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Marque J.,EGO European Gravitational Observatory
Proceedings of the International School of Physics "Enrico Fermi" | Year: 2010

Gravitational waves were predicted in 1916 by Einstein as a conse- quence of the theory of General Relativity: accelerated masses can produce ripples propagating at the speed of light, which perturb the space-time metric. Thanks to the extremely weak coupling with matter, gravitational waves can cross the universe undisturbed and, hence, are a probe of the regions where they are produced which is not accessible by the eventual electromagnetic counterpart. The gravitational waves sources of detectable amplitudes are expected to be compact astrophysical sources such as the coalescence of binaries formed by black holes and neutron stars, the collapses of stellar cores, or the rotation of non-axis-symmetric neutron stars. For more than 40 years the search for gravitational waves has been pursued with resonant detectors made of metallic bars. The development of gravitational wave detectors based on laser interferometers started in the early seventies. After more than two decades of development, the construction of the first interferometers with kilometer scale arms started in the nineties. The sensitivity of such detectors is fun- damentally proportional to its length, and with its 3 kilometer long arms Virgo is the largest gravitational wave detector in Europe, and the third largest in the world. It is located at the European Gravitational Observatory (EGO), close to Pisa, and it is designed to detect gravitational waves emitted by astrophysical sources in the frequency range between 10Hz and a few kHz. Among the other current ground- based gravitational wave detectors, Virgo is the one having the best sensitivity at low frequency, thanks to the particular seismic attenuators, from which the mirrors are suspended. Construction started in 1996 and ended in July 2003. After a very intense commissioning phase, the performances of the detector are now very close to the design ones, and the detector is entering the operation phase. In parallel, the design phase of the second generation of interferometers should be finalized this year with a construction planned to start in 2011. Also, the conceptual design is under study for a third generation. The corresponding European project is called the "Einstein Telescope". ©2010 by Società Italiana di Fisica.

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