Astronomers Unlock Mysteries Surrounding Crab Pulsar

Using a radio telescope once used to track ballistic missiles, astronomers have unlocked several mysteries surrounding the rapidly rotating Crab pulsar.

Formed nearly 1,000 years ago in an explosion bright enough to be seen during the daytime from both Europe and China, the Crab pulsar is a neutron star with the mass of nearly 1 million Earths, all stuffed inside a body only about 25 kilometers across. The immensely dense object rotates at the dizzying speed of 30 rotations per second, emitting beams of radio waves every time it rotates -- hence the term "pulsar."

A 22-year experiment led by researchers from the University of Manchester found the spacing between the pulses, which come in pairs, is increasing by 0.6 degrees per century, meaning the magnetic pole is migrating toward the equator.

According to the researchers, the rate of change was surprising given the interior of the star is superconducting and the magnetic field should be frozen in place.

"This pulsar is just 960 years old, so while 22 years gives only a small sample of its lifetime, it is a much larger fraction of a stellar lifetime than astronomers usually get to study," co-author Francis Graham Smith said in a statement.

The 42-foot telescope used to track the Crab pulsar -- a feat it's undertaken daily for 31 years now -- was formerly used to track the Blue Streak missile at the Woomera Rocket Test Range in Australia until 1981, at which point it was dismantled and reconstructed at the Jodrell Bank Observatory in England.

"It is amazing to think that this relatively small missile-tracking telescope, installed in Australia in 1974 by Marconi and donated to the Jodrell Bank Observatory in 1981 where it was converted to observe pulsars, has proved to be such a boon to astronomers," said Christine Jordan, who ensures that the telescope and observations at Jodrell Bank are always running. "This is a real sword to ploughshare concept in action."

According to Patrick Weltevrede, a University of Manchester researcher, the results of the latest study could have key implications for understanding not just the Crab pulsar, but others like it.

"The Crab pulsar is iconic; it is seen across the entire electromagnetic spectrum and is an exemplar and so this result provides vital clues about how these cosmic lighthouses shine and explaining a long-standing mystery about the way pulsars slow down over time," he said.