Virgo interferometer

The Virgo experiment
Formation1993
TypeInternational scientific collaboration
PurposeGravitational wave detection
HeadquartersEuropean Gravitational Observatory
Location
Coordinates43°37′53″N 10°30′16″E / 43.6313°N 10.5045°E / 43.6313; 10.5045
Region
Italy
FieldsBasic research
Spokesperson
Gianluca Gemme
AffiliationsLVK (LIGO-Virgo-KAGRA collaboration)
Budget
About ten million euros per year
Staff
Around 880 people participate in the Virgo Collaboration
Websitewww.virgo-gw.eu
For broader coverage of detectors like Virgo, see Ground-based interferometric gravitational-wave search.

The Virgo interferometer is a large-scale experiment for detecting gravitational waves. It is in Santo Stefano a Macerata, near the city of Pisa, Italy. The instrument –a Michelson interferometer – has two arms that are 3 kilometres (1.9 mi) long and contain its mirrors and instrumentation in an ultra-high vacuum.

Virgo is hosted by the European Gravitational Observatory (EGO), a consortium founded by the French Centre National de la Recherche Scientifique (CNRS) and the Italian Istituto Nazionale di Fisica Nucleare (INFN).[1] The Virgo Collaboration operates the detector, and defines the strategy and policy for its use and upgrades. The collaboration consists of more than 850 members in 16 countries.[2] The Virgo interferometer works in collaboration with other similar detectors, including the two LIGO interferometers in the United States (at the Hanford Site and in Livingston, Louisiana) and the Japanese interferometer KAGRA (in the Kamioka mine). Cooperation between several detectors is crucial for detecting gravitational waves and pinpointing their origin; the LIGO and Virgo collaborations have shared their data since 2007, and with KAGRA since 2019, to form the LIGO-Virgo-KAGRA (LVK) collaboration.[3]

The interferometer is named after the Virgo Cluster, a cluster of about 1,500 galaxies in the Virgo constellation about 50 million light-years from Earth.[4] It was conceived and built when gravitational waves were only a prediction of general relativity; the project was first approved in 1992 and the construction was completed in 2003. After several years of improvements without detection, it was shut down in 2011 for the "Advanced Virgo" upgrades. In 2015, the first observation of gravitational waves was made by the two LIGO detectors, while Virgo was still being upgraded. It resumed observations in early August 2017, making its first detection on August 14 (together with the LIGO detectors); this was quickly followed by the detection of the GW170817 gravitational wave, the only one observed with classical methods (optical, gamma-ray, X-ray and radio telescopes) as of 2024.[5] The detector is used for joint observing runs with the other detectors, separated by commissioning periods during which it is upgraded to increase its sensitivity and scientific output.[6]

  Country with institutions contributing to EGO and the Virgo Collaboration as of 2021
  Country with institutions contributing to the Virgo Collaboration as of 2021
  1. ^ "Our mission". www.ego-gw.it. European Gravitational Observatory. Retrieved 11 October 2023.
  2. ^ "The Virgo Collaboration". virgo-gw.eu. The Virgo Collaboration. 18 February 2021. Retrieved 11 October 2023.
  3. ^ Cite error: The named reference dcc.ligo.org was invoked but never defined (see the help page).
  4. ^ "Virgo Interferometer for the Detection of Gravitational Waves". eoPortal. 1 April 2019. Retrieved 26 July 2024.
  5. ^ Cite error: The named reference Abbott-2017b was invoked but never defined (see the help page).
  6. ^ "IGWN | Observing Plans". observing.docs.ligo.org. Retrieved 16 January 2024.