History & Purpose
History
In the 1970's, two European groups initiated investigations into laser-interferometric gravitational wave (GW) detection. In 1975 the Max Planck Institute for Astrophysics in Munich started with a prototype of 3 m armlength, which later (1983), at the Max Planck Institute of Quantum Optics (MPQ) in Garching, led to a prototype with 30 m armlength. In 1977 the Department of Physics and Astronomy of the University of Glasgow began similar investigations, and in 1980 started operation of a 10 m prototype. In 1985 the Garching group proposed the construction of a large detector with 3 km armlength, the British group an equivalent project in 1986. The two groups combined their efforts in 1989 - the project GEO was born, with the Harz mountains (Northern Germany) considered an ideal site. The project was, however, not funded, because of financial problems. Thus in 1994 a smaller detector was proposed: GEO600, to be built in the lowlands near Hannover, with arms of 600 m in length. The construction of this British-German GW detector started in September 1995. In 2001 the Max Planck Institute for Gravitational Physics (Albert Einstein Institute, AEI) in Potsdam took over the Hannover branch of the MPQ, and since 2002 the detector is operated by a joint Center of Gravitational Physics of AEI and Leibniz Universität Hannover, together with the universities of Glasgow and Cardiff. Since 2002 GEO600 participated in several data runs in coincidence with the LIGO detectors. In 2006, GEO600 has reached the design sensitivity, but up to now no signal has been detected. The next aim is to reduce the remaining noise by another factor of about 10, until 2014.
Worldwide Network
Reliable detection of gravitational waves requires the operation of at least two detectors in coincidence – if the signals coincide with those of a distant detector, local perturbations can be ruled out. In order to obtain the full information about the gravitational waves (source position, polarization), data from at least four detectors have to be compared. Thus, the GEO600 team collaborates with the GW groups in the USA (LIGO), in France/Italy (Virgo) and in Japan (TAMA300). As a member of the LIGO Scientific Collaboration (LSC) and the Virgo Collaboration, GEO600 has performed several long-term data runs together with the other gravitational wave detectors.
Aims
Gravitational wave astronomy provides a totally new look at the Universe. Gravitational waves give information on supernovae, black holes, pulsars, compact binaries and the cosmic background radiation that cannot be obtained by other means. Furthermore, observation of binary systems allows to determine absolute distances and thus an accurate value of the Hubble constant.
Funding
Financial support of the GEO project has been supplied by the State of Lower Saxony, the Max Planck Society, the Science and Technology Facilities Council STFC (UK), the Volkswagen Foundation, and the Federal Republic of Germany. Personnel costs are supplied by the Max Planck Society and the Leibniz University Hannover, running costs by the Max Planck Society.
