Astronomers have spotted an exotic planet racing around a tiny star in our galactic backyard – and it seems to be made of diamond.
"The evolutionary history and amazing density of the planet all suggest it is comprised of carbon – i.e. a massive diamond orbiting a neutron star every two hours in an orbit so tight it would fit inside our own Sun," said Matthew Bailes of Swinburne University of Technology in Melbourne.
The planet is about 4000 light years away, or around an eighth of the way toward the center of the Milky Way from the Earth, and 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 tiny, dead neutron stars that are only around 20 kilometers (12.4 miles) in diameter and spin hundreds of times a second, emitting beams of radiation.
In the case of the latest pulsar, J1719-1438, the beams regularly sweep the Earth and have been monitored by telescopes in Australia, Britain and Hawaii, allowing astronomers to detect modulations due to the gravitational
pull of its unseen companion planet.
The measurements suggest the planet, which orbits its star every two hours and 10 minutes, has slightly more mass than Jupiter but is 20 times as dense, Bailes and colleagues reported in the journal Science on Thursday.
In addition to carbon, the new planet is also likely to contain oxygen, which may be more prevalent at the surface and is probably increasingly rare toward the carbon-rich center.
Its high density suggests the lighter elements of hydrogen and helium, which are the main constituents of gas giants like Jupiter, are not present.