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Pulsars give more accurate test of relativity

Pulsars give more accurate test of relativity

 
Double pulsar

Double vision: New, accurate measurements of a double pulsar system will allow researchers to test theories of general relativity more precisely than ever before, according to experts. Image shows an artist’s impression of the movement of the binary pair.

Credit: Swinburne University

BRISBANE: A new measurement of the universe’s only known double pulsar system will allow astrophysicists to test Einstein’s general theory of relativity more stringently than ever before.

Researchers at Swinburne University’s Centre for Astrophysics and Supercomputing in Melbourne, Australia, were able to accurately measure the distance from Earth to the two pulsars by designing a computer program that combines information from all of Australia’s major telescopes, effectively increasing their sensitivity.

Ideal testbed

The measurements revealed that the pulsars are much further away than previously thought, and in an ideal part of the universe for testing the theory of general relativity, according to a paper in the U.S. journal Science.

“It’s a very exciting gravitational laboratory,” said astrophysicist Matthew Bailes, one of paper’s authors.

The researchers used the improved sensitivity of the telescopes to measure the pulsars’ parallax, or the perceived ‘wobble’ of the star pair (actually caused by the Earth’s movement around the Sun) to determine accurately how far away the pulsars are.

With this information, astronomers can predict what changes should arise in the pulsars’ orbits according to Einstein’s theory. With this data in hand, an international team of astronomers has now begun a ten-year effort to map the stars’ orbits with “ridiculous precision”, Bailes said. “They’re getting closer by just millimetres per orbit.”

If the predictions match the results over the ten years, researchers will be 99.99 per cent certain that the General Theory of Relativity is correct, up from the current certainty of 99.95 per cent.

The gravity connection

General relativity was proposed by Albert Einstein in 1916 and is the currently-accepted theory of gravitation, but there are also several competing theories, so physicists are on the hunt for data that can verify or disprove Einstein’s theory.

According to Einstein’s theory, time and gravity are connected, so that time slows down close to an object with strong gravity.

The theory also proposes that gravity travels in gravitational waves, but these waves are so feeble that they can only be detected by measuring their effect on rare binary star systems that are not accelerating relative to Earth, like the double pulsar.

George Hobbs, an astronomer at CSIRO’s Australia Telescope National Facility, said that a large number of new and interesting tests of general relativity can now be carried out on the pulsars.

“A lot of the interesting relativistic effects rely on us knowing the distance to the pulsar,” Hobbs said. “The new paper provides a very accurate and precise distance.”

http://www.cosmosmagazine.com/news/2528/pulsars-give-even-more-accurate-test-relativit

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February 18, 2009 - Posted by | 1

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