A planet made of diamond?

New Scientist : Researchers at Swinburne University of Technology in Melbourne, Australia, have detected a pulsar with an orbiting object that may be composed of diamond. Using the CSIRO Parkes radio telescope in New South Wales, Matthew Bailes and coworkers detected the pulsar in December 2009. From follow-up observations taken with the Lovell radio telescope in the UK, they surmise that the orbiting object has a mass comparable to Jupiter’s but less than half its width. The extremely fast rotation of the pulsar and the size and density of the companion object led the researchers to conclude that the object is all that’s left of a star whittled down by the pulsar. Because the core of a stripped-down star would be mostly carbon, and because it would be under high pressure due to its own gravity, they believe the carbon would crystallize—most likely into diamond, much as carbon does deep inside Earth. The researchers published their results yesterday in Science.