From: LARRY KLAES (ljk4_at_msn.com)
Date: Fri Dec 05 2003 - 06:54:09 PST
Press Release 2003/03 - 3rd December 2003
Pulsar find boosts hope for gravity-wave hunters
Neutron star pairs may merge and give off a burst of gravity waves about six times more often than previously thought, scientists report in today's issue of the journal Nature [ 4th December 2003]. If so, the current generation of gravity-wave detectors might be able to register such an event every year or two, rather than about once a decade - the most optimistic prediction until now. This means that the direct detection of gravity waves - a key prediction made by Albert Einstein's general theory of relativity - might be closer than previously suspected. Astronomers have indirect evidence of their existence but have yet to detect them directly.
Until now, it was thought that such neutron star mergers were comparatively rare, about one every few decades, but the discovery of the new binary system by an international team of scientists from Italy, Australia, the UK and the USA using the 64-m Parkes radio telescope in New South Wales has enabled the estimate of such an occurrences to be greatly increased.
As team member Dr Dick Manchester of CSIRO pointed out, "It is now thought that they might occur at least six or seven times more often." Professor Andrew Lyne, Director of the University of Manchester's Jodrell Bank Observatory, added, "this discovery is good news for gravity-wave astronomers; it may be possible to study one of these cosmic catastrophes every few years, instead of having to wait half a career."
Both objects in orbit around each other are "neutron" stars, city-sized balls of a super-dense form of matter - the remnants of supernovae, the cataclysmic explosions that mark the death of giant stars. One of the neutron stars is a pulsar, PSR J0730-3039. It is spinning round 45 times per second emitting rotating beams of radio waves which were detected as regular pulses of energy at the Parkes Telescope. Detailed timing analysis of these pulses allowed the extreme characteristics of the neutron star's orbit to be determined.
Though separated by more than twice the distance of the Moon from the Earth, their large masses, each somewhat more than our Sun, mean that they orbit each other in just over 2 hours. As a result, they are already losing energy by radiating gravitational waves - but currently at too low a level to be detected directly. This is causing a "dance of death" during which the two stars slowly spiral in towards each other. They will finally fuse - perhaps forming a black hole - in about 85 million years resulting in a burst of gravity wave rippling out across the galaxy at the speed of light. As Professor Nicolo D'Amico, Director of the Cagliari Astronomical Observatory in Sardinia, stated, "if this were to happen now, it could be detected by the current generation of gravitational wave detectors such as LIGO-I, VIRGO or GEO."
The importance of this discovery is that it implies that these events are likely to occur much more frequently than thought before. "We now expect that the current gravitational wave detectors could register a neutron star merger every one or two years" said Dr Vicky Kalogera, Assistant Professor of Physics and Astronomy at Northwestern University in Illinois, USA, who with colleagues Chunglee Kim and Duncan Lorimer have modelled the coalescence rates to provide the new estimates. "It does look now as though it may not be too long before we will have the exciting prospect of the first direct detection of gravitational waves."
This new system is more extreme than any previously discovered and, because it contains a pulsar, it forms a superb test-bed for testing Einstein's predictions. Pulsars are incredibly accurate clocks and this property will enable us to understand gravity under extreme conditions. Gravity is one of the fundamental forces of the Universe and determines the evolution and structure of the Universe as we see it today.
For the rest of the article, go here:
http://www.jb.man.ac.uk/news/binary/
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