Gravitational waves are produced when matter is accelerated in
an asymmetrical way; but due to the nature of the gravitational
interaction, detectable levels of radiation are produced only
when very large masses are accelerated in very strong
gravitational fields. Such a situation cannot be found on earth
but is found in a variety of astrophysical systems. Gravitational
wave signals are expected over a wide range of frequencies; from
Hz in the case of ripples in the cosmological background
to
Hz from the formation of neutron stars in supernova
explosions. The most predictable sources are binary star systems.
However there are many sources of much greater astrophysical
interest associated with black hole interactions and
coalescences, neutron star coalescences, low-mass X-ray binaries
such as Sco-X1, stellar collapses to neutron stars and black
holes (supernova explosions), pulsars, and the physics of the
early Universe. For a full discussion of sources refer to the
material contained in references [55
,
24,
69].
Why is there currently such interest worldwide in the detection of gravitational waves? Partly because observation of the velocity and polarisation states of the signals will allow a direct experimental check of the wave predictions of General Relativity; but more importantly because the detection of the signals should provide observers with new and unique information about astrophysical processes. It is interesting to note that the gravitational wave signal from a coalescing compact binary star system has a relatively simple form and the distance to the source can be obtained from a combination of its signal strength and its evolution in time. If the redshift at that distance is found, Hubble's Constant - the value for which has been a source of lively debate for many years - may then be determined with, potentially, a high degree of accuracy [90].
Only now technology has reached a stage where the building of detectors of the sensitivity required to observe such interesting sources can be envisaged.
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Gravitational Wave Detection by Interferometry (Ground
and Space)
Sheila Rowan and Jim Hough http://www.livingreviews.org/lrr-2000-3 © Max-Planck-Gesellschaft. ISSN 1433-8351 Problems/Comments to livrev@aei-potsdam.mpg.de |