“This is a really exciting result,” says Edward Cackett, an astronomer at Wayne State University who was not involved in the study. “Although we’ve seen X-ray echo signatures before, so far it has not been possible to separate the echo that comes behind a black hole and bends into our field of vision. It will allow better mapping of how things fall into black holes and how black holes bend space around them.”
Releasing energy through black holes, sometimes in the form of X-rays, is an absurdly extreme process. And since supermassive black holes release so much energy, they are basically powerful ones that allow galaxies to grow around them. “If you want to understand how galaxies form, you really have to understand these processes outside the black hole that are able to release these huge amounts of energy and energy, these incredibly bright light sources we study,” says Dan Wilkins, an astrophysicist at Stanford University and lead author of the study.
The study focuses on a supermassive black hole at the center of a galaxy called I Zwicky 1 (abbreviated I Zw 1), about 100 million light-years from Earth. In supermassive black holes like I Zw 1, large amounts of gas fall toward the center (the event horizon, which is basically a point of no return) and are harder to flatten onto the disk. Above the black hole, the meeting point of charged particles and the activity of the magnetic field results in the production of high-energy X-rays.
Some of these X-rays shine right at us and we can observe them normally with a telescope. But some of them also shine towards the flat disk of gas and will bounce off it. I black hole rotation I Zw 1 slows down faster than that seen in most supermassive black holes, causing easier falling of ambient gas and dust and powering the black hole from multiple directions. This in turn leads to higher X-ray emissions, which is why Wilkins and his team were particularly interested.
As Wilkins and his team observed this black hole, they noticed that the corona seemed to be “flashing”. These flashes, caused by X-ray pulses bouncing off a massive gas disk, came from behind the shadow of a black hole – a spot usually hidden from view. But because a black hole bends the space around it, X-ray reflections are also bent around it, which means we can spot them.
The signals were found using two different space telescopes optimized to detect X-rays in space: NuSTAR, operated by NASA, and XMM-Newton, operated by the European Space Agency.
The biggest implication of the new discoveries is that they confirm what Albert Einstein predicted in 1963 as part of his theory of general relativity – the way light should bend around huge objects like supermassive black holes.
“It’s the first time we’ve really seen a direct signature of the way light bends right behind a black hole in our field of vision,” because the way a black hole distorts the space around it, ”says Wilkins.
“While this observation does not change our overall picture of black hole accumulation, it is a nice confirmation that general relativity is important in these systems,” says Erin Kara, an astrophysicist at MIT who was not included in the study.
Despite the name, the supermassive black holes are so far away that they really look like individual points of light, even with the most modern instruments. It will not be possible to capture all of them the way scientists used the Event Horizon telescope to capture them shadow of supermassive black hole u galaxy M87.
So, although early, Wilkins and his team hope that discovering and studying more of these echoes from the bend could help us create partial or even full images of distant supermassive black holes. In turn, this could help them uncover some great mysteries about how supermassive black holes grow, sustain entire galaxies, and create environments in which the laws of physics are brought to extremes.