It was the strongest gravitational wave signal yet measured — what did it show? GW250114 was detected by both arms of the Laser Interferometer Gravitational-wave Observatory (LIGO) in Washington and Louisiana USA earlier this year. Analysis showed that the event was created when two black holes , each of mass around 33 times the mass of the Sun , coalesced into one larger black hole with a mass of around 63 solar masses. Even though the event happened about a billion light years away, the signal was so strong that the spin of all black holes , as well as initial ringing of the final black hole, was deduced with exceptional accuracy . Furthermore, it was confirmed better than before, as previously predicted , that the total event horizon area of the combined black hole was greater than those of the merging black holes . Featured, an artist’s illustration depicts an imaginative and conceptual view from near one of the black holes before collision. Illustration Credit: Aurore Simonnet ( SSU / EdEon ), LVK, URI; LIGO Collaboration https://science.nasa.gov/image-article/apod-2025-september-24-gw250114-rotating-black-holes-collide/