A recently discovered black hole merger is proving correct theoretical predictions made by Albert Einstein and Stephen Hawking, thanks to new observations by the Laser Interferometer Gravitational-Wave Observatory (LIGO), analyzed by researchers from the Flatiron Institute’s Center for Computational Astrophysics.
Maximiliano Isi and Will Farr led the recent work, shedding new light on the fundamental nature of space-time and the properties of black holes through their investigation of signal GW250114. Crucially, the analysis provides new hints for the long-sought reconciliation of general relativity and quantum physics.
What Black Holes Are
“This is the clearest view yet of the nature of black holes,” says Isi, who is also an assistant professor at Columbia University. “We’ve found some of the strongest evidence yet that astrophysical black holes are the black holes predicted from Albert Einstein’s theory of general relativity.”
Black holes are the final stage of stellar evolution, when a star’s mass collapses in on itself to create a density so powerful that even light cannot escape. The collision of these extreme densities is so powerful that it produces space-time ripples called gravitational waves, which fan out across the universe. Analyzing these ripples provides researchers with information about their originating events and reveals the black holes’ properties.
Using laser techniques, dedicated observatories such as LIGO, Virgo, and KAGRA can precisely measure the stretching and compression of space-time that gravitational waves create. The recent GW250114 measurement, some 10 years after IGO discovered its first instance of such an event, indicated the birth of a 63 solar mass blackhole rotating 100 times per second. In the intervening decade, technical improvements have allowed for a much clearer view of these cosmic events.
Improved Precision
“The new pair of black holes are almost twins to the historic first detection in 2015,” Isi says. “But the instruments are much better, so we’re able to analyze the signal in ways that just weren’t possible 10 years ago.”
The new data provided information from the entire duration of the event, measured only in milliseconds, beginning with the initial impact and ending with the final merger. As a merger progresses, its intensity wanes, which left researchers uncertain about the exact moment the merger was completed in earlier events, as the vibration merged with the black hole’s regular hum.
Prior to this most recent observation, Isi led a team in the development of a new frequency isolation technique based on data collected from the original 2015 event. These new, more precise readings, combined with the innovative method, allowed the team to isolate the merger from the final black hole as never before. This provides important data to test the murkier elements of scientists’ understanding of black holes.
“Ten milliseconds sounds really short, but our instruments are so much better now that this is enough time for us to really analyze the ringing of the final black hole,” Isi says. “With this new detection, we have an exquisitely detailed view of the signal both before and after the black hole merger.”
Thinking About Black Holes
Scientists have long speculated about black holes, with Roy Kerr’s 1963 equation to describe, based on Einstein’s general relativity, a major benchmark in the theoretical development. Spin and mass were the two characteristics that Kerr’s work argued were essential for describing a black hole, and now the new data prove from precise real-world observations that those characteristics are indeed all that is needed to describe one.
Another major development in black hole theory was Hawking’s area theorem from 1971, in which famed physicist Stephen Hawking demonstrated that an event horizon may only ever grow. Prior to his 2018 passing, Hawking had considered whether LIGO’s 2-15 merger observation would contain the data to prove his theorem, yet at the time, it remained out of reach. 2019 work that Isi’s team did with their enhanced processing techniques using the 2015 data offered some early suggestions that Hawking was correct, and now the more precise data has allowed them to gain even greater confidence in the theorem.
Finally, the second law of thermodynamics, stating that entropy must increase or remain the same over time, may be reflected in the new data in a way that may aid researchers attempting to reconcile relativity with quantum physics.
“It’s really profound that the size of a black hole’s event horizon behaves like entropy,” Isi says. “It has very deep theoretical implications and means that some aspects of black holes can be used to mathematically probe the true nature of space and time.”
Continuing Research
While LIGO has seen vast improvements in the last decade, the next one is expected to bring another tenfold boost to black hole merger detection precision.
“Listening to the tones emitted by these black holes is our best hope for learning about the properties of the extreme space-times they produce,” says Farr, who is also a professor at Stony Brook University. “And as we build more and better gravitational wave detectors, the precision will continue to improve.”
“For so long this field has been pure mathematical and theoretical speculation,” Isi says. “But now we’re in a position of actually seeing these amazing processes in action, which highlights how much progress there’s been — and will continue to be — in this field.”
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.