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Black holes shouldn't echo, but this one might. Score 1 for Stephen Hawking?

Black holes are infinitely dense objects surrounded by smooth event horizons.
Black holes are infinitely dense objects surrounded by smooth event horizons.
(Image: © Shutterstock)

When two neutron stars slammed together far off in space, they created a powerful shaking in the universe — gravitational waves that scientists detected on Earth in 2017. Now, sifting through those gravitational wave recordings, a pair of physicists think they've found evidence of a black hole that would violate the neat model drawn from Albert Einstein's theory of general relativity.

In general relativity, black holes are simple objects: infinitely compressed singularities, or points of matter, surrounded by smooth event horizons through which no light, energy or matter can escape. Until now, every bit of data we've gleaned from black holes has supported this model. 

But in the 1970s, Stephen Hawking wrote a series of papers suggesting that the borders of black holes aren't quite so smooth. Instead, they blur thanks to a series of effects linked to quantum mechanics that allow "Hawking radiation" to escape. In the years since, a number of alternative black hole models have emerged, where those smooth, perfect event horizons would be replaced with flimsier, fuzzier membranes. More recently, physicists have predicted that this fuzz would be particularly intense around newly formed black holes — substantial enough to reflect gravitational waves, producing an echo in the signal of a black hole's formation. Now, in the aftermath of the neutron star collision, two physicists think they've found that type of echo. They argue that a black hole that formed when the neutron stars merged is ringing like an echoing bell and shattering simple black hole physics.

If the echo is real, then it must be from the fuzz of a quantum black hole, said study co-author Niayesh Afshordi, a physicist at the University of Waterloo in Canada.

Related: The 18 Biggest Unsolved Mysteries in Physics

"In Einstein's theory of relativity, matter can orbit around black holes at large distances but should fall into the black hole close to the event horizon," Afshordi told Live Science.

So, close to the black hole, there shouldn't be any loose material to echo gravitational waves. Even black holes that surround themselves with disks of material should have an empty zone right around their event horizons, he said.

"The time delay we expect (and observe) for our echoes ... can only be explained if some quantum structure sits just outside their event horizons," Afshordi said.

That's a break from usually unshakable predictions of general relativity.

That said, data from existing gravitational wave detectors is noisy, difficult to properly interpret and prone to false positives. A gravitational wave echoing off some quantum fuzz around a black hole would be an entirely new sort of detection. But Afshordi said that in the immediate aftermath of the merger, that fuzz should have been intense enough to reflect gravitational waves so sharply that existing detectors could see it.

Joey Neilsen, an astrophysicist at Villanova University in Pennsylvania who wasn't involved in this paper, said that the result is compelling — particularly because the echoes turned up in more than one gravitational wave detector.

"That's more convincing than combing through data looking for a specific kind of signal and saying, 'aha!' when you find it," Neilsen told Live Science.

Still, he said, he'd need to see more information before he was absolutely convinced that the echoes were real. The paper doesn't account for other gravitational wave detections gathered within about 30 seconds of the reported echoes, Neilsen said.

"Because significance calculations are so sensitive to how you pick and choose your data, I would want to understand all those features more fully before I drew any firm conclusions," he said.

Maximiliano Isi, an astrophysicist at MIT, was skeptical.

"It is not the first claim of this nature coming from this group," he told Live Science.
"Unfortunately, other groups have been unable to reproduce their results, and not for lack of trying."

Isi pointed to a series of papers that failed to find echoes in the same data, one of which, published in June, he described as a "a more sophisticated, statistically robust analysis."

Afshordi said that this new paper of his has the advantage of being far more sensitive than previous work, with more robust models to detect fainter echoes., adding, "the finding that we reported... is the most statistically significant out of the dozen searches [I discussed], as it had the false alarm chance of roughly 2 out of 100,000."

Even if the echo is real, scientists still don't know precisely what sort of exotic astrophysical object produced the phenomenon, Neilsen added.

"What's so interesting about this case is that we don't have any idea what was left after the original merger: Did a black hole form right away, or was there some exotic, short-lived intermediate object?" Neilsen said. "The results here are easiest to make sense of if the remnant is a hypermassive [neutron star] that collapses within a second or so, but the echo presented here isn't convincing to me that that scenario is what actually happened."

It is possible there are echoes in the data, Isi said, which would be enormously significant. He's just not convinced yet.

Regardless of how all the data shakes out, Neilson said, it's clear the result here is pointing at something worth exploring further.

"Astrophysically, we're in uncharted territory, and that's really exciting." he said. The paper was published Nov. 13, 2019, in the Journal of Cosmology and Astroparticle Physics.

Originally published on Live Science.

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  • Aaron Aaron
    When two black holes merge, and presumably when a hole and a condensed object or two condensed objects merge, there must be a period when two or more singularities exist within a single event horizon. That would make the horizon non spherical and presumably radiating. I presume this is the mechanism for the "ring-down" radiation from black hole mergers. Something similar must occur when two condensed but not singular objects merge, and this signal could be the "echo" claimed to be detected in this report. I don't have the math needed to predict the shape of such a signal, and must ask the relevant community for assistance.
    Reply
  • Pmasterton
    Wouldn't the data need to include what the two star masses are doing prior to the collision to measure the intial sound of their effect to the space relative to what's going on inside in their atmosphere and around it. Space is very noise we listen it to it 24/7 for alien life if that's able to move through the vastness of universe and not get sucked into the numerous black holes ornobsorbed by all the material or mass es of objects then it must be bouncing all around out their off them hence should show echoing or the possibilities their of. Take your Bluetooth speaker for example put it in a container with space it find a way to amplify and echo outward where theirs openings to more space. The atoms from the collition may not get destroyed but seperate and reform with other causing a share in formation outside of the vaccum kinda how a mirror does with our visuals when looking upon us making a sound but doesn't produce it. Possibly their is a foreign object or thing producing the now said recorded or remembered or coded noises and sounds just like we write music then play it letting the echo of music one hears in their head to escape into reality and that mimmictry of your mind has to be as peculiar as a simple stuff their trying to say is how the black holes is acting after the choas of the collisions. I mean take Jupiter for example it sounds creapy how does that sound escape it's immensive gravational pull even. Put your blue tooth in a shop vac it still plays and is muffled attachments of different types to the hose make it produce difference and carried sounds of the oringal produced sounds and music. Even more so if change the direction. All things in space move and spin it's not anything like say two cars colliding. They collide grind exploide elements are super heated and conducted etc the series of events I bet microscopically is even more insane Thane a brain scan witch is only way u can see the mind kinda witch I believe is one in the same with space or what we are looking for in the sence of dark matter to be like the paper to the pen in the universe the coding has to be applicable to something or it can't be like you can't hammer a nail in space to hang a picture but planets and I think all Rocky and gas bodies have poles. Bipolism is very predominate in all things all well as medians or the 3 with that u get any combination positive or negative in all 10direction this is because = is off spring the sum of or both all in the same in any equation and the vaiousence are what the variable or letter represent in a formula. Like look a the formulas as a whole if the environment telling you information about one environment but them themselves and you viewing them make up its own. I would really like to know what the considering factors in the past present in future of these expearaments. Zoom in and out what all invited in the spacial environment around them and what was in between the source and the instrument gathering the information. Compare it to a whale or other strange noises echoing in the waters and the vs the echoing of a stomping elephant communicating. Their might be some hidden factors key and formulaization or see something that effect ls relevently as misterous to this but on a smaller scale. The partial colider seems to be of us as well.
    Reply
  • Pmasterton
    Pmasterton said:
    Wouldn't the data need to include what the two star masses are doing prior to the collision to measure the intial sound of their effect to the space relative to what's going on inside in their atmosphere and around it. Space is very noise we listen it to it 24/7 for alien life if that's able to move through the vastness of universe and not get sucked into the numerous black holes ornobsorbed by all the material or mass es of objects then it must be bouncing all around out their off them hence should show echoing or the possibilities their of. Take your Bluetooth speaker for example put it in a container with space it find a way to amplify and echo outward where theirs openings to more space. The atoms from the collition may not get destroyed but seperate and reform with other causing a share in formation outside of the vaccum kinda how a mirror does with our visuals when looking upon us making a sound but doesn't produce it. Possibly their is a foreign object or thing producing the now said recorded or remembered or coded noises and sounds just like we write music then play it letting the echo of music one hears in their head to escape into reality and that mimmictry of your mind has to be as peculiar as a simple stuff their trying to say is how the black holes is acting after the choas of the collisions. I mean take Jupiter for example it sounds creapy how does that sound escape it's immensive gravational pull even. Put your blue tooth in a shop vac it still plays and is muffled attachments of different types to the hose make it produce difference and carried sounds of the oringal produced sounds and music. Even more so if change the direction. All things in space move and spin it's not anything like say two cars colliding. They collide grind exploide elements are super heated and conducted etc the series of events I bet microscopically is even more insane Thane a brain scan witch is only way u can see the mind kinda witch I believe is one in the same with space or what we are looking for in the sence of dark matter to be like the paper to the pen in the universe the coding has to be applicable to something or it can't be like you can't hammer a nail in space to hang a picture but planets and I think all Rocky and gas bodies have poles. Bipolism is very predominate in all things all well as medians or the 3 with that u get any combination positive or negative in all 10direction this is because = is off spring the sum of or both all in the same in any equation and the vaiousence are what the variable or letter represent in a formula. Like look a the formulas as a whole if the environment telling you information about one environment but them themselves and you viewing them make up its own. I would really like to know what the considering factors in the past present in future of these expearaments. Zoom in and out what all invited in the spacial environment around them and what was in between the source and the instrument gathering the information. Compare it to a whale or other strange noises echoing in the waters and the vs the echoing of a stomping elephant communicating. Their might be some hidden factors key and formulaization or see something that effect ls relevently as misterous to this but on a smaller scale. The partial colider seems to be of us as well.
    Oh I wanted to add on to the collision of bodies and how they collide remember outside and inside a lot of them or different consistency of molt rock and cores spinning in different direction I'm not sure if that is taken into consideration or how far out are the masses meatured and by what means? They both have different say area of effects depending on what your measuring like it's heat atmosphere or light bands or fire spouts etc or all combined factor as they move closer the area of effects merger is going to produce new causes and effects prior to and actual collision of material.
    PS dont report me to a physictrist I've already been through that but without someone like me we'd have no universal theorizations or anything some of us have to think up this stuff while the others live their say normal lives and don't think for a second about it in their lifetime. You can't have evens with out odds and vice versa
    Reply
  • dylan king
    we are all going to die!!!!!!!!!!!
    Reply
  • TorbjornLarsson
    The signal is interesting but the false detection rate is much higher than Ligo chooses for events - but of course we are looking at a correlation with such so that may be passable.

    Their own analysis mention the modern black firewall hypothesis among others, which is more appetizing than Hawking's analysis of "fuzz".
    Reply
  • TorbjornLarsson
    Aaron Aaron said:
    When two black holes merge, and presumably when a hole and a condensed object or two condensed objects merge, there must be a period when two or more singularities exist within a single event horizon. That would make the horizon non spherical and presumably radiating. I presume this is the mechanism for the "ring-down" radiation from black hole mergers. Something similar must occur when two condensed but not singular objects merge, and this signal could be the "echo" claimed to be detected in this report. I don't have the math needed to predict the shape of such a signal, and must ask the relevant community for assistance.

    The generic ring down mechanism is located outside the event horizon AFAIK, but seems hard to model - event horizons are global properties (but yeah, so is the coupling near field to free wave of antennas, so YMMV). To get a gravity wave source you need a quadrupole mass energy distribution, but you get that from the merging fields (or potentials, if you want to use those).

    Classically an event horizon is spherical if static, but I assume you are looking for something like this https://phys.org/news/2019-11-numerical-evidence-merger-motss-binary.html ]:

    "In their study, published in Physical Review Letters, they collected observations that could offer exciting new insight into the merger of marginally outer trapped surfaces (MOTSs) in a binary black hole (BBH), a system consisting of two black holes in close orbit around each other.

    "It is an underappreciated fact that event horizons are not really very useful for studying astrophysical properties of black hole mergers," the researchers told Phys.org via email. "What is much more useful are surfaces which go under the boring name of marginally outer trapped surfaces (marginal surfaces or MOTS in short). This uninteresting name hides their importance in understanding black holes.""

    The MOTS is roughly the same as the inner horizon of real (rotating and/or charged) black holes, I think https://en.wikipedia.org/wiki/Trapped_surface , https://en.wikipedia.org/wiki/Reissner–Nordström_metric ]. You can handle them analytically if the black hole was collapsing spherically, which AFAIK is the odd case of gravity systems despite the inner heating - Rayleigh-Taylor instabilities https://en.wikipedia.org/wiki/Rayleigh-Taylor_instabilities ] are overcome.

    There is a video (and it tentatively justifies my MOTS = inner horizon identification).
    Reply
  • TorbjornLarsson
    Pmasterton said:
    without someone like me we'd have no universal theorizations or anything

    That is not how science works. Sure, anything can inspire peer review published theory, but web comments are observably unlikely to do so.

    Better leave science development to the scientists. You take care of yourself.
    Reply
  • Pmasterton
    TorbjornLarsson said:
    That is not how science works. Sure, anything can inspire peer review published theory, but web comments are observably unlikely to do so.

    Better leave science development to the scientists. You take care of yourself.

    In reference to thinking different or questioning really not partially myself or comment. New to this and I don't want to have much content not relavent to an article but if you'd like to chat I'm ok with that. I have some interesting stuff I wrote including my own universe theorizations some stuff on center masses, solarplexis and metamorphosis amongst other theorizations, mathematical calculations,formulizations, and equations. Ancient writings scrolls, symbolism and calligraphy I'm into a lot as well.4 drawer cabinet full of stuff I'm into it all aspects from neuroplasticity neurologly micro organism and their world as well as obviously space and the universe.
    Thanks btw for what it's seems is a concern for my health in your closing statement. I thought at first it was meant as an insult until I remembered my therapist mentioning sentence it was a bad attempt at a joke😂 but seriously it's not a joke and yes I admit I have overindulged in studies expiraments, papers and stuff and it effected my family life and earthly needs ,matters and affairs.
    Reply