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Thread: M87 Black Hole is blurry

  1. #1
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    M87 Black Hole is blurry

    https://cdn.cnn.com/cnnnext/dam/asse...xlarge-169.jpg

    The polarized picture of the M87 is magnificent. Any guesses why some parts are so blurry while others are not?
    I know that I know nothing, so I question everything. - Socrates/Descartes

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    Quote Originally Posted by DaCaptain View Post
    https://cdn.cnn.com/cnnnext/dam/asse...xlarge-169.jpg

    The polarized picture of the M87 is magnificent. Any guesses why some parts are so blurry while others are not?
    The black hole is the black hole. The bright parts are probably assorted superheated junk falling into the event horizon. The peculiar bright lines may be an artifact of the processing. Others may know more.

    Hey, thanks, it's a nice image.

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    The peculiar bright lines are the object of the exercise:
    This image shows the polarised view of the black hole in M87. The lines mark the orientation of polarisation, which is related to the magnetic field around the shadow of the black hole.
    The blurry areas have no lines because they have no polarization. See the original Astrophysical Journal article here.

    Grant Hutchison

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    Quote Originally Posted by John Mendenhall View Post
    The black hole is the black hole. The bright parts are probably assorted superheated junk falling into the event horizon. The peculiar bright lines may be an artifact of the processing. Others may know more.

    Hey, thanks, it's a nice image.
    One thing i find confusing is how all this super heated stuff circling the black hole turns into something that’s near absolute zero when it finally becomes part of the black hole. At least that’s what the current model for a black hole states. I don’t see how that material could cool off if there’s no way for the heat to escape.
    I know that I know nothing, so I question everything. - Socrates/Descartes

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    Quote Originally Posted by DaCaptain View Post
    One thing i find confusing is how all this super heated stuff circling the black hole turns into something that’s near absolute zero when it finally becomes part of the black hole. At least that’s what the current model for a black hole states. I don’t see how that material could cool off if there’s no way for the heat to escape.
    That's the point. There's no way for the heat to escape. Matter falling into the black hole doesn't cool off--its thermal energy merely adds to the mass-energy of the black hole and makes the event horizon bigger.

    Grant Hutchison

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    Quote Originally Posted by grant hutchison View Post
    That's the point. There's no way for the heat to escape. Matter falling into the black hole doesn't cool off--its thermal energy merely adds to the mass-energy of the black hole and makes the event horizon bigger.

    Grant Hutchison
    So why is it that science claims that black holes temp is very close to absolute zero? It doesn’t have a temperature? Heat can’t radiate from a black hole? Nothing can escape? Except Hawking radiation.
    I know that I know nothing, so I question everything. - Socrates/Descartes

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    Quote Originally Posted by DaCaptain View Post
    So why is it that science claims that black holes temp is very close to absolute zero? It doesn’t have a temperature? Heat can’t radiate from a black hole? Nothing can escape? Except Hawking radiation.
    Heat can't radiate from inside a black hole, because any photons emitted below the event horizon end up at the singularity, not out in space. Classically, that would give black holes a temperature of zero, because they would always absorb and never emit thermal radiation.
    But when we introduce quantum mechanics we get Hawking radiation, produced at the event horizon. It gives the event horizon an effective temperature, because it emits photons in a thermal spectrum. The smaller the black hole, the larger the effective temperature. So very tiny black holes would be very hot indeed, whereas stellar mass black holes are very cold--colder than the cosmic microwave background.

    Grant Hutchison

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    Another couple questions related to this picture. What is our viewpoint with respect to the black hole? It looks like we are looking from above (or below) on center axis of the black hole. Is the accretion disk directly/mostly in the center of the black hole's magnetic equator? Seems like matter should be attracted from any direction.

    Is all the matter within the black hole polarized in a specific direction? It's gravity that governs the black holes actions on matter but how does it's magnetic field line up with the accretion disk?
    Last edited by DaCaptain; 2021-Apr-01 at 12:32 PM.
    I know that I know nothing, so I question everything. - Socrates/Descartes

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    We have a slanting view of the accretion disc, at about 45 degrees. The impression that you're looking down along the axis is due to the bending of light around the black hole. Take a look at the animations and explanations here for more about that.

    Matter is attracted from all directions, but settles into an equatorial plane for the same reason that planetary rings do--orbital precession results in collisions and gravitational interactions that convert the initially randomly orientated orbits into concentric equatorial orbits.

    The magnetic field is generated by the accretion disc.

    Grant Hutchison

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    Quote Originally Posted by grant hutchison View Post
    We have a slanting view of the accretion disc, at about 45 degrees. The impression that you're looking down along the axis is due to the bending of light around the black hole. Take a look at the animations and explanations here for more about that.

    Matter is attracted from all directions, but settles into an equatorial plane for the same reason that planetary rings do--orbital precession results in collisions and gravitational interactions that convert the initially randomly orientated orbits into concentric equatorial orbits.

    The magnetic field is generated by the accretion disc.

    Grant Hutchison
    You would think that that matter inside the black hole would be magnetically aligned by the magnetic field created by the accretion disk.
    I know that I know nothing, so I question everything. - Socrates/Descartes

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    Quote Originally Posted by DaCaptain View Post
    You would think that that matter inside the black hole would be magnetically aligned by the magnetic field created by the accretion disk.
    A black hole doesn't have that much internal structure. The only way for it to have a magnetic field is for it to be both electrically charged and rotating (a Kerr-Newman black hole). But an electrically charged black hole wouldn't stay charged for long at the centre of an accretion disc, because it would preferentially absorb matter with the opposite electric charge.

    Grant Hutchison

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    Quote Originally Posted by grant hutchison View Post
    A black hole doesn't have that much internal structure. The only way for it to have a magnetic field is for it to be both electrically charged and rotating (a Kerr-Newman black hole). But an electrically charged black hole wouldn't stay charged for long at the centre of an accretion disc, because it would preferentially absorb matter with the opposite electric charge.
    Another way to come at this is to consider that, if a magnetic object inside the event horizon could affect something outside the event horizon, we would in principle be able to send a signal out of the black hole.
    I don't know nearly enough general relativity to say exactly why an astronaut with a magnet couldn't fall through the event horizon and then waggle it around to signal someone else with a magnet on the outside, but I'd bet it has to do with the fact that there's a switch in timelike and spacelike dimensions as you cross the horizon--the infaller is moving away from the external observer both faster than light and in a direction with unusual properties.
    Anyway ... the result is that, for an outside observer, any electrically charged material that falls into a black hole leaves its electric field behind, coupled to the event horizon. If the hole is rotating, the electric field rotates and generates a magnetic field--but those fields don't tell us anything about the behaviour of matter inside the horizon, which is decoupled from the outside world.
    And, in the real world, black holes are exceedingly unlikely to develop and maintain an electric charge, for the reason I gave above.

    Grant Hutchison

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