Scientists Just Doubled Our Catalog of Black Hole and Neutron Star Collisions

Source: Slashdot

Colliding black holes were first detected through spacetime ripples in 2015 by the Laser Interferometer Gravitational‑Wave Observatory (LIGO), notes Space.com.

Since then, LIGO and its partner detectors Virgo (Italy) and KAGRA (Japan) have observed a multitude of gravitational waves from colliding black holes, merging neutron stars, and even mixed mergers between a black hole and a neutron star. During the first three observing runs of LIGO, Virgo, and KAGRA, scientists “heard” 90 potential gravitational‑wave sources.

New GWTC‑4 Catalog

The LIGO‑Virgo‑KAGRA (LVK) Collaboration has now released data that adds 128 more gravitational‑wave sources to the catalog. These detections were collected during the fourth observational run (May 2023 – Jan 2024). Around 170 additional events detected by the three observatories have not yet been incorporated into the catalog.

• Gravitational‑Wave Transient Catalog‑4.0 (GWTC‑4) – the latest compilation of events from the fourth run.

Notable Findings

• Heaviest black‑hole binaries: Mergers involving black holes each about 130 M☉ (solar masses).
• Lopsided mergers: Systems with strongly mismatched component masses.
• Rapidly spinning black holes: Spins reaching roughly 40 % of the speed of light. These extreme properties likely result from prior collisions, providing evidence for merger chains that can grow black holes to masses billions of times that of the Sun.
• Mixed mergers: GWTC‑4 includes two new events involving a black hole and a neutron star.
• Distance extremes: Some neutron‑star mergers were detected up to 1 billion light‑years away, while certain black‑hole mergers originated from as far as 10 billion light‑years.

Scientific Impact

• Tests of General Relativity – The detections continue to confirm Einstein’s theory; however, increasingly precise predictions are needed to match the growing data set.
• Hubble constant measurements – Each merging black hole provides an independent measurement of the Hubble constant, and combining many events can substantially improve the accuracy of this cosmological parameter.
• Astrophysical insights – The catalog demonstrates the enhanced sensitivity of LVK detectors and reveals more massive, faster‑spinning, and otherwise unusual sources than previously observed.

Comments from LVK Members

“We are really pushing the edges, and are seeing things that are more massive, spinning faster, and are more astrophysically interesting and unusual.” – Daniel Williams, University of Glasgow

“So far, the theory is passing all our tests, but we have to make even more accurate predictions to keep up with all the data the universe is giving us.” – Aaron Zimmerman, University of Texas at Austin

“Every merging black hole gives us a measurement of the Hubble constant, and by combining all of the gravitational‑wave sources together, we can vastly improve how accurate this measurement is.” – Rachel Gray, University of Glasgow

“Each new gravitational‑wave detection allows us to unlock another piece of the universe’s puzzle in ways we couldn’t just a decade ago.” – Lucy Thomas, Caltech