ired, the whole interferometer attains optical perfection and is extremely well isolated from the rest of the world in order to be only sensitive to the gravitational waves. To achieve it, Italian and French scientists involved in the project, have developed most advanced techniques in the field of high power ultrastable lasers, high reflectivity mirrors, seismic isolation and position and alignment control.

In the field of optics, Virgo uses a new generation of ultrastable lasers, and the most stable oscillator ever built. A specific optical coating facility has been built to produce extremely high quality mirrors combining the highest reflectivity (over 99,999 %), with nanometer surface control

To avoid spurious motions of the optical components due to seismic noise; each one of them is isolated by a 10m high, very elaborate system of compound pendulums. Because the presence of a residual gas would slightly perturb the measurements the light beam must propagate under ultra high vacuum. The two tubes, 3km long and 1.2m diameter

On May 18, 2007, the Virgo interferometer began its first scientific production run. It is about a crucial stage in the tracking with the gravitational waves. Virgo, the largest European detector (Franco-Italian), comes to join detectors LIGO, in the United States. This ultraperformant network of instruments of observation will have in particular the capacity to observe the coalescence (1) of binary black holes in distant galaxies and to provide information on the direction of the source. The operation of Virgo is jointly assured by CNRS and the national Institute Italian nuclear physics (INFN).

The gravitational waves, predicted by the general theory of relativity, are deformations of space time. They are produced by astrophysical phenomena violent one in our galaxy and well beyond. For example, explosions of supernovas or the coalescence of two compact bodies, such holes black or neutron stars. Today, only of the indirect evidences of the emission of gravitational waves were observed (rewarded by the Nobel Prize for physics in 1993).

The first direct observation will open the field of gravitational astronomy and will make it possible to look further into our comprehension of the gravitation and general relativity. With the first scientific & engineering production run of Virgo, which began on May 18, 2007, it is from now on possible thing. Virgo functions of day like night, constantly with the listening of the gravitational signals coming from the close Universe (to the galaxy cluster Virgo, from where its name).

A team of operators and scientists exploit and monitor the instrument 24 hours a day and 7 days a week. The signals are detected, recorded and are the subject of a first analysis using an information processing system on line. These data are then availability of the scientific community for a more advanced later study. The gravitational wave detector Virgo is primarily a laser interferometer of Michelson made up of two three kilometers length orthogonal arms. The light travels several times between two mirrors located at the ends of each arm, before combining with the light coming from the other arm to interfere.

The gravitational waves should appear by dilations and contractions of the distance between the mirrors of each arm (and by a change of the interference), about a billionth of the diameter of an atom (10-18 meter). To detect so negligible changes, the detector calls upon the most advanced technologies, in the fields of the metallurgy, optics, the systems of control, the vacuum, data processing, the analysis of data etc the laboratories of CNRS of Annecy, Lyon, Nice, Orsay and Paris (2) is strongly implied in Virgo and the consortium EGO (cofinanced by CNRS and the INFN), which shelters and ensures the operation of Virgo. The teams of VIRGO are allied to the scientists of LIGO in the United States and GEO in the United Kingdom and in Germany, in order to seek the gravitational waves jointly. The combined data will increase the chances to find the first waves gravitational and will provide more technology information on the position of the source. The common analysis of the data will be made as if they came from a single detectormade up of several probes distributed on two banks of the Atlantic and the East coast of the Pacific.

About VIRGO-
The Virgo detector for gravitational waves consists mainly in a Michelson laser interferometer made of two orthogonal arms being each 3 kilometers long. Multiple reflections between mirrors located at the extremities of each arm extend the effective optical length of each arm up to 120 kilometers. Virgo is located within the site of EGO, European Gravitational Observatory, based at Cascina, near Pisa on the river Arno plain.

The frequency range of Virgo extends from 10 to 6,000 Hz. This range as well as the very high sensitivity should allow detection of gravitational radiation produced by supernovae and coalescence of binary systems in the milky way and in outer galaxies, for instance from the Virgo cluster.

In order to reach the extreme sensitivity required, the whole interferometer attains optical perfection and is extremely well isolated from the rest of the world in order to be only sensitive to the gravitational waves. To achieve it, Italian and French scientists involved in the project, have developed most advanced techniques in the field of high power ultrastable lasers, high reflectivity mirrors, seismic isolation and position and alignment control.

In the field of optics, Virgo uses a new generation of ultrastable lasers, and the most stable oscillator ever built. A specific optical coating facility has been built to produce extremely high quality mirrors combining the highest reflectivity (over 99,999 %), with nanometer surface control

To avoid spurious motions of the optical components due to seismic noise; each one of them is isolated by a 10m high, very elaborate system of compound pendulums. Because the presence of a residual gas would slightly perturb the measurements the light beam must propagate under ultra high vacuum. The two tubes, 3km long and 1.2m diameter e

The first direct observation will open the field of gravitational astronomy and will make it possible to look further into our comprehension of the gravitation and general relativity. With the first scientific & engineering production run of Virgo, which began on May 18, 2007, it is from now on possible thing. Virgo functions of day like night, constantly with the listening of the gravitational signals coming from the close Universe (to the galaxy cluster Virgo, from where its name).

A team of operators and scientists exploit and monitor the instrument 24 hours a day and 7 days a week. The signals are detected, recorded and are the subject of a first analysis using an information processing system on line. These data are then availability of the scientific community for a more advanced later study. The gravitational wave detector Virgo is primarily a laser interferometer of Michelson made up of two three kilometers length orthogonal arms. The light travels several times between two mirrors located at the ends of each arm, before combining with the light coming from the other arm to interfere.

The gravitational waves should appear by dilations and contractions of the distance between the mirrors of each arm (and by a change of the interference), about a billionth of the diameter of an atom (10-18 meter). To detect so negligible changes, the detector calls upon the most advanced technologies, in the fields of the metallurgy, optics, the systems of control, the vacuum, data processing, the analysis of data etc the laboratories of CNRS of Annecy, Lyon, Nice, Orsay and Paris (2) is strongly implied in Virgo and the consortium EGO (cofinanced by CNRS and the INFN), which shelters and ensures the operation of Virgo. The teams of VIRGO are allied to the scientists of LIGO in the United States and GEO in the United Kingdom and in Germany, in order to seek the gravitational waves jointly. The combined data will increase the chances to find the first waves gravitational and will provide more technology information on the position of the source. The common analysis of the data will be made as if they came from a single detectormade up of several probes distributed on two banks of the Atlantic and the East coast of the Pacific.

About VIRGO-
The Virgo detector for gravitational waves consists mainly in a Michelson laser interferometer made of two orthogonal arms being each 3 kilometers long. Multiple reflections between mirrors located at the extremities of each arm extend the effective optical length of each arm up to 120 kilometers. Virgo is located within the site of EGO, European Gravitational Observatory, based at Cascina, near Pisa on the river Arno plain.

The frequency range of Virgo extends from 10 to 6,000 Hz. This range as well as the very high sensitivity should allow detection of gravitational radiation produced by supernovae and coalescence of binary systems in the milky way and in outer galaxies, for instance from the Virgo cluster.

In order to reach the extreme sensitivity required, the whole interferometer attains optical perfection and is extremely well isolated from the rest of the world in order to be only sensitive to the gravitational waves. To achieve it, Italian and French scientists involved in the project, have developed most advanced techniques in the field of high power ultrastable lasers, high reflectivity mirrors, seismic isolation and position and alignment control.

In the field of optics, Virgo uses a new generation of ultrastable lasers, and the most stable oscillator ever built. A specific optical coating facility has been built to produce extremely high quality mirrors combining the highest reflectivity (over 99,999 %), with nanometer surface control

To avoid spurious motions of the optical components due to seismic noise; each one of them is isolated by a 10m high, very elaborate system of compound pendulums. Because the presence of a residual gas would slightly perturb the measurements the light beam must propagate under ultra high vacuum. The two tubes, 3km long and 1.2m diameter

combining with the light coming from the other arm to interfere.

The gravitational waves should appear by dilations and contractions of the distance between the mirrors of each arm (and by a change of the interference), about a billionth of the diameter of an atom (10-18 meter). To detect so negligible changes, the detector calls upon the most advanced technologies, in the fields of the metallurgy, optics, the systems of control, the vacuum, data processing, the analysis of data etc the laboratories of CNRS of Annecy, Lyon, Nice, Orsay and Paris (2) is strongly implied in Virgo and the consortium EGO (cofinanced by CNRS and the INFN), which shelters and ensures the operation of Virgo. The teams of VIRGO are allied to the scientists of LIGO in the United States and GEO in the United Kingdom and in Germany, in order to seek the gravitational waves jointly. The combined data will increase the chances to find the first waves gravitational and will provide more technology information on the position of the source. The common analysis of the data will be made as if they came from a single detectormade up of several probes distributed on two banks of the Atlantic and the East coast of the Pacific.

About VIRGO-
The Virgo detector for gravitational waves consists mainly in a Michelson laser interferometer made of two orthogonal arms being each 3 kilometers long. Multiple reflections between mirrors located at the extremities of each arm extend the effective optical length of each arm up to 120 kilometers. Virgo is located within the site of EGO, European Gravitational Observatory, based at Cascina, near Pisa on the river Arno plain.

The frequency range of Virgo extends from 10 to 6,000 Hz. This range as well as the very high sensitivity should allow detection of gravitational radiation produced by supernovae and coalescence of binary systems in the milky way and in outer galaxies, for instance from the Virgo cluster.

In order to reach the extreme sensitivity required, the whole interferometer attains optical perfection and is extremely well isolated from the rest of the world in order to be only sensitive to the gravitational waves. To achieve it, Italian and French scientists involved in the project, have developed most advanced techniques in the field of high power ultrastable lasers, high reflectivity mirrors, seismic isolation and position and alignment control.

In the field of optics, Virgo uses a new generation of ultrastable lasers, and the most stable oscillator ever built. A specific optical coating facility has been built to produce extremely high quality mirrors combining the highest reflectivity (over 99,999 %), with nanometer surface control

To avoid spurious motions of the optical components due to seismic noise; each one of them is isolated by a 10m high, very elaborate system of compound pendulums. Because the presence of a residual gas would slightly perturb the measurements the light beam must propagate under ultra high vacuum. The two tubes, 3km long and 1.2m diameter

osition of the source. The common analysis of the data will be made as if they came from a single detectormade up of several probes distributed on two banks of the Atlantic and the East coast of the Pacific.

About VIRGO-
The Virgo detector for gravitational waves consists mainly in a Michelson laser interferometer made of two orthogonal arms being each 3 kilometers long. Multiple reflections between mirrors located at the extremities of each arm extend the effective optical length of each arm up to 120 kilometers. Virgo is located within the site of EGO, European Gravitational Observatory, based at Cascina, near Pisa on the river Arno plain.

The frequency range of Virgo extends from 10 to 6,000 Hz. This range as well as the very high sensitivity should allow detection of gravitational radiation produced by supernovae and coalescence of binary systems in the milky way and in outer galaxies, for instance from the Virgo cluster.

In order to reach the extreme sensitivity required, the whole interferometer attains optical perfection and is extremely well isolated from the rest of the world in order to be only sensitive to the gravitational waves. To achieve it, Italian and French scientists involved in the project, have developed most advanced techniques in the field of high power ultrastable lasers, high reflectivity mirrors, seismic isolation and position and alignment control.

In the field of optics, Virgo uses a new generation of ultrastable lasers, and the most stable oscillator ever built. A specific optical coating facility has been built to produce extremely high quality mirrors combining the highest reflectivity (over 99,999 %), with nanometer surface control

To avoid spurious motions of the optical components due to seismic noise; each one of them is isolated by a 10m high, very elaborate system of compound pendulums. Because the presence of a residual gas would slightly perturb the measurements the light beam must propagate under ultra high vacuum. The two tubes, 3km long and 1.2m diameter

ired, the whole interferometer attains optical perfection and is extremely well isolated from the rest of the world in order to be only sensitive to the gravitational waves. To achieve it, Italian and French scientists involved in the project, have developed most advanced techniques in the field of high power ultrastable lasers, high reflectivity mirrors, seismic isolation and position and alignment control.

In the field of optics, Virgo uses a new generation of ultrastable lasers, and the most stable oscillator ever built. A specific optical coating facility has been built to produce extremely high quality mirrors combining the highest reflectivity (over 99,999 %), with nanometer surface control

To avoid spurious motions of the optical components due to seismic noise; each one of them is isolated by a 10m high, very elaborate system of compound pendulums. Because the presence of a residual gas would slightly perturb the measurements the light beam must propagate under ultra high vacuum. The two tubes, 3km long and 1.2m diameter each are actually the largest ultra high vacuum vessels in Europe and the second largest in the world. The environment of the Virgo interferometer is quieter than that of a spacecraft orbiting the earth.

Virgo, the construction of which was completed in June 2003 and is at present is in the commissioning phase, will run day and night listening to all gravitational signals which may arrive at any time and coming from any part of the Universe. The signals are detected, recorded and pre-analysed through an on-line computing system. These data will then be made available to the scientific community for further analysis