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Albert Einstein was right: there is a region at the edge of black holes where matter can no longer remain in orbit and instead falls inward, as predicted by his theory of gravity.
Using telescopes that can detect X-rays, a team of astronomers has for the first time observed this region – called the ‘dive region’ – in a black hole about 10,000 light-years from Earth. “We ignored this region because we didn’t have the data,” said research scientist Andrew Mummery, lead author of the study published Thursday in the journal Monthly Notices of the Royal Astronomical Society. “But now that we do, we can’t explain it any other way.”
It is not the first time that black holes have helped confirm Einstein’s grand theory, also called general relativity. The first photo of a black hole, taken in 2019, had previously reinforced the revolutionary physicist’s core assumption that gravity is just matter bending the fabric of space-time.
Many of Einstein’s other predictions have proven correct over the years, including gravitational waves and the universal speed limit. “He’s a tough guy to bet against at the moment,” said Mummery, a Leverhulme-Peierls Fellow in the physics department at the University of Oxford in the United Kingdom.
“We specifically looked for this one – that was always the plan. We debated for a long time whether we could ever find it,” Mummery said. “People said it would be impossible, so it’s really exciting to confirm it’s there.”
NASA/CXC/M. Weiss
In an artist’s illustration, a black hole pulls material from a companion star, forming a disk that spins around the black hole before falling into it.
The observed black hole is in a system called MAXI J1820+070, which consists of a star smaller than the Sun and the black hole itself, estimated at 7 to 8 solar masses. The astronomers used NASA’s space-based NuSTAR and NICER telescopes to collect data and understand how hot gas called plasma is drawn from the star into the black hole.
NuSTAR is short for the Nuclear Spectroscopic Telescope Array, which orbits the Earth, and NICER, formally known as the Neutron Star Interior Composition Explorer, is located on the International Space Station.
NASA/JPL-Caltech
NASA’s space-based NuSTAR telescope, seen here in an artist’s concept, was first used to detect the “diving region” around a black hole.
“Around these black holes are large disks of orbiting material (from nearby stars),” Mummery said. “Most of it is stable, meaning it can flow happily. It’s like a river, while the falling area is like the edge of a waterfall: all your support is gone and you just fall headfirst. “Most of what you can see is the river, but there is a small area at the very end that is actually what we found,” he added, noting that while the “river” was commonly observed, this the first evidence is of the “waterfall.”
Unlike the event horizon, which is closer to the center of the black hole and does not allow anything to escape, including light and radiation, in the “diving region” light can still escape, but matter is doomed by the powerful force of gravity, Mummery explained .
The study’s findings could help astronomers better understand the formation and evolution of black holes. “We can really learn about it by studying this region because it’s right on the edge and so gives us the most information,” Mummery said.
One thing the study is missing is an actual image of the black hole, because it is too small and too far away. But another team of Oxford researchers is working on something even better than a photo: the first film of a black hole. To achieve that, the team will first have to build a new observatory, the Africa Millimeter Telescope in Namibia, which Mummery expects will be online within ten years. The telescope, which will join the international Event Horizon Telescope collaboration that captured the groundbreaking image of the black hole in 2019, will allow scientists to observe and film large black holes at the center of the Milky Way galaxy and beyond.
According to Christopher Reynolds, professor of astronomy at the University of Maryland, College Park, finding actual evidence for the “profound region” is an important step that will allow scientists to significantly refine models for how matter behaves around a black hole. “For example, it can be used to measure the rotation speed of the black hole,” says Reynolds, who was not involved in the study.
Dan Wilkins, a researcher at Stanford University in California, calls it an exciting development, pointing out that in 2018 there was a hugely bright burst of light from one of the black holes in our Milky Way, accompanied by an excess of high-energy radiation. X-rays.
“We hypothesized at the time that this excess came from the hot material in the ‘deep region,’ but we didn’t have a full theoretical prediction of what that emission would look like,” says Wilkins, who was also not involved in the study . new study.
This study actually does that calculation, he added, using Einstein’s theory of gravity to predict what the X-rays emitted by material in the “deep region” around a black hole would look like, and compares it with the data from that bright burst in the ‘deep’ black hole. 2018.
“This will be the key exploration space for the next decade,” Wilkins said, “as we look to the next generation of X-ray telescopes that will give us more detailed measurements of the inner regions just outside the event horizon of black holes. .”