Stargazers dazzled by diamond planet
Forget the Cullinan Diamond. This diamond's bigger than planet Earth.
Orbiting a star visible to the naked eye is a planet twice the size of Earth made largely of diamond, astronomers have discovered.
The rocky 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-French research team, its radius is twice that of Earth's but it is much more dense, with a mass eight times greater. It is also incredibly hot, with temperatures on its surface reaching 1648C.
"The surface of this planet is probably covered in graphite and diamond instead of water and granite," said Nikku Madhusudhan, the Yale researcher whose findings are due to be published in the journal Astrophysical Journal Letters.
The study - with Olivier Mousis, at the Institute for Research in Astrophysics and Planetary Science, in Toulose, France - estimates that at least a third of the planet's mass, the equivalent of about three Earth masses, might be diamond.
Diamond planets have been spotted before but this is the first time one has been seen orbiting a sun-like star and studied in such detail.
"This is our first glimpse of a rocky world with a fundamentally different chemistry from that of Earth," Madhusudhan said, adding that 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's.
David Spergel, an astronomer at Princeton University, said it was relatively simple to work out the basic structure and history of a star once its mass and age were known.
"Planets are much more complex. This diamond-rich super-Earth is probably just one example of the rich set of discoveries that awaits us as we begin to explore planets around nearby stars."
"Nearby" is a relative concept in astronomy.
Any fortune-hunter would have to make a journey of about 40 light years, or 145trillion kilometres, from Earth.