24 Aralık 2007 Pazartesi
LIGO and EGO
Laser Interferometer Gravitational-Wave Observatory
LIGO stands for Laser Interferometer Gravitational-Wave Observatory. Cofounded in 1992 by Kip Thorne and Ronald Drever of Caltech and Rainer Weiss of MIT, LIGO is a joint project between scientists at MIT and Caltech. It is sponsored by the National Science Foundation (NSF). At the cost of $365 million (in 2002 USD), it was the largest and most ambitious project ever funded by NSF (and still is as of 2007). The international LIGO Scientific Collaboration (LSC) is a growing group of researchers, some 400 individuals at roughly 40 institutions, working to analyze the data from LIGO and other detectors, and working toward more sensitive future detectors.
LIGO's mission is to directly observe gravitational waves of cosmic origin. These waves were first predicted by Einstein's Theory of General Relativity in 1916, when the technology necessary for their detection did not yet exist. Gravitational waves were indirectly confirmed to exist when observations were made of the binary pulsar PSR 1913+16, for which the Nobel Prize was awarded to Hulse and Taylor in 1993.
Direct detection of gravitational waves has long been sought, for it would open up a new branch of astronomy to complement electromagnetic telescopes and neutrino observatories. Joseph Weber pioneered the effort to detect gravitational waves in the 1960s through his work on resonant mass bar detectors.Bar detectors continue to be used at six sites worldwide. By the 1970s, scientists including Rainer Weiss realized the applicability of laser interferometry to gravitational wave measurements.
In August 2002, LIGO began its search for cosmic gravitational waves. Emissions of gravitational waves are expected from binary systems (collisions and coalescences of neutron stars or black holes), supernova of massive stars (which form neutron stars and black holes), rotations of neutron stars with deformed crusts, and the remnants of gravitational radiation created by the birth of the universe. The observatory may in theory also observe more exotic currently hypothetical phenomena, such as gravitational waves caused by oscillating cosmic strings or colliding domain walls. Since the early 1990s, physicists have believed that technology is at the point where detection of gravitational waves—of significant astrophysical interest—is possible.
The European Gravitational Observatory
The European Gravitational Observatory or EGO is located in the countryside near Pisa in the Commune of Cascina. In order to ensure the long term scientific exploitation of the VIRGO interferometric antenna for gravitational waves detection as well as to foster European collaboration in this upcoming field, the VIRGO funding institutions (CNRS for France and INFN for Italy) have created a consortium called EGO (European Gravitational Observatory).
VIRGO is a 3 kilometer interferometer built through a French-Italian collaboration. This collaboration involves 11 laboratories in France and Italy and more than 150 scientists.
EGO is established under the Italian law. Its governing body is the Council composed of six members nominated by the funding institutions. The Council appoints a Director who is the legal representative and chief executive of EGO. The Scientific and Technical Advisory Committee advises the Council on scientific and technical activities carried out by the Consortium. It is composed of up to ten scientific personalities.