Observatory of gravitational waves

In Astronomy, a observatory of gravitational waves (one also speaks about gravitational wave detector ) is a system intended to detect and measure the gravitational waves, predicted by the theory of the General relativity.

The observation of such waves could lead to a better knowledge of the black holes, which are differently invisible thus impossible to observe directly. In addition, these data have a theoretical importance, since they make it possible to test the theory of relativity.

A means relatively simple to observe these waves is known under the name of Barre of Weber: under the effect of a gravitational wave, the Espace-temps becomes deformed very slightly. Thus, an object is also deformed - one can then deduce the intensity and the source from the wave. There exists however of great practical limits to such devices of detection: the gravitational waves are of a tiny intensity, thus have only very little effect on the matter. Indeed, the Amplitude of such a wave decreases with the distance (is to be precise a reduction in $1/r$ ). Thus, even the most violent waves, like those produced within a binary black hole crumbling on itself, are reduced along their course in space to the Earth. Thus, one expects to detect signals of amplitude about $10^ {- 20}$ IF. For an object of 1 m length, that is equivalent to a movement such as its ends move $10^ {- 20}$ m one compared to the other. This distance is about one millionth of the width of a Atome.

Modern technologies use the Interférométrie Laser. Among the most powerful detectors, one counts: LIGO, VIRGO, GEO600, and TAMA. All these observatories are limited of resolution by the Bruit, which is a generic term to indicate all the disturbances external with measurement itself. The independent source of noise comes from measurement itself: that it is by laser where by measurement on a bar of Weber, uncertainties dependant on measurement and its method limit the precision of those. An important source of noise is the seismic noise, related to the vibrations of the Ground. Telescope S in orbit, still with the state of projects, such as LISA, would be insensitive to this disturbance. On the other hand, they would undergo other sources of noise, like the cosmic rays and the Solar wind.

Lastly, there exist other proposals like the MiniGRAIL, an antenna with spherical gravitational waves, Université of Leyde, with the Netherlands. Certain scientists also propose to observe the the Moon which, following the example bar of Weber, would become deformed under the effect of a gravitational wave.

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