Gravitational wave signals from the largest cosmic collision ever recorded may alter how scientists understand black holes, gravity, and the very universe, according to University of Copenhagen researchers in a pair of new papers.
After a dance that lasts millions of years, the final impact of two black holes is such a powerful cosmic event that it sends gravitational waves, distorting space and time, rippling across the universe. The cataclysmic events known as GW250114 and GW231123 were measured through recent advances in observation technology.
Gravitational Waves
“These are waves in spacetime itself—like ripples in water—that travel at the speed of light. They don’t move through space; they are waves of space: a rhythmic stretching and compression of the very structure of the universe,” explains co-author Jose Maria Ezquiaga from the Niels Bohr Institute.
Ezquiaga leads the LIGO-Virgo-KAGRA (LVK) collaboration, an international group using the most advanced observational platforms to study gravitational waves. By comparing data from observatories in the US, Europe, and Asia, they can triangulate highly accurate readings. This accuracy will be further enhanced in the future with the addition of a new observatory in India in the coming years.
Measuring these waves is a very challenging technical feat, with their disturbances requiring a resolution about 700 million times finer than a human hair, and the latest equipment advances by the LVK collaboration are necessary to capture the waves with such accuracy. In addition to the recent studies by Ezguiaga and colleagues, the LVK collaboration has also released a trove of other gravitational wave observations, doubling the total number available to researchers.
a Powerful Black Hole Merger
Despite being predicted by Einstein a century ago, it wasn’t until the last decade that humans measured gravitational waves for the first time. The GW250114 detection, forming the heart of the first new paper, published in Physical Review Letters, is the most powerful yet, involving two black holes weighing in at around 30 solar masses.
“The properties of this merger are a type we know well from previous measurements,” Ezquiaga said. “What makes this discovery truly exceptional is the very strong signal. It opens entirely new possibilities for testing our fundamental understanding of gravity and the nature of black holes.”
This time, the data appears to be confirming the work of noted physicist Stephen Hawking. With 99% certainty, the data reflect Hawking’s assertion that when two black holes merge into one, the new black hole has an area greater than the two originals combined. The new signal’s unprecedented strength and clarity provided the first evidence for the hypothesis, whereas earlier signals were too fleeting to make such a determination.
Unexpected Mass
Yet GW250114 was not the most impressive event captured by the LVK collaboration. That honor goes to the most powerful black hole merger on record, GW231123, consisting of 100 and 140-solar-mass black holes smashing together to form a 225-solar-mass black hole. Existing research indicates that finding binary black holes above 50 solar masses each is highly unusual. Eventually, the new black hole may grow to 260 solar masses, far outside of the typical range for similar black holes.
“The observation challenges our understanding of how black holes form,” Ezquiaga said. “Black holes of such large mass shouldn’t arise through ordinary stellar collapse.”
“One possibility is that the two black holes in this system were themselves formed by previous mergers of smaller black holes, but in truth, we don’t know,” Ezquiaga said. “It’s also possible that the signal was distorted as it traveled through the universe.”
A forthcoming paper on the GW231123 observation is currently undergoing peer review, and ongoing work on gravitational waves is expected to further enhance our understanding of the universe. Some of the new observational technologies used in recent research have also helped establish new benchmarks in lasers, optical systems, quantum computing, AI, and atomic clocks.
Fundamentally, for Ezquiaga and his colleagues, the team’s recent study has introduced both new insights and compelling new questions about the enduring mystery of black holes, how they form and change over time, and how astrophysicists perceive them.
The paper, “GW250114: Testing Hawking’s Area Law and the Kerr Nature of Black Holes,” appeared in Physical Review Letters on September 10, 2025.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.