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When the scientists first turned NuSTAR and XMM-Newton X-ray space telescopes to a supermassive black hole at the center of a distant galaxy with the memorable name of IZwicky1, they knew their mission:
How can it be that some of nature’s darkest forces are also some of the brightest? Black holes are called black holes for a reason. However, the hot gases that fall into black holes become overheated and glow intensely.
It was a question the international team sought to resolve. Instead, they ended up confirming Albert Einstein’s theory of general relativity in one of his most extreme tests to date.
Through a chance observation of unusually bright X-ray flares around the supermassive black hole and careful analysis of the “echoes” from the eruption, the researchers were able to prove that what they were actually seeing were X-ray reflections. derived from behind the black hole.
The massive gravity of the black hole was bending the x-ray light into the corner, so to speak.
“It’s really further confirmation that this slight bending still works as Einstein predicted, even when gravity gets really strong and very close to a black hole,” Wilkins said. Reverse. Wilkins is the first author of the article and a researcher at Stanford University.
“This confirms what we already knew,” he says, “but on a more extreme scale.”
These results were published Wednesday in the journal Nature.
What’s up – In his Relativity: The Special and General Theory, Einstein discusses two interrelated theories – one being general relativity, a concept proposed in 1915.
The theory of general relativity suggests that a massive object can warp the space-time around it, creating what we feel like gravity. This facet of the theory has been proven over and over again, perhaps most notably during a solar eclipse in 1919, when astronomer Arthur Eddington confirmed that the sun’s gravity distorted starlight – just like Einstein l ‘had predicted.
“It is the gravitational lens at its the most extreme. ”
Astronomers have since used the gravity of distant galaxies to see around them to even more distant objects, a phenomenon known as the “gravitational lens”.
But this new work takes the gravitational lens to a whole new level, according to Wilkins.
“It’s not just the light that is reflected a little. It comes from everything behind the black hole, bends all around in our line of sight, ”he says. “This is the gravitational lens at its most extreme.”
How they did it – When stellar gas and dust fall into a supermassive black hole, it flattens out and revolves around it in a disc, like water flowing down a sewer, Wilkins says. This creates a high intensity glow in the visual and radiographic portions of the electromagnetic spectrum.
His team was measuring x-rays when “suddenly it started emitting what we call x-ray flares,” he says. “Suddenly the x-rays became about 2.5 times brighter for a very short period of time.”
The extremely bright flares reflect or echo off the rotating hot gas disk around the black hole.
Echoes and the eruptions that cause them are known phenomena, but Wilkins says the team has started to notice additional echoes they had not anticipated.
“These are the echoes from the back of the disc,” he says. “The echoes that emerge from the other side of the disc – the part hidden by the shadow of the black hole – actually curve around the edge of the black hole.”
Why is this important – Overall, the new findings add one more brick to the column of evidence supporting general relativity. There are also implications for a better understanding of galaxies, stars, and black holes themselves.
Most galaxies are believed to contain a supermassive black hole at their center, including our own Milky Way. A better understanding of how these supermassive black holes work could help scientists better understand their possible role in the formation of galaxies, according to Wilkins.
And in the process of verifying the gravitational curvature of x-rays around this particular supermassive black hole, the researchers also developed a new tool to help them study other black holes. Most of these objects are too far away to photograph, but Wilkins says they can now use x-ray echo measurements as a kind of sonar “to reconstruct this image, this map, from the extreme environment to the sea. ‘outside a black hole’.
And after – The immediate next step for Wilkins and other researchers is to refine new techniques to get better measurements of x-ray echoes, as well as a better picture of what the area around a black hole actually looks like.
New X-ray space telescopes, such as the European Space Agency’s Advanced Telescope for High Energy Astrophysics (ATHENA) – scheduled for the early 2030s – could be of great help.
“This will be the largest x-ray telescope we’ve ever launched and with a bigger telescope we’ll have a much more detailed view,” Wilkins said. “We will get an increasingly clear picture of this extreme environment just outside the black hole and find out what happens to this gas in its final moments before it falls.”
Abstract: The innermost regions of the accretion discs around black holes are strongly irradiated by X-rays emitted by a highly variable compact crown, in the immediate vicinity of the black hole. X-rays that are seen reflected from the disc, and delays, such as changes in the X-ray emission echo or “reverberate” from the disc provide a view of the environment just outside the disc. horizon of events. I Zwicky 1 (I Zw 1) is a galaxy close to Seyfert 1 with narrow lines. Previous studies of X-ray reverberation from its accretion disk revealed that the corona is made up of two components: an extensive, slowly varying component spanning the surface of the internal accretion disk, and a collimated nucleus. , with fluctuations in brightness propagating upward from its base, which dominates the faster variability. We report here observations of X-ray flares emitted around the supermassive black hole in I Zw 1. X-ray reflection from the accretion disk is detected through a relativistically widened iron K-line and a Compton bump. in the X-ray emission spectrum. Analysis of the X-ray flares reveals short flashes of photons consistent with the re-emergence of emissions behind the black hole. The energy shifts of these photons identify their origins from different parts of the disk. These are photons that reverberate from the other side of the disk and are bent around the black hole and amplified by the strong gravitational field. The observation of photons bent around the black hole confirms a key prediction of general relativity.
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