The discovery comes as the international LIGO-Virgo-KAGRA Collaboration released its latest catalogue of gravitational-wave detections – the largest and most detailed collection of black hole collisions ever assembled.
The observations were gathered using the twin Laser Interferometer Gravitational-wave Observatory (LIGO) detectors in the United States alongside the Virgo detector in Europe, which together form the world’s most advanced gravitational-wave observatory network.
At the centre of the research effort are scientists from OzGrav and Monash University who analysed nearly 400 gravitational-wave detections captured in the newly released Gravitational-Wave Transient Catalog (GWTC-5.0).
The findings provide compelling evidence that black hole binaries, pairs of black holes that eventually collide and merge, are not created through a single process. Instead, researchers said the universe appears to operate several different “cosmic assembly lines” capable of producing black holes in dramatically different environments.
Leading the Australian contribution was Dr Sharan Banagiri, a research fellow at Monash University’s School of Physics and Astronomy and OzGrav, who said the unprecedented dataset had allowed scientists to identify common characteristics among colliding black holes and neutron stars.
“This catalogue gives us a much clearer picture that black hole mergers are forming in several distinct ways,” Banagiri said.
“Some systems likely begin as enormous clouds of gas that collapse into massive stars before eventually becoming black holes. Others probably form inside dense star clusters, where black holes can drift together and collide. We’re also seeing evidence for black holes that may themselves be the products of earlier black hole mergers.”
The research, released as a preprint paper, found strong evidence for multiple sub-populations of merging black holes, suggesting the existence of several evolutionary pathways across the cosmos.
Among the most intriguing discoveries were rapidly spinning black holes unlike anything previously observed. Researchers found two distinct groups of these fast-spinning objects: one with masses between 10 and 20 times that of the sun, and another containing black holes more than 45 times heavier than the sun.
Dr Banagiri said the rotational speeds involved were almost impossible to comprehend.
“The sun rotates roughly once every 25 days,” he said.
“If the sun became a black hole and spun as quickly as some of the objects we’ve detected, it would rotate thousands of times every second.”
Researchers believe many of these rapidly spinning black holes may have formed through a process known as hierarchical merging where black holes produced by previous collisions merge again to create even larger and faster-spinning objects.
The study also found that the heaviest black holes, particularly those exceeding 45 solar masses, were more likely to merge with smaller companions nearby, providing further clues about how these exotic systems evolve over time.
Former Monash researcher and current Princeton University physicist Sylvia Biscoveanu said the latest catalogue represented a transformative moment for gravitational-wave astronomy.
“GWTC-5 marks the single largest expansion of the gravitational-wave catalogue so far,” Biscoveanu said.
“It includes extraordinary events, such as black holes with highly unequal masses and wobbling orbits caused by tilted spins, as well as the most precisely localised gravitational-wave event ever detected.”
Australian researchers said the expanding catalogue will provide astronomers with years of new data to explore, helping scientists better understand the life cycles of stars, the evolution of galaxies and the extreme physics governing black holes.
Eric Thrane, professor of physics and astronomy at Monash University and a chief investigator at OzGrav, said gravitational-wave astronomy was now entering a new era.
“We are moving beyond simply discovering individual events,” Thrane said.
“We are now building a statistical understanding of an entire population of cosmic collisions. What we’re seeing is a remarkable diversity of black holes – objects that are more massive, spinning faster and behaving in stranger ways than we had previously imagined.”
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