Birmingham researchers have played a central role in the latest results released by the LIGO-Virgo-KAGRA Collaboration.
The iconic "Masses in the Stellar Graveyard" plot is bursting at the seams with the addition of the latest verified gravitational wave (GW) detections made by the LIGO-Virgo-KAGRA (LVK) collaboration. The plot shows the masses of announced GW detections (blue and orange dots) alongside those of black holes and neutron stars observed or detected through electromagnetic (EM) observations, through January 2025. Here, they are sorted from lowest to highest masses showing clearly how LVK and GW detectors can observe objects in the universe mostly unobservable by EM means. It also illustrates just how efficient GW interferometers are at making such observations: LVK has made these detections in 9.5 years; the EM observations represent about 60 years-worth of searching. Image credit: LIGO-Virgo-KAGRA / Aaron Geller / Northwestern
The LIGO-Virgo-KAGRA Collaboration has released its fifth gravitational-wave catalogue, logging 161 new signals detected between 10 April 2024 and 28 January 2025. The tally now stands at 390 confirmed detections since the first observation in 2015.
GWTC-5.0 is a catalogue of firsts: the first evidence of binary black holes forged through distinct astrophysical processes; the sharpest sky localisation ever achieved for a black hole merger; and the loudest gravitational-wave signal ever recorded.
The signals were captured during the second leg of the fourth observing run using the two US National Science Foundation LIGO detectors and the Virgo detector in Europe. Analysis was carried out by the international LIGO-Virgo-KAGRA Collaboration, including KAGRA, the gravitational-wave detector in Japan. The full catalogue is freely available on the Gravitational-Wave Open Science Centre (GWOSC). Accompanying papers have been submitted to The Astrophysical Journal and The Astrophysical Journal Letters.
Researchers at the University of Birmingham's Institute for Gravitational Wave Astronomy played a central role across these results.
Professor Denis Martynov, Professor in Physics at the University of Birmingham, said: "The instruments have become so sensitive that in just nine months we have nearly doubled the number of binary black holes observed in the previous eight years."
The sheer scale of detections is reshaping our picture of the cosmos.
Professor Alberto Vecchio, Professor of Astrophysics, University of Birmingham, said: "We have now observed nearly 400 binary black holes. The Universe clearly has multiple ways of producing them — and we can start asking what this population is really telling us about mass, formation, and how these black holes find each other."
Arriving on 14 January 2025, GW250114 is the loudest gravitational-wave signal ever detected, with a signal-to-noise ratio of 76.9. It was produced by the merger of two near-identical black holes of roughly 32 and 34 solar masses, more than a billion light-years away.
Dr Geraint Pratten, Royal Society University Research Fellow at the University of Birmingham, said: "That single event has already delivered the most precise test of general relativity with gravitational waves to date, and the strongest gravitational-wave confirmation yet of Stephen Hawking’s black hole area theorem. GW250114 rang out so clearly that one collision gave us the sharpest test of Einstein’s theory yet. We know general relativity has its limits; we just need to find exactly where they lie."
Detected on 15 June 2024 by both LIGO detectors and Virgo, GW240615 has been localised to just 6 square degrees of sky — the most precise location ever pinned to a gravitational-wave event.
Dr Gregorio Carullo, Assistant Professor, University of Birmingham, said: "With our growing detector network, we are moving closer to the day when astronomers can routinely point a battery of telescopes at the exact site of a binary merger and learn far more about where and how these systems form."
Two events in GWTC-5.0, GW241011 and GW241110, provide some of the strongest evidence yet that some black holes may themselves be the products of earlier mergers. Such "second-generation" black holes are expected to form in dense stellar environments where black holes can repeatedly encounter and merge with one another.
Dr Patricia Schmidt, Associate Professor at Birmingham, said: “Gravitational waves are now letting us trace family trees for black holes. These events suggest that some of the black holes we observe today may themselves be the remnants of previous mergers, giving us direct insight into how black holes grow and evolve in crowded astrophysical environments.”
The final tranche of the data from the fourth science observing run is due for public release in December.
"We have worked incredibly hard over many months to prepare this new data release, and the instruments will begin taking new data again after the summer. I cannot wait to find out what the Universe has in store for us," says Professor Vecchio.
The detectors are currently being prepared for the next observing run, which is expected to deliver an even larger sample of gravitational-wave events.
Professor of Astrophysics
Staff profile for Professor Alberto Vecchio.
