LIGO-Virgo-KAGRA Unveils GWTC-4 Catalog Featuring 128 New Gravitational Wave Detections

In March 2026, the international LIGO-Virgo-KAGRA (LVK) collaboration reached a landmark achievement in gravitational wave astronomy by releasing the updated GWTC-4 catalog. Formally published in the peer-reviewed Astrophysical Journal Letters, this comprehensive dataset significantly expands the global registry of space-time ripples. These findings serve as a powerful validation of the general theory of relativity, which Albert Einstein first proposed back in 1915.

The GWTC-4 catalog introduces 128 newly identified gravitational wave sources detected during the first segment of the fourth observing run, known as O4a. This observation window spanned from May 2023 to January 2024. This latest release more than doubles the scope of the previous catalog, which contained 90 events gathered over three earlier campaigns. While a preliminary version 4.0 was shared with the public in August 2025, its formal scientific validation and official integration into the astronomical record occurred in 2026.

This new collection of detections encompasses a wide variety of compact object mergers, with binary black hole masses ranging from 5.79 to 137 solar masses. A standout discovery in this set is the event designated GW231123_135430, which is believed to be the most massive binary black hole merger documented to date. The wealth of new black hole data is instrumental in refining our understanding of stellar evolution and the specific mechanisms that govern the formation of these celestial objects. Furthermore, these observations assist scientists in narrowing down cosmological measurements, particularly the Hubble constant.

The global network of observatories driving these breakthroughs includes the Laser Interferometer Gravitational-Wave Observatory (LIGO) in the United States, the Virgo interferometer in Italy, and the Kamioka Gravitational Wave Detector (KAGRA) in Japan. Notably, the O4 cycle marked the first time KAGRA participated in data collection alongside LIGO and Virgo for the duration of the run. This fourth observing cycle, which commenced in May 2023 and concluded on November 18, 2025, stands as the longest operational period in the network's history. Out of approximately 250 real-time candidates identified during O4, 128 were verified for inclusion in GWTC-4.0, highlighting the significantly improved sensitivity of the detectors.

The release of GWTC-4 represents a monumental leap forward in observational astrophysics, providing a massive repository of data to test general relativity and study compact object populations across the universe. By documenting asymmetric mergers and the most massive collision ever recorded, the catalog offers essential empirical constraints for existing theoretical models. Looking ahead, the collaboration is preparing for its next six-month observation phase, labeled IR1. This upcoming cycle is tentatively scheduled to begin in late summer or early autumn of 2026, following a series of critical hardware upgrades and system enhancements.