Australian astronomers on Friday said they have spotted an exotic planet that is believed to be made of diamond in our galactic backyard. The sparkling world 4,000 light years away is 60,000 kilometers in diameter, five times that of the Earth, and is thought to be all that remains of a once-massive star which collapsed and was crunched down into crystalline. An international team lead by Matthew Bailes, from Swinburne University of Technology in Melbourne, said they have discovered a low-mass but dense object in orbit around a rapidly-rotating neutron star. He said the new planet is far denser than any other known so far and consists largely of carbon. Because it is so dense, scientists are certain that the carbon must be crystalline, so that a large part of the star is similar to a diamond. \"We have never seen anything like this before,\" Bailes told ABC Science on Friday. \"Producing such exotic planets is the exception rather than the rule, and requires special circumstances.\" Bailes said the new planet is probably the remnant of a once- massive star that has lost its outer layers to the so-called pulsar star it orbits. Pulsars are rotating stars with a diameter of about 20 kilometers which emit a beam of electromagnetic radiation. The findings are reported in the journal Science.