The international network of gravitational wave detectors operated by the LIGO–Virgo–KAGRA (LVK) Collaboration has announced today the online release of an updated catalog of all gravitational wave events observed to date, named the Gravitational Wave Transient Catalog-5.0 (GWTC-5.0), with the corresponding scientific papers being submitted to Astrophysical Journal and Astrophysical Journal Letters. The data analyzed in this work were collected by the twin detectors of the US National Science Foundation Laser Interferometer Gravitational-wave Observatory (NSF LIGO) and the Virgo detector operated by the European Gravitational Observatory (EGO), with analysis carried out in collaboration with the KAGRA Collaboration, an international consortium centered on the KAmioka GRAvitational wave detector in Japan.
This updated catalog includes the most recent gravitational wave events that occurred between April 10, 2024 and January 28, 2025, during a portion of the fourth observing run (O4) known as O4b. During this period, 161 new gravitational wave events were detected, bringing the total number of confirmed events observed by the network since the first detection in 2015 to an astounding 390.
"Nearly 400 gravitational-wave events accumulated in our catalog have ushered us into a new era of statistical astronomy—where this growing collection of detected signals enables population studies and tests of general relativity with unprecedented precision," said Leo Tsukada of the University of Nevada Las Vegas. "Crucially, the inclusion of Virgo in our detector network has been transformative: its independent measurements allow us to triangulate sources across the sky with a few square degree accuracy, turning fuzzy patches of uncertainty into sharp localizations that can be used to motivate multi-messenger follow-up campaigns. This sets a strong foundation for the next-generation observing era with an expanded global detector network."
With the release of the updated catalog, the fourth observing run alone now accounts for roughly 75% of all gravitational wave events detected since the first observation in 2015—the span of nearly a decade. This impressive result demonstrates how crucial detector upgrades are for increasing sensitivity, leading to an extraordinary growth in the number of detected events with each successive observing run. In fact, the international LVK Collaboration alternates periods of data collection (observing runs) with phases devoted to detector upgrades and commissioning. That's also why the gravitational wave event catalog—including validated data and the physical parameters of the sources—is updated and shared with the wider scientific community periodically.
"We are now seeing the impacts of gravitational-wave astronomy across the scientific community," said Jonah Kanner, a senior scientist for the LIGO Laboratory at Caltech. "Our data releases are cited in over 200 scientific papers each year, and thousands of young and aspiring scientists have enrolled in our annual Open Data Workshops. This data set will be a treasure trove for researchers learning about cosmology, stellar evolution, theories of gravity, and many other open questions in physics and astronomy."
In addition to the new perspectives opened by this extraordinary number of observations, the new catalog also includes several detections that are themselves exceptional and sets new records in gravitational-wave astronomy observations: the best sky localization ever achieved for a gravitational wave source, the clearest gravitational wave signal ever recorded, and evidence for the existence of second-generation black holes.
The Best Sky Localization Ever Achieved
A signal detected by the two LIGO detectors in the United States and Virgo in Europe on June 15, 2024—and therefore called GW240615—set the record for the most precise sky localization among all gravitational wave events observed to date. The source was identified within an area of just 6 square degrees, a relatively small portion of the celestial sphere. This exceptional performance was achieved thanks to the triangulation using data from all three detectors active at the time, including Virgo, which rejoined the observing campaign in April 2024 at the beginning of O4b, contributing significantly to the network's source-localization capabilities.
Localization of sources in the sky enables astronomers to search for other astronomical signals that may be associated with the gravitational wave event. "We knew that Virgo's contribution would be decisive in improving the localization of observed gravitational wave sources," said Marie Anne Bizouard, spokesperson for the Virgo Collaboration, and researcher at the French National Centre for Scientific Research (CNRS) in Nice. "We are proud of the outstanding work carried out by the team responsible for commissioning the detector, which has been rewarded by this record-setting result."
The gravitational wave event observed with this record localization was the merger of two black holes, with masses of about 26 and 30 solar masses, which violently collided more than 3 billion light-years from Earth.
Improvements in the network's ability to localize events, along with the increase in the size of the dataset, also allowed for a better estimate of the Hubble constant, H0, whose precise value is the subject of significant ongoing tension in cosmology.
"The Hubble constant tells us how fast the Universe is expanding and how old it is," said Hsin-Yu Chen from the University of Texas at Austin. "However, different methods of measuring it continue to give conflicting answers, creating the long-standing 'Hubble tension' in cosmology. If this discrepancy persists, it could mean that our current understanding of the universe is incomplete. Using a new set of gravitational-wave sources, we obtain an independent measurement of the Hubble constant with about 25% improved precision over previous results. This significant advance highlights the growing power of gravitational-wave astronomy and brings us closer to resolving one of the biggest puzzles in modern cosmology."
The Clearest Gravitational Wave Signal Ever Recorded
Detecting gravitational waves does not simply mean capturing a signal, but extracting it from the noise that disturbs the detectors. This requires intense noise-mitigation efforts and highly sophisticated data analyses, which is why the "strength" or "clarity" of a signal is expressed through the signal-to-noise ratio (SNR). The catalog published today includes the "clearest" gravitational wave signal ever detected, with a signal-to-noise ratio of 76.9. This signal, GW250114 ( previously announced during celebrations of the 10th anniversary of the first detection of gravitational waves) reached Earth on January 14, 2025 and was generated by the merger of two black holes with nearly identical masses (32 and 34 times the mass of the Sun, respectively), occurring more than one billion light-years from Earth. Its "clarity" has led to some exceptional scientific results, which have already been published and announced by the LVK collaboration in recent months, including the most accurate test of general relativity ever performed and confirmation of Stephen Hawking's black hole area theorem.
Second Generation Black Holes
Another outstanding result, included in the new catalog published today—though it had already been announced by the LVK Collaboration in recent months—concerns two very special events: GW241011 and GW241110. These signals, detected in October and November 2024, just one month apart, were generated by two black hole mergers, located approximately 700 million and 2.4 billion light-years from Earth, respectively. Certain characteristics of these mergers—in particular the spin of the black holes (that is, the orientation and rate of their rotations)—indicate the objects involved could be 'second-generation' black holes, meaning black holes that are themselves the result of previous coalescences. These objects likely formed in very dense and crowded cosmic environments, such as stellar clusters, where black holes are more likely to collide and merge repeatedly.
"Each new detection provides important insights about the universe, reminding us that each observed merger is both an astrophysical discovery but also an invaluable laboratory for probing the fundamental laws of physics," says Carl-Johan Haster, assistant professor of astrophysics at the University of Nevada, Las Vegas. "Binaries like these had been predicted given earlier observations, but this is the first direct evidence for their existence."
The growing number of observed events has also enabled researchers to study and, increasingly, clearly identify the properties of different populations of black holes. In particular, they now find that these second-generation black holes may form a distinct sub-group that shares certain characteristic properties. One of the companion papers released alongside the catalog explores this and other black hole populations in detail.
There is still more data to analyze from the fourth observing run, with the final portion set to be publicly released in December. The LVK Collaboration celebrates this significant update to the catalog of observed gravitational wave events, the global team that made it possible, and the discoveries still to come.
"We have an outstanding team of scientists, engineers and supporting staff who build, operate and improve these amazing detectors, and who analyze the data with great care to answer scientific questions," said Peter Shawhan, Deputy Spokesperson of the LIGO Scientific Collaboration and professor of physics at the University of Maryland. "Some keep the observatories at peak performance while many others work and study at universities, colleges and research institutions near and far away. It's the global, interconnected team of creative, dedicated people which makes the most ambitious science possible."
