Stanford astrophysicists report first detection of light from behind a black hole

So, something actually pretty awesome. In a paper published today in Nature astrophysicists have reported the first ever detection of light emitted from behind a black hole. Ya know, those things that have such a strong gravitational pull, light itself can't escape.

An analysis of X-ray flares from the innermost of region of a black hole's accretion disk revealed short flashes of photons with patterns consistent with emmision from behind the black hole.

Pretty much, x-rays and photons are bouncing around the accretion disk of the black hole in such a way that the photons could only have emerged from behind the black hole itself.

Such a thing was predicted by Einstein some time ago now, some long time and finally, for the first time, it has now been observed.
This means soon we may actually get a glimpse at the far.side of a black hole.

news.stanford.edu...

Link to study published in nature.

Watching X-rays flung out into the universe by the supermassive black hole at the center of a galaxy 800 million light-years away, Stanford University astrophysicist Dan Wilkins noticed an intriguing pattern. He observed a series of bright flares of X-rays – exciting, but not unprecedented – and then, the telescopes recorded something unexpected: additional flashes of X-rays that were smaller, later and of different “colors” than the bright flares.

According to theory, these luminous echoes were consistent with X-rays reflected from behind the black hole – but even a basic understanding of black holes tells us that is a strange place for light to come from.

“Any light that goes into that black hole doesn’t come out, so we shouldn’t be able to see anything that’s behind the black hole,” said Wilkins, who is a research scientist at the Kavli Institute for Particle Astrophysics and Cosmology at Stanford and SLAC National Accelerator Laboratory. It is another strange characteristic of the black hole, however, that makes this observation possible. “The reason we can see that is because that black hole is warping space, bending light and twisting magnetic fields around itself,” Wilkins explained.

The strange discovery, detailed in a paper published July 28 in Nature, is the first direct observation of light from behind a black hole – a scenario that was predicted by Einstein’s theory of general relativity but never confirmed, until now.

The leading theory for what a corona is starts with gas sliding into the black hole where it superheats to millions of degrees. At that temperature, electrons separate from atoms, creating a magnetized plasma. Caught up in the powerful spin of the black hole, the magnetic field arcs so high above the black hole, and twirls about itself so much, that it eventually breaks altogether – a situation so reminiscent of what happens around our own Sun that it borrowed the name “corona.”

“This magnetic field getting tied up and then snapping close to the black hole heats everything around it and produces these high energy electrons that then go on to produce the X-rays,” said Wilkins.

As Wilkins took a closer look to investigate the origin of the flares, he saw a series of smaller flashes. These, the researchers determined, are the same X-ray flares but reflected from the back of the disk – a first glimpse at the far side of a black hole.

Link to study published in nature.

Abstract from the study:

The innermost regions of accretion disks around black holes are strongly irradiated by X-rays that are emitted from a highly variable, compact corona, in the immediate vicinity of the black hole1,2,3. The X-rays that are seen reflected from the disk4, and the time delays, as variations in the X-ray emission echo or ‘reverberate’ off the disk5,6, provide a view of the environment just outside the event horizon. I Zwicky 1 (I Zw 1) is a nearby narrow-line Seyfert 1 galaxy7,8. Previous studies of the reverberation of X-rays from its accretion disk revealed that the corona is composed of two components: an extended, slowly varying component extending over the surface of the inner accretion disk, and a collimated core, with luminosity fluctuations propagating upwards from its base, which dominates the more rapid variability9,10. Here we report observations of X-ray flares emitted from around the supermassive black hole in I Zw 1. X-ray reflection from the accretion disk is detected through a relativistically broadened iron K line and Compton hump in the X-ray emission spectrum. Analysis of the X-ray flares reveals short flashes of photons consistent with the re-emergence of emission from behind the black hole. The energy shifts of these photons identify their origins from different parts of the disk11,12. These are photons that reverberate off the far side of the disk, and are bent around the black hole and magnified by the strong gravitational field. Observing photons bent around the black hole confirms a key prediction of general relativity.

a reply to: dug88

This is very cool.

We were just talking about multiple experiments to bend light.

Excuse me while I educate myself.

SnF

a reply to: dug88
That is so interesting. It is hard to fathom what a "black hole" is, a speck of dust with more mass than the earth? not too mention 800 million light years away.

originally posted by: FunshineCD
a reply to: dug88
That is so interesting. It is hard to fathom what a "black hole" is, a speck of dust with more mass than the earth? not too mention 800 million light years away.

A black hole isn't a physical object like a star or a planet. Rather, it's the region (or volume) of space where space-time distortion due to gravity is so strong even light cannot escape it. Each black hole is believed to contain a singularity at its centre - an infinitely small and infinitely dense point.

originally posted by: wildespace

originally posted by: FunshineCD
a reply to: dug88
That is so interesting. It is hard to fathom what a "black hole" is, a speck of dust with more mass than the earth? not too mention 800 million light years away.

A black hole isn't a physical object like a star or a planet. Rather, it's the region (or volume) of space where space-time distortion due to gravity is so strong even light cannot escape it.

So far so good.

Each black hole is believed to contain a singularity at its centre - an infinitely small and infinitely dense point.

I majored in physics and engineering, and I don't believe that, and none of my physics professors believed that. I never met a physicist who believes that, though I have heard them mention the singularity as a flaw in the mathematical theory. They aren't sure exactly what's inside the black hole, but they don't really think it's a singularity:

Does every black hole contain a singularity?

In the real universe, no black holes contain singularities. In general, singularities are the non-physical mathematical result of a flawed physical theory. When scientists talk about black hole singularities, they are talking about the errors that appear in our current theories and not about objects that actually exist. When scientists and non-scientists talk about singularities as if they really exist, they are simply displaying their ignorance.

A singularity is a point in space where there is a mass with infinite density. This would lead to a spacetime with an infinite curvature. Singularities are predicted to exist in black holes by Einstein's theory of general relativity, which is a theory that has done remarkably well at matching experimental results. The problem is that infinities never exist in the real world. Whenever an infinity pops out of a theory, it is simply a sign that your theory is too simple to handle extreme cases.

One of the "last frontiers" of physics is trying to come up with a theory to describe black holes without any singularities:

we will not know exactly what is going on in a black hole until scientists can successfully create a new theory that accurately describes small sizes and strong gravitational effects at the same time. Whatever the new theory ends up telling us, it will most certainly not say that there are singularities in black holes. If it did, that outcome would simply indicate that the new theory is just as bad as the old theory. In fact, one of the requirements for the future theory of everything is that it not predict singularities in black holes. In this sense, the interiors of black holes are the final frontier for theoretical physics. Just about everything else in the universe can be accurately described (at least in principle) using our current theories.

From the title I thought this thread would be about light from sources behind the black hole, like the galaxy behind the black hole in this animation:

But my guess was wrong, it's actually coming from the black hole's own halo which is outside the region where light can't escape, so light can escape, in a very interesting way in this case. It's interesting research.