First Detection of Light From Behind a Black Hole (phys.org) 20
Stanford University astrophysicist Dan Wilkins has spotted the first detection of light from behind a black hole. Phys.Org reports: "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.
"Fifty years ago, when astrophysicists starting speculating about how the magnetic field might behave close to a black hole, they had no idea that one day we might have the techniques to observe this directly and see Einstein's general theory of relativity in action," said Roger Blandford, a co-author of the paper who is the Luke Blossom Professor in the School of Humanities and Sciences and Stanford and SLAC professor of physics and particle physics.
The original motivation behind this research was to learn more about a mysterious feature of certain black holes, called a corona. Material falling into a supermassive black hole powers the brightest continuous sources of light in the universe, and as it does so, forms a corona around the black hole. This light -- which is X-ray light -- can be analyzed to map and characterize a black hole. [...] 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. [...] The mission to characterize and understand coronas continues and will require more observation.
"Fifty years ago, when astrophysicists starting speculating about how the magnetic field might behave close to a black hole, they had no idea that one day we might have the techniques to observe this directly and see Einstein's general theory of relativity in action," said Roger Blandford, a co-author of the paper who is the Luke Blossom Professor in the School of Humanities and Sciences and Stanford and SLAC professor of physics and particle physics.
The original motivation behind this research was to learn more about a mysterious feature of certain black holes, called a corona. Material falling into a supermassive black hole powers the brightest continuous sources of light in the universe, and as it does so, forms a corona around the black hole. This light -- which is X-ray light -- can be analyzed to map and characterize a black hole. [...] 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. [...] The mission to characterize and understand coronas continues and will require more observation.
Uhm. W T F? (Score:4, Informative)
"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"
That's about a stupid assumption. This is slashdot. We've been reading astronomy stories our whole lives. We know about gravity.
Re: (Score:1)
The scientist wasn't talking to Slashdotters. He was just calling attention to the fact that - naively - light emitted toward a viewer from the far side of a black hole would go straight into the black hole, so the viewer wouldn't see it.
Re: (Score:2)
Well, that's a stupid assumption, any layperson who reads the sciencey news knows that isn't true.
I don't believe you that a scientist said that. Maybe it was a journalist? Or a blogger?
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Re:Uhm. W T F? (Score:4, Funny)
"you can be pretty sure that no event horizon will exist according to a proper quantum gravity theory"
No I can't. There are more quantum gravity theories than there are quantum gravity theorists.
Regarding stuff coming out, maybe you are thinking of Hawking radiation, i.e., pairs of photons, one of which gets drawn into the blak hole and one which escapes to have lunch in the Restaurant at the End of the Universe. The escaping photon adds a bit of energy to the universe but the caught one adds a bit of negative energy to black hole causing it to shrink just a tiny bit. Eventually, the black hole "evaporates" but don't wait around for it, it will take over 10^{100} years.
However, this too is just a theory. We are currently advertising for black holes to fill out health inssurance forms so we can have them tested. . .pay kind of sucks though.
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Re: (Score:2)
That's about a stupid assumption. This is slashdot. We've been reading astronomy stories our whole lives. We know about gravity.
/. is no longer "news for news, stuff that matters," it's "news for commoners painted as news for news, dumbed down enough for the common folk to loosely comprehend the gist of it while feeling 'smart' and self-assured."
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It was always news for news, and it always will be.
Reflection (Score:5, Interesting)
From the abstract;
"The X-rays that are seen reflected from the disk, and the time delays, as variations in the X-ray emission echo or ‘reverberate’ off the disk, provide a view of the environment just outside the event horizon. ... 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."
This doesn't sound exactly like gravitational lensing...
Re:Reflection (Score:4, Informative)
From the abstract; "The X-rays that are seen reflected from the disk, and the time delays, as variations in the X-ray emission echo or ‘reverberate’ off the disk, provide a view of the environment just outside the event horizon. ... 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."
This doesn't sound exactly like gravitational lensing...
"bent around the black hole and magnified by the strong gravitational field" sounds exactly like gravitational lensing to me,
The bit about "reverberating" doesn't make any sense as written, but it is just quoting words from this reference, which is a little clearer that what they mean by "reverberate" is just the light-crossing delay:
"If, as is usually the case, the luminosity varies with time, then the response from the surrounding gas will also vary, but after a time delay due to light-crossing time. This delay or reverberation lag ranges from milliseconds to many hours for irradiation of the innermost accretion flow at a few gravitational radii ..."
Ref: https://link.springer.com/arti... [springer.com]
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Light from the far side of the black hole (Score:4, Informative)
It's not so much that they capture xrays from behind the black hole, the first proof of general relativity was about light bending round the sun and even that did not show that it bends, it showed that it bends twice as much as you'd expect in newtonian gravity. So a gravitational lense could have been imagined even by Newton.
The new thing appears to be - if i get it right- that they are capturing light created at the other side of the black hole, so it resembles more getting glimpses of the far side of the moon.It's the magnitude of the bending which makes the observation cute.
Pink Floyd need to come out of retirement... (Score:2)
Strange? (Score:2)
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.
For crying out loud, how strange is this discovery when it was theorized a hundred years ago and even featured in movies like interstellar?
It is an expected discovery.
Misleading headline and description. (Score:5, Insightful)
This is the most important sentence in TFA (boldface added):
The point here is that the X-ray flares were emitted on "our" side of the hole -- and then echoes appeared that were identifiable as echoes. The X-rays had traveled around the hole one or several times before escaping in our direction.
This is not just "lensing" of light from the far side of the hole a long ways off. This is "reflection".
Einstein's prediciton (Score:3)
I don't believe Einstein predicted anything involving black holes. He did, however, predict that light could be bent by a strong gravitational field. This was demonstrated, if memory serves, during an eclipse many decades ago.
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Article is, of course, super simplified and sensational.
None of this is a surprise, nor in general new.
See also "Einstein Rings"
https://www.google.com/search?... [google.com]
Foresight? (Score:2)
"Fifty years ago, when astrophysicists starting speculating about how the magnetic field might behave close to a black hole, they had no idea that one day we might have the techniques to observe this directly and see Einstein's general theory of relativity in action," said Roger Blandford
Really? So, astrophysicists 50 years ago thought that science was pretty much over?
A really good way to ultimately be proved wrong is to say "x will never be possible", and I'm sure few - if any - of them said or thought any such thing.