LIGO-Virgo-KAGRA Collaboration successfully wraps up its fourth Observing Run

Further exciting results anticipated from O4’s remaining parts

Today, the international LIGO-Virgo-KAGRA Collaboration celebrates the successful completion of its fourth observing run (O4), marking another major step forward in the exploration of the gravitational wave universe. The run, which began May 24, 2023 and continued through November 18, 2025, relied on coordinated observations and analyses by teams across the world. During O4, the detectors observed roughly 250 candidate signals in real time. Comprehensive analysis of the first (of three) segments of O4 yielded 128 significant events (an increase of around 50% compared to those announced in real time). These results were reported in the most recent update to the Gravitational-Wave Transient Catalog (GWTC-4.0). Data from the remaining two segments of O4 are currently under detailed examination. The collaboration expects that further results will emerge in the coming months as analyses continue.

Read more in the LIGO-Virgo-KAGRA Collaboration news item on ligo.org.