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Albert Einstein was right: There is an area at the edge of black holes where matter can no longer remain in orbit and instead falls into it, as predicted by the theory of gravity.
Using telescopes capable of detecting X-rays, a team of astronomers has observed for the first time this area, called the “subduction zone”, in a black hole about 10,000 light-years from Earth. “We were ignoring 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 understand it, we can’t explain it any other way.”
This isn’t the first time black holes have helped confirm Einstein’s grand theory, also known as general relativity. The first photograph of a black hole, taken in 2019, had previously strengthened the revolutionary physicist’s fundamental assumption that gravity was merely matter bending the fabric of space-time.
Many of Einstein’s other predictions turned out to be correct over the years; these included gravitational waves and the universal speed limit. “He’s a tough guy to bet against at this point,” said Mummery, a Leverhulme-Peierls Fellow in physics at the University of Oxford in the United Kingdom.
“We specifically went out looking for this; that was always the plan. “We’ve been debating for a long time whether we’d find it,” Mummery said. “People said it would be impossible, so it’s really exciting to confirm that it’s there.”
‘Like the edge of a waterfall’
The observed black hole is within a system called MAXI J1820+070, which consists of a star smaller than the sun and the black hole itself, estimated to be 7 to 8 solar masses. Astronomers used NASA’s space-based NuSTAR and NICER telescopes to collect data and understand how hot gas, called plasma, from the star is sucked into the black hole.
NuSTAR stands for Earth-orbiting Nuclear Spectroscopic Telescope Array, and NICER, formally known as the Neutron Star Interior Composition Explorer, is located on the International Space Station.
“Around these black holes are large disks of orbiting material (from nearby stars),” Mummery said. “Most of it is stable, which means it can flow happily. It’s like a river, whereas the plunge zone is like the edge of a waterfall; all your support disappears and you crash headfirst. Most of what you can see is the river, but there’s a small area at the very end, which is basically what we found this,” he added, noting that although the “river” had been widely observed, this was the first evidence. “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 “subduction zone” light can still escape, but matter is doomed to annihilation due to the strong gravitational force. explained.
The study’s findings could help astronomers better understand the formation and evolution of black holes. “We can really learn about them by studying this area because it’s right on the border so it gives us the most information,” Mummery said.
What’s missing from the research is an actual image of the black hole because the black hole is so small and so far away. But another team of Oxford researchers is working on something much better than a picture: the first movie of a black hole. To achieve this, the team will first need to build the African Millimeter Telescope, a new observatory in Namibia that Mummery expects to be online within a decade. Joining the international Event Horizon Telescope collaboration that captured the groundbreaking 2019 image of the black hole, the telescope will allow scientists to observe and film massive black holes at the center of the Milky Way galaxy and beyond.
A link to the past
According to Christopher Reynolds, an astronomy professor at the University of Maryland at College Park, finding actual evidence for the “subducting zone” is an important step that will allow scientists to significantly improve models of how matter behaves around a black hole. “For example, it could be used to measure the spin rate of a black hole,” said Reynolds, who was not involved in the research.
Dan Wilkins, a research scientist at Stanford University in California, calls this an exciting development and points out that in 2018, a tremendously bright burst of light with extremely high energy occurred from one of the black holes in our galaxy. X-rays.
“We assumed at the time that this excess was due to hot material in the ‘subduction zone,’ but we didn’t have a full theoretical prediction of what this emission would look like,” Wilkins said. new work.
He added that this study actually performed this calculation, using Einstein’s theory of gravity to predict what X-rays emitted by material in the “subducting zone” would appear around a black hole, and compared it with data from that bright explosion on Earth. 2018.
“This will be a major area of discovery for the next decade as we look to the next generation of X-ray telescopes that will give us more detailed measurements of the innermost regions just outside the event horizon of black holes,” Wilkins said. .”
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