'Fingerprints' of Black Hole's Event Horizon Detected For First Time (phys.org) 4
Researchers say they detected the first gravitational-wave "fingerprints" of a black hole's event horizon by analyzing the final moments of the powerful GW250114 merger. The findings support Einstein's general relativity and may eventually help probe frame dragging and quantum fluctuations near black holes. Phys.org reports: For the new research published in Nature, an international team of researchers analyzed data from the strongest gravitational wave ever recorded, known as GW250114, detected by the LIGO observatory in January 2025. By isolating the last burst of waves -- known as "direct waves" -- from this black hole merger, the scientists said they were able to extract information from closer to an event horizon than ever before. "This black hole horizon concept normally appears in science fiction," lead study author Sizheng Ma of the Perimeter Institute for Theoretical Physics in Canada told AFP. "But now we are really able to touch the region around the horizon with gravitational data," he added. "Sometimes I cannot believe this is really happening."
The last stage of two black holes merging is like a spoon stirring a glass of water, Ma explained. The resulting swirl in space creates the ripple of gravitational waves that travel at the speed of light in all directions. If the metaphorical spoon is stirring close enough to the black hole's event horizon, "this offers us a chance to decode the physics around that region," Ma said. By supporting the theory of general relativity, the results "proved that Einstein was correct again," he added.
The scientists emphasized that more research was needed to decipher what can be gleaned about event horizons using this method. But they did detect information about how black holes twist space around themselves as they rotate -- a phenomenon known as "frame dragging." "This is similar to pushing a glass into a table and twisting it, so that the tablecloth winds up around it," Maximiliano Isi, a gravitational wave astrophysicist at Columbia University, told AFP. In the future, the scientists hope to find signs of tiny changes known as quantum fluctuations. "In this way, we can really probe this near-horizon region to look for new physics," including searching for a deviation from general relativity, Ma said.
The last stage of two black holes merging is like a spoon stirring a glass of water, Ma explained. The resulting swirl in space creates the ripple of gravitational waves that travel at the speed of light in all directions. If the metaphorical spoon is stirring close enough to the black hole's event horizon, "this offers us a chance to decode the physics around that region," Ma said. By supporting the theory of general relativity, the results "proved that Einstein was correct again," he added.
The scientists emphasized that more research was needed to decipher what can be gleaned about event horizons using this method. But they did detect information about how black holes twist space around themselves as they rotate -- a phenomenon known as "frame dragging." "This is similar to pushing a glass into a table and twisting it, so that the tablecloth winds up around it," Maximiliano Isi, a gravitational wave astrophysicist at Columbia University, told AFP. In the future, the scientists hope to find signs of tiny changes known as quantum fluctuations. "In this way, we can really probe this near-horizon region to look for new physics," including searching for a deviation from general relativity, Ma said.
