October 31, 2013
Former Missile Tracking Telescope Tracks Evolution Of Crab Pulsar
Lee Rannals for redOrbit.com – Your Universe Online
A former missile tracking telescope has helped astronomers determine how the magnetic field structure and rotation of a young and rapidly rotating Crab pulsar evolves.
Scientists wrote in the journal Science about a 22-year experiment that involved observing a steady change in the flashes of the Crab pulsar. This highly-compact star emits beams of radio waves that produce flashes each time it rotates, which occurs about 30 times a second.
The astronomer’s study helped inform them about the neutron star’s magnetic field, deepening the understanding about the otherwise inaccessible interior of the star. The new observations show how the spacing of flashes is increasing by 0.6 degrees per century, which means the magnetic pole is moving towards the equator.
The team used a 42-foot telescope that was formerly used to help track Blue Stream missiles at the Woomera Rocket Test Range in Australia until 1981. The telescope was eventually dismantled and transported to the Jodrell Bank Observatory in Cheshire, England.
Scientists have used the former missile-tracking telescope to observe the Crab pulsar for almost 31 years, during which time it has rotated about 30 billion times. Every time the neutron star has rotated during that time, Jodrell Bank has kept count of the rotation.
The most accurate observations ever made showed the small gradual change in the pulse spacing. Researchers said the most surprising aspect is this change is happening so rapidly. The team said the interior of the star is superconducting, and the magnetic field should be frozen in position at this point.
"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 Professor Sir Francis Graham Smith said in a press release.
Dr. Christine Jordan, who helps keep the telescope and observations running at Jodrell Bank, said it is amazing to think this relatively small missile-tracking telescope has proven to be such a big help to astronomers. She added that this is a “real sword to ploughshare concept in action.”
The team believes the study will have some important implications for scientific understanding of the evolution of pulsars and why they emit their flashes.
"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,” Dr. Patrick Weltevrede, also of The University of Manchester, said in the press release.