Universe now shows twice as many spacetime ripples from compact-object collisions

The LIGO‑Virgo‑KAGRA collaboration released GWTC-4, a catalog of 128 gravitational-wave sources detected during the fourth observing run (May 2023–Jan 2024), roughly doubling the published list of black hole and neutron star mergers; the dataset includes very massive and fast-spinning black hole collisions and two new mixed black hole–neutron star mergers.

The LIGO‑Virgo‑KAGRA (LVK) collaboration has published a new catalog of gravitational-wave detections that substantially enlarges the known set of compact-object collisions. The catalog, called GWTC-4, lists 128 sources recorded during the fourth observing run between May 2023 and January 2024. Gravitational-wave astronomy began with a 2015 detection and has since tracked collisions of black holes, neutron stars, and mixed pairs across large cosmic distances. This release highlights a wider variety of merger types and more extreme object properties than earlier catalogs. Key findings: - GWTC-4 includes 128 gravitational-wave sources recorded during the fourth LVK observing run (May 2023–Jan 2024). - Earlier published tallies from the first three observing runs included about 90 potential sources, and roughly 170 additional candidate detections have been reported but are not yet in this catalog. - The catalog reports very massive black hole binaries, with some component masses near 130 times the mass of the Sun, and systems with strongly unequal masses. - Several black holes in the sample are inferred to be spinning at rates near 40% of the speed of light, and scientists note these spins may result from prior merger chains. - GWTC-4 contains two new mixed mergers between black holes and neutron stars, and detections span distances from about 1 billion to about 10 billion light‑years. - LVK members reported that the expanded dataset supports continued tests of general relativity and studies of how black holes form and grow. Summary: The new catalog increases the sample available for studying the formation, masses, spins and merger histories of compact objects and shows a broader range of event types than previously published. LVK scientists say the results allow more precise tests of general relativity and give evidence consistent with past merger chains contributing to very massive, fast‑spinning black holes. The LVK results are due to appear in a special edition of the Astrophysical Journal Letters, and further analysis and future observing runs are expected to add more detections.