific size and mass.

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