Washington, June 3 : Scientists have ruled out gravitational waves as the reason behind the slowing down of a mysterious spinning neutron star known as the Crab Pulsar, a phenomenon known as "pulsar braking".
Pulsars are almost perfect shaped, tiny, extremely dense spheres made almost entirely of neutrons.
The Crab Pulsar is located in the Crab Nebula, one of the most famous objects in the sky. Astronomers have long known that the pulsar spins about 30 times per second, and that the rate is slowing.
The Crab Pulsar contains more mass than the sun, yet has a radius of only 10 kilometers, or about 6.2 miles.
Scientists have proposed a number of hypotheses for the physical mechanism behind the spin "braking," including such phenomena as asymmetric particle emission, magnetic dipole radiation and gravitational-wave emission.
Gravitational waves are ripples in the fabric of space and time predicted by Einstein's general theory of relativity but never observed.
But, researchers with the Laser Interferometer Gravitational Wave Observatory (LIGO) Scientific Collaboration - an international collaboration headed by a University of Florida physicist - have ruled out the emission of gravitational waves as the reason behind the "spin braking".
The hypothesis was that the spinning Crab Pulsar might generate gravitational waves as a result of even a tiny deformation of its shape. Such a deformation might result from physical strain on the pulsar's semi-solid crust, or its enormous magnetic field. esearchers at LIGO used the observatory's network of interferometers - essentially, extremely sensitive rangefinders that can detect extremely small motions indicative of gravitational waves - to test this hypothesis.
When the scientists analyzed data gathered from the Crab Nebula region, they found no evidence of gravitational waves, ruling it out as a cause for the Pulsar braking.
"The physics world has been waiting eagerly for scientific results from LIGO," said Joseph Taylor, an astronomer and professor of physics at Princeton University who won the Nobel Prize for indirect detection of gravitational waves.
"It is exciting that we now know something concrete about how nearly spherical a neutron star must be, and we have definite limits on the strength of its internal magnetic field," he added.