Photo by NASA Hubble Space Telescope on Unsplash (illustrative)
On 10 September 2025, the international LIGO-Virgo-KAGRA collaboration announced GW250114, the clearest gravitational-wave signal yet detected. It reached the LIGO detectors in the United States on 14 January 2025 from two black holes colliding about 1.3 billion light-years away.
Key facts
The two black holes were about 34 and 32 times the mass of the Sun, similar to the first-ever detection in 2015, but the 2025 signal was dramatically clearer thanks to 10 years of noise reduction.
The black holes' combined surface area grew from about 240,000 to about 400,000 square kilometers, confirming Hawking's 1971 area theorem with 99.999% confidence, up from 95% in a 2021 test.
Scientists also measured two separate 'ringing' tones of the final black hole, a precise test of Einstein's general relativity.
About 300 black hole mergers have now been confirmed in a decade, and the detectors find roughly one every three days.
Why it matters
A theory about black holes that Hawking worked out on paper more than 50 years ago has now been checked directly in nature. The result shows how far gravitational-wave astronomy has come in its first decade, through steady work by scientists in many countries.
Worth noting
Only the two LIGO detectors were observing when this signal arrived; Virgo in Italy and KAGRA in Japan are part of the wider network. The study was published in Physical Review Letters.