By AFP | 2026-07-03

Scientists have for the first time detected the "fingerprints" of a black hole's event horizon -- the boundary from which nothing can escape, according to research published June 24 in the journal Nature.

They made the discovery by studying ripples in space-time called gravitational waves that were created when two black holes violently smashed into each other.

A black hole's event horizon is known as the "point of no return" because not even light can avoid being swallowed into its darkness.

This has made them incredibly difficult to learn anything about.

But there is one event of such cataclysmic violence that it could offer a chance to glimpse this extreme phenomenon -- when two black holes merge into one.

When this cosmic death spiral occurs, it shoots gravitational waves across the universe which scientists have been detecting for the last decade.

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," said lead study author Sizheng Ma of the Perimeter Institute for Theoretical Physics in Canada.

"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."

Decoding the physics

The last stage of two black holes merging is like a spoon stirring a glass of water, Sizheng 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," Sizheng 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," said Columbia University gravitational wave astrophysicist Maximiliano Isi.

In the future, the team of scientists hope to find signs of tiny changes known as quantum fluctuation.

"In this way, we can really probe this near horizon region to look for a new physics," including searching for a deviation from general relativity, Sizheng Ma said.

'Compelling analysis'

Italian theoretical physicist Francesco Sannino, who studies black holes, said it was "compelling analysis" but needed to be checked by other researchers.

Still, it was "striking" that the scientists were able to show that gravitational waves carried the event horizon's "fingerprints," he said.

The astrophysicist Isi described the work as "tantalizing."

"More generally, understanding the physics of black holes and their mergers is important as it might shed light on how space and time are woven together at a more fundamental level," he said.

West Virginia University astrophysicist Sean McWilliams was skeptical that the gravitational wave frequency analyzed by the scientists was actually "dictated" by the event horizon.

For this reason, "the actual observed signal doesn't really tell us anything about the horizon or the other properties directly related to it," he said.

Sizheng Ma said McWilliams's statement was "not correct," suggesting he had conflated two different aspects in the paper.

"There is often considerable resistance and criticism in the early stages of promoting a new concept," he said, adding he is working on another paper to "clarify these confusions and possible misinterpretations."