spacetoday.net: Gravitational waves may set speed limit for spinning pulsars

Posted: Thu, Jul 3, 2003, 11:29 AM ET (1529 GMT)
Pulsar and companion star illustration (NASA/GSFC)

Astronomers reported Wednesday that gravitational waves may prevent pulsars from spinning too fast and destroying themselves. The researchers, in an article published in Thursday's issue of the journal Nature, reached this conclusion through the study of pulsars observed by NASA's Rossi X-Ray Timing Explorer spacecraft. Although the spacecraft is capable of detecting pulsars spinning as fast as 4,000 times a second, astronomers have yet to find a pulsar spinning more than 619 revolutions per second, well below the limit of 1,000 to 3,000 revolutions per second at which the pulsar would break apart. Astronomers believe that gravitational waves, distortions in time and space predicted by Einstein, provide a feedback effect that prevents pulsars from spinning too fast: as pulsars spin up, usually by accreting matter from a companion star, the amount of gravitational radiation they emit also increases to the point where the gravitational waves balance the added angular momentum from the accreted matter, stopping the star from spinning any faster. Astronomers hope to eventually be able to test this model by detecting gravitational waves directly through the new Laser Interferometer Gravitational-Wave Observatory (LIGO).