Gravitational wave provides strongest test yet of Hawking and Kerr black hole theories

Gravitational wave provides strongest test yet of Hawking and Kerr black hole theories
by Sophie Jenkins
London, UK (SPX) Sep 19, 2025
Scientists have confirmed two landmark theories about black holes using the most precise gravitational wave detection ever recorded. The LIGO - Virgo - KAGRA Collaboration reported the event, GW250114, with a signal-to-noise ratio of 80, enabling unprecedented validation of Stephen Hawking's area theorem and Roy Kerr's mathematical model of rotating black holes.

The event was detected by LIGO in the United States, with supporting observations from Virgo in Italy and KAGRA in Japan. Researchers determined that the merger involved two black holes, each around 32 times the Sun's mass. Their union increased the event horizon surface area from roughly 240,000 square kilometers to about 400,000, consistent with Hawking's 1971 prediction that black hole horizons never shrink.

The study also confirmed Kerr's 1963 solution, which showed that a black hole's characteristics can be defined by only two values: its mass and spin. During the ringdown phase, researchers identified two distinct gravitational wave frequencies, or "tones," matching Kerr's predictions of black hole "voices."

"GW250114 is the loudest gravitational wave event we have detected to date, it was like a whisper becoming a shout," said Geraint Pratten of the University of Birmingham. "This gave us an unprecedented opportunity to put Einstein's theories through some of the most rigorous tests possible."

The University of Birmingham played a central role, contributing hardware, waveform models, and data analysis. Ten years after the first gravitational wave detection in 2015, these results highlight how improved sensitivity has transformed gravitational wave astronomy into a precision science.

Patricia Schmidt, also from Birmingham, noted that the event was three times louder than the first gravitational wave detection: "This is owed to the tremendous technological improvements of our instruments, paving the path for precision astronomy with gravitational waves."

Gregorio Carullo, who coordinated one of the LVK analysis teams, emphasized the broader implications: "For the first time we could pick out two 'tones' from the black hole voices and confirm that they behave according to Kerr's prediction, obtaining unprecedented solid evidence for the Kerr nature of black holes found in nature."

Research Report:GW250114: testing Hawking's area law and the Kerr nature of black holes