MANCHESTER, England, Aug. 25 (UPI) -- Australian astronomers say a planet seen orbiting a distant pulsar is likely composed mostly of crystalline carbon -- making it, in effect, a diamond planet.
Pulsars are small spinning stars that emit a beam of radio waves in pulses toward Earth.
Astronomers in Australia and at the University of Manchester in Britain say periodic changes in those pulses from the pulsar known as PSR J1719-1438 are due to the gravitational pull of a small companion object, orbiting the pulsar in a binary system at a distance of just 375,000 miles.
Despite its small size, astronomers say, the object has more mass than Jupiter.
"This high density of the planet provides a clue to its origin," Mathew Bailes of Australia's Swinburne University of Technology said in a release from the University of Manchester.
The astronomers say the "diamond planet" is all that remains of a once-massive star that has had most of its matter siphoned off toward the pulsar.
What remains is mostly carbon and oxygen, they said, and the "planet's" density means this material is certain to be crystalline -- in other words, a large part of the star may be similar to a diamond.
