Wikipedia:Today's featured article/February 21, 2025
The Virgo interferometer is a large-scale scientific instrument near Pisa, Italy, for detecting gravitational waves. The detector measures minuscule length variations in its two 3-km (1.9 mi) arms induced by the passage of gravitational waves. The project, named after the Virgo galaxy cluster, was first approved in 1992 and construction was completed in 2003. In 2015, the first observation of gravitational waves was made by the two other detectors, while Virgo was being upgraded. It resumed observations in early August 2017, making its first detection on 14 August; followed by the detection of the GW170817 gravitational wave, the only one also observed with classical methods (optical, gamma-ray, X-ray and radio telescopes) as of 2024. Virgo is hosted by the European Gravitational Observatory; the broader Virgo Collaboration, gathering 940 members in 20 countries, operates the detector, and defines the strategy and policy for its use and upgrades. (Full article...)