Gravitational Wave Catalog Hits 390 Events, Offering New Clues to Cosmic Expansion and Einstein’s Legacy
The international LIGO, Virgo, and KAGRA (LVK) collaboration has released an updated gravitational wave catalog, bringing the total number of confirmed events since 2015 to 390. The latest compilation includes new detections that improve measurements of the universe's expansion rate and provide stringent tests of general relativity.
Catalog Updates and Data Periods
The collaboration has released the Gravitational Wave Transient Catalogue-5.0 (GWTC-5), which contains 161 new gravitational wave events detected between April 10, 2024, and January 28, 2025. This data corresponds to the second portion of the fourth observing run (O4b). The fourth observing run overall contributes approximately 75% of all detected events.
An earlier catalog, GWTC-4.0, included 128 events observed between May 2023 and January 2024 during the O4a observation cycle, which more than doubled the previous catalog's 90 signals.
The total number of confirmed gravitational wave events since the first detection in 2015 now stands at 390. The associated scientific papers have been submitted to the Astrophysical Journal and Astrophysical Journal Letters.
Notable Events
GW240615 (June 15, 2024)
This event achieved the best sky localization ever recorded for a gravitational wave signal, localized within 6 square degrees using data from the LIGO and Virgo detectors.
The source was a binary black hole merger with masses of approximately 26 and 30 solar masses, located at a distance of approximately 3 billion light-years.
GW250114 (January 14, 2025)
This event produced the highest signal-to-noise ratio ever recorded for a gravitational wave, measuring 76.9. The clarity of the signal enabled measurement of three vibrational tones of the resulting black hole, which matched general relativity predictions.
The source was a binary black hole merger with masses of approximately 32 and 34 solar masses, located at a distance of approximately 1 billion light-years. The event also confirmed Stephen Hawking's black hole area theorem.
GW241011 (October 2024) and GW241110 (November 2024)
These events exhibit characteristics suggesting the black holes involved may be second-generation objects resulting from previous mergers. GW241011 is located at a distance of approximately 700 million light-years, and GW241110 at approximately 2.4 billion light-years.
GW231123
This event represents the most massive black hole binary detected to date using gravitational waves, with each black hole estimated at approximately 130 solar masses.
This suggests the black holes may have formed from previous collisions of lighter black holes.
GW231118
This event featured a black hole binary with the largest mass asymmetry observed, where one black hole was twice the mass of the other.
GW231028
This event involved a black hole binary in which both black holes exhibited high spins, rotating at approximately 40% of the speed of light.
Cosmological and Astrophysical Implications
Hubble Constant Measurement
The updated catalog yields a measurement of the Hubble constant at H0 = 71.0(-7/+9) km s⁻¹ Mpc⁻¹. An earlier catalog estimate suggested a rate of 76 km s⁻¹ Mpc⁻¹. These values are consistent with other measurements but are not precise enough to resolve the Hubble tension, which refers to the discrepancy between different methods of calculating the universe's expansion rate.
Researchers from the University of Illinois Urbana-Champaign and the University of Chicago have proposed a technique called the stochastic siren method, which uses background gravitational waves from numerous distant collision events. This method, when applied to existing data, indicated higher Hubble constant values and a more rapid universal expansion rate. Current detectors are not yet sensitive enough to detect the gravitational wave background, but increased sensitivity over the next six years may allow this method to provide an independent measurement of the Hubble constant.
Tests of General Relativity
The signal from GW250114 enabled the most precise test of general relativity via gravitational waves to date, with all measurements matching theoretical predictions.
Researchers also utilized GW230814, identified as one of the strongest gravitational wave signals in the catalog, for detailed examination, finding no deviations from Einstein's theory.
Black Hole Populations
A subgroup of black holes with masses of 10–20 solar masses and rapid spins suggests the presence of second-generation black holes. Scientists propose that these highly spinning black holes may be products of earlier collisions, likely formed in dense stellar clusters.
Collaboration and Methodology
The LVK collaboration involves the LIGO detectors in the United States, the Virgo detector in Italy, and the KAGRA detector in Japan. The collaboration alternates observing runs with detector upgrades. The final portion of O4 data is scheduled for public release in December.