New 'fix' for cosmic clocks could help uncover ripples in space-time

An international team of scientists have developed a promising new technique which could turn pulsars -- superb natural cosmic clocks -- into even more accurate time-keepers.

This important advance, led by scientists at The University of Manchester and appearing June 24 in the journal Science Express, could improve the search for gravitational waves and help studies into the origins of the universe.

The direct discovery of gravitational waves, which pass over cosmic clocks and cause them to change, could allow scientists to study violent events such as the merging of super-massive black holes and help understand the universe shortly after its formation in the Big Bang.

The scientists made their breakthrough using decades-long observations from the 76-m Lovell radio telescope at The University of Manchester's Jodrell Bank Observatory to track the radio signals of extreme stars known as pulsars.

Pulsars are spinning collapsed stars which have been studied in great detail since their discovery in 1967. The extremely stable rotation of these cosmic fly-wheels has previously led to the discovery of the first planets orbiting other stars and provided stringent tests for theories of gravity that shape the Universe.

However, this rotational stability is not perfect and, until now, slight irregularities in their spin have significantly reduced their usefulness as precision tools.

The team, led by the University of Manchester's Professor Andrew Lyne, has used observations from the Lovell telescope to explain these variations and to demonstrate a method by which they may be corrected.

Professor Lyne explains: "Mankind's best clocks all need corrections, perhaps for the effects of changing temperature, atmospheric pressure, humidity or local magnetic field. Here, we have found a potential means of correcting an astrophysical clock."

The rate at which all pulsars spin is known to be decreasing very slowly. What the team has found is that the deviations arise because there are actually two spin-down rates and not one, and that the pulsar switches between them, abruptly and rather unpredictably.

These changes are associated with a change in the shape of the pulse, or tick, emitted by the pulsar. Because of this, precision measurements of the pulse shape at any particular time indicate exactly what the slowdown rate is and allow the calculation of a "correction." This significantly improves their properties as clocks.

The results give a completely new insight into the extreme conditions near neutron stars and also offer the potential for improving already very precise experiments in gravitation.

It is hoped that this new understanding of pulsar spin-down will improve the chances that the fastest spinning pulsars will be used to make the first direct detection of ripples, known as gravitational waves, in the fabric of space-time. ...

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