Planet-Forming Disk Spotted Around Dead Star

April 5, 2006

A disk of potentially planet-forming debris has been found around a pulsar about 13,000 light-years from Earth, scientists announced today.

The debris is most likely material that has fallen back toward the star after a supernova, or star explosion. The material could clump together to form planets, astronomers say, but such planets would be unlikely to harbor life.

"This disk looks remarkably like those also seen around ordinary young stars in which planets are known to form," said Deepto Chakrabarty, a physics professor at the Massachusetts Institute of Technology in Cambridge, who led the discovery team.

"But for the first time we may be seeing the start of planet formation in the very different, harsh environment that exists around an old dead star like a pulsar," he added.

Pulsars form during the collapse and death of stars that are between 10 and 20 times more massive than our sun, Chakrabarty explains.

Chakrabarty described the discovery in a press teleconference this afternoon. A paper detailing the debris disk will appear in tomorrow's issue of the journal Nature.

Pulsar Planets

When a massive star collapses, the inner core, which is about 10 percent of the original mass, is compressed into a dense object only 10 miles (16 kilometers) across called a neutron star.

The other 90 percent of the mass is ripped away in an explosion.

Neutron stars that rotate rapidly give off regular pulses of radiation, which is why they are called pulsars, Chakrabarty said.

Scientists theorized that some of the ejected material could have falled back toward the pulsar and stabilized in a disk around the star.

Using NASA's Spitzer Space Telescope, Chakrabarty and his colleagues found one of these fallback disks around a pulsar named 4U 0142+61 in the constellation Cassiopeia.

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