The Virgo interferometer in Santo Stefano a Macerata, near Pisa, is a large interferometer designed to detect gravitational waves predicted by Einstein’s general theory of relativity, and isolated from external disturbances: its mirrors and instrumentation are suspended and its laser beam operates in a vacuum. The instrument has two arms, 3 km long.
Virgo is part of a scientific collaboration of laboratories from Italy and France, the Netherlands, Poland, Hungary and Spain. Other interferometers similar to Virgo have the same goal of detecting gravitational waves, including the two LIGO interferometers in the United States (at the Hanford Site and in Livingston, Louisiana).
Since 2007, Virgo and LIGO have agreed to share and jointly analyze the data recorded by their detectors and to jointly publish their results.
The interferometer is named for the Virgo Cluster of about 1,500 galaxies in the Virgo constellation, about 50 million light-years from Earth. As no terrestrial source of gravitational wave is powerful enough to produce a detectable signal, Virgo must observe the Universe. The more sensitive the detector, the further it can see gravitational waves, which then increases the number of potential sources. Virgo is potentially sensitive to neutron stars or black holes; supernova explosions.