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Space Science

A Black Hole's Spinning Heart of Darkness 121

sciencehabit writes "Like all invisible things that are only partly understood, black holes evoke a sense of mystery. Astronomers know that the tremendous gravitational pull of a black hole sucks matter in, and that the material falling in causes powerful jets of particles to shoot out of the hole at nearly the speed of light. But how exactly this phenomenon occurs remains a matter of conjecture, because astronomers have never quite managed to observe the details – until now. Astrophysicists have taken the closest look to date at the region where matter swirls around a black hole. By measuring the size of the base of a jet shooting out of the supermassive black hole at the center of the M87 galaxy (abstract), the researchers conclude that the black hole must be spinning and that the material orbiting must also be swirling in the same direction. Some of the material from this orbiting 'accretion disk' is also falling into the black hole, like water swirling down a drain."
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A Black Hole's Spinning Heart of Darkness

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  • by MRe_nl ( 306212 ) on Saturday September 29, 2012 @04:40PM (#41501347)

    Vacuum fluctuations cause a particle-antiparticle pair to appear close to the event horizon of a black hole. One of the pair falls into the black hole whilst the other escapes. In order to preserve total energy, the particle that fell into the black hole must have had a negative energy (with respect to an observer far away from the black hole). By this process, the black hole loses mass, and, to an outside observer, it would appear that the black hole has just emitted a particle. []

  • Re:Fascinating (Score:5, Informative)

    by Baloroth ( 2370816 ) on Saturday September 29, 2012 @04:55PM (#41501445)

    It isn't really physically possible (at least, not so far as we know) for a black hole to be considered as a solid physical body. You see, the event horizon isn't the only place where the gravity prevents matter from escaping. Gravity increases until you hit the "outer" part of any body, which means if we assume for a second the event horizon occurs outside all the matter of the former star (which it does), gravity will be slightly more intense inside the horizon. That means that as you travel into the black hole until you reach the outer limit of the physical object itself, gravity will still increase and retain the property of inescapability. What that means is the outer shell of matter can't interact with everything inside, so the normal pressure from electromagnetic and nuclear forces can't keep the outer shell from collapsing inwards (the force literally can't push outwards, since gravity pulls it back).

    That means the outer layer of matter will always collapse inwards, closer to the center, and as that happens, the body becomes more dense and the place where gravity forms a horizon extends ever closer to the center of the black hole. Normally, gravity would decrease after you entered the physical body, so near the center of the black hole there should still be a solid physical body where gravity is less than that required to form a horizon, but as the outer layer of the black hole continually falls downwards (it literally can't do anything else), the space near the center where the black hole retains normal physical properties of a star should diminish to nothing.

    Another fascinating thing is that at the very center, there should be no gravity at all, by the simple rule of symmetry. But the black hole is ever shrinking towards that spot, so that the density approaches infinity and the entire matter of the star becomes condensed into a point with infinite gravitational force. So the center should also end up with infinity gravity. Which is impossible, or should be. That's why black holes are and always will remain a huge mystery, barring some incredible new scientific revelation that overturns the entire theory of... well, nearly everything.

    In other words, for black holes to be treated as solid physical objects, a new force that defies the theory of general relativity (it would have to travel faster than light to allow the matter towards the center of the hole to interact with the matter towards the outer part of the hole) would need to be discovered. And that seems unlikely, although not impossible by any means.

  • by fa2k ( 881632 ) <.pmbjornstad. .at.> on Saturday September 29, 2012 @05:24PM (#41501623)

    Both the replies are correct, but the AC is more relevant. We can't measure the Hawking radiation from particle-antiparticle production and it most certainly doesn't come out in a jet. The article is behind a paywall, but I think they concluded that the black hole itself was spinning based on the gravitational effect on the jet. The distortion of spacetime is different for a spinning black hole and a stationary one.

  • Re:Fascinating (Score:2, Informative)

    by Anonymous Coward on Saturday September 29, 2012 @06:27PM (#41501987)

    Today's black holes allow for âoeevaporationâ and the making of âoejetsâ.

    Jets aren't really escaping the black hole, that matter never actually fell in. And if by evaporation you mean Hawking radiation, those particles were never inside the black hole either, but they do steal energy, but not information.

  • by Anonymous Coward on Saturday September 29, 2012 @10:20PM (#41503269)

    Actually yes, all the time. In many cases, the relevant quantity is change in energy and not absolute value of energy. Hence, where you set the zero point is arbitrary and usually chosen some place to just simplify the math (instead of carrying some junk around that you can demonstrate will disappear when you calculate a measurable value). For example, it is pretty common to treat the zero point at infinity, and so any bound system will be consider negative energy. For an example, an electron being captured by an ion goes from zero energy far away from the ion to releasing energy when captured, hence the electron is at negative energy. It is a matter of bookkeeping, not some deep statement of how the world works in the end.

    Additionally, another example that is also relevant is how some solutions to an equation that gave negative energy ultimately lead to the prediction of antimatter. In the end that negative sign didn't mean much, as they still act just like regular matter, and it only was relevant in interactions between the two.

    Both of those cases are relevant to Hawking radiation, and both of those have observational backing.

  • Re:Fascinating (Score:2, Informative)

    by Anonymous Coward on Sunday September 30, 2012 @01:44AM (#41504045)

    The beliefs of “gravity only” cosmology are founded almost exclusively on computer modeling. Some parts of the electric universe theory can be verified experimentally right here on earth in the laboratory. In the electric universe model, electricity and gravity work together to explain observations without resorting to computerized fiction.

    And out comes the part about astrophysicist ignoring electromagnetism. This is the part of electric universe fans that really grinds my gears and clearly suggests they have never actually looked into any astrophysics research. It is as naive as trying to claim astronomers have never looked at or thought about stars.

    And I don't think you know what a computer model actually does, especially in the fields of astronomy or physics. Those computer models are just solving equations that cannot be solved analytically... just like computer models used to solve Maxwell's equations when you are not dealing with a perfect box/sphere/cylinder. Since the universe is not filled with stuff in the shape of one of the simple cases allowing analytic solutions to Maxwell's equations, MHD, etc., the electric universe theories would have to resort to computer models to check the equations produce the same results on scales larger than Earth (or a laboratory that is the same size or larger than the universe...).

    In the electric universe model, electricity and gravity work together to explain observations

    And welcome to astrophysics, which uses electromagnetism and gravity (along with plasma and particle physics) to explain observation... to explain a metric fuck ton of observation. To imply what you describe as different from mainstream astrophysics is either disingenuous, or completely ignorant of what astrophysics does.

It is not for me to attempt to fathom the inscrutable workings of Providence. -- The Earl of Birkenhead