Gem of a planet struck: study

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Astronomers claim that a planet orbiting a small fast spinning star, called a pulsar, is likely made of diamond. Pulsars are small spinning stars about 20 km in diameter – the size of a small city – that emits a beam of radio waves. As the star spins and the radio beam sweeps repeatedly over Earth, radio telescopes detect a regular pattern of radio pulses.

Researchers, from The University of Manchester as well as institutions in Australia, Germany, Italy, and the USA, noticed that the arrival times of the pulses were systematically modulated. They concluded that this was due to the gravitational pull of a small companion planet, orbiting the pulsar in a binary system.

But despite its small size, the planet has slightly more mass than Jupiter.

“This high density of the planet provides a clue to its origin”, said Professor Bailes.

The team thinks that the ''diamond planet'' is all that remains of a once-massive star, most of whose matter was siphoned off towards the pulsar.

“This remnant is likely to be largely carbon and oxygen, because a star made of lighter elements like hydrogen and helium would be too big to fit the measured orbiting times,” said Dr Michael Keith (CSIRO), one of the research team members.

The density means that this material is certain to be crystalline: that is, a large part of the star may be similar to a diamond.

The study has been published in the journal Science.