Gravitational Waves

The Astronomical Observatory of the University of Warsaw participates in the LIGO-Virgo-KAGRA project, an international collaboration focused on the detection of gravitational waves—ripples in spacetime predicted by Albert Einstein in 1916 as part of his General Theory of Relativity. Einstein himself believed detecting these waves would be impossible because their amplitudes are extremely small, but modern successors proved him wrong. Today, gravitational waves are not only confirmed to exist, but can also be observed using advanced detectors.

The LIGO-Virgo-KAGRA (LVK) project uses powerful interferometric detectors to measure the minuscule distortions caused by passing gravitational waves. One detector, Virgo, is located near Pisa, Italy. In Poland, a seismic and infrasound monitoring subsystem was built as part of the Virgo collaboration. Two LIGO detectors (Laser Interferometer Gravitational-Wave Observatory) are located in Livingston and Hanford, USA. In Japan, the KAGRA detector (Kamioka Gravitational Wave Detector) is operational.

Since 2008, researchers from the University of Warsaw Observatory, as members of Virgo-POLGRAW, have analyzed data from these detectors, studying the strongest gravitational-wave sources, including binary black holes, neutron stars, rotating neutron stars, explosive events such as supernovae, and monitoring noise sources around the Virgo detector. They participated in the first groundbreaking detection of gravitational waves in 2015—GW150914 (GW stands for gravitational wave). This signal originated from the merger of two black holes, a prediction that Warsaw scientists had foreseen as likely for the first observed gravitational-wave event.

Observations conducted since 2015 during three observing campaigns have revealed two neutron star mergers, two to three neutron star–black hole mergers, and more than eighty binary black hole mergers.

These discoveries allow researchers to address fundamental questions in astrophysics and cosmology and to test predictions of Einstein’s General Theory of Relativity in strong gravitational fields. The fourth observing campaign is currently underway.