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Black Holes emitting jets of gas?

  1. May 2, 2010 #1
    While watching the Discover Channel, they mentioned a jet of gas emitting from a black hole . . . . yet they say they are so powerful that not even light can escape them. So if not even light can escape the gravity, how would "jets of gas"?

    As a side note, . . . I realize that most of theoretical physics is based upon the math. My question is, because it works on paper, does that mean that it would really work in reality [such as singularities]?

    Thanks for the input.

    First post. I hope to find some good information on this site.
  2. jcsd
  3. May 2, 2010 #2


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    Nothing can escape from inside the blackhole - or rather from the event horizon - but it's difficult for stuff to actually get into the blackhole.
    Because of angular momentum a disc of material forms in orbit around the blackhole, it's collisions in this which generates a lot of energy, and the magnetic field of the black hole that creates jets.
  4. May 2, 2010 #3
    I see what you're saying. Maybe the Discovery Channel is being a bit too "info 101" with people. They DID talk about quazars being jetted out at extreme rate.
  5. May 2, 2010 #4
    They reran the episode and said that "black holes are messy eaters" and that the gas was due to the black hole riping off the outer layers of a nearby star.
  6. May 3, 2010 #5


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    So, is a magnetic field less affected by the gravity of the black hole that creates it? How is it able to escape this terrific force?
  7. May 3, 2010 #6

    Jonathan Scott

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    A field (gravitational, electric or magnetic) doesn't need to "escape" anything. It is formed as the source material accumulates, before it becomes a black hole.

    In the specific case of a magnetic field, there is an odd feature that a black hole itself cannot have a significant intrinsic magnetic field. This is because according to the well-known "no hair" theorem black holes cannot contain both types of charge, only a single overall value of charge, which cannot be very large otherwise it would prevent any more material of the same charge falling into it, and hence neutralize the excess charge. The intrinsic magnetic field of a black can only be due to its overall charge and angular momentum, and this is tiny compared for example with the magnetic field of a neutron star.

    Experimental evidence suggests strong magnetic fields in the vicinity of quasars and other black hole candidates, and theoretical models of jets suggest that magnetic fields could be involved. As black holes cannot themselves have magnetic fields, this suggests that the field must somehow be due to material in the accretion disks around the central object, but there is some experimental evidence of strong fields in the vicinity of the central object itself, which would conflict with the black hole model and is hence rather difficult to explain.
  8. May 3, 2010 #7
    Wouldn't the ergosphere and accretion disc act as a massive dynamo? That would make a lot of sense.
  9. May 3, 2010 #8


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    Thank you Jonathan.

    Let's say the accretion disk around the black hole at the centre of our galaxy started accumulating more and more material and this material blew a huge magnetic loop into the rest of the Milky Way galaxy. Do you know if that would affect life as we know it? As I understand it, the black hole at our centre has been somewhat dormant and is due to begin a feeding frenzy once again... around now.
  10. May 3, 2010 #9
    Earth is too far on the edge of a spiral arm to be in any trouble from our galactic core, active or not. We are, 27,000 ly from the center I believe; a terribly long way, and time for anything to have an effect. The jets should not loop, but they should be shot from the poles of the axis of rotation, so we would not be in the way in any case. If such a field recoupled, it would do so well within 27,000 ly. Then, there is a good question: what life will be on Earth in 27,000 years? If we have advanced greatly, we could shield ourselves, or migrate. If, as seems more likely, we are dead, then other life should survive.
  11. May 4, 2010 #10


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    Thanks for the good news IcedEcliptic!
  12. May 4, 2010 #11
    It's my pleasure baywax. :) Lets hear it for being distant from an AGN! hip hip hooray!
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