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Does how black holes inside galaxies orbit around the central black hole tell us

  1. Feb 28, 2012 #1
    Does how black holes inside galaxies orbit around the central black hole tell us anything useful? Could be my noobness, but the idea of a bunch of black holes orbiting a central black hole just seems messy. ha. Have we got the jist of what would happen if a black hole ate another black hole? if another black hole grew larger than the central one in our galaxy? or can we explain most other black hole on black hole interactions??


    Black hole on black hole. New type of fetish.
     
  2. jcsd
  3. Feb 28, 2012 #2
    Re: orbDoes how black holes inside galaxies orbit around the central black hole tell

    The orbital velocity can tell us the sum of the masses of the two black holes. If we already know the mass of one of them and if the masses are not too disparate, we can find the mass of the other.
     
  4. Feb 28, 2012 #3

    DaveC426913

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    Re: orbDoes how black holes inside galaxies orbit around the central black hole tell

    Gravitationally, black holes are no different than any other massive object such as a star. If the sun were replaced with a black hole of similar mass, Earth happily continue orbiting without knowing the difference.

    You could replace each star in the galaxy one by one with a black hole of the same mass and they would continue to orbit as before.
     
  5. Feb 28, 2012 #4
    Re: orbDoes how black holes inside galaxies orbit around the central black hole tell

    Why?

    yes, yes and yes
     
  6. Feb 29, 2012 #5
    Re: orbDoes how black holes inside galaxies orbit around the central black hole tell

    Terrifying picture :).

    But isn't it that the large-scale galaxy structure depends on something more than gravity? I.e. the spiral arms are somehow stabilized by supernova explosions. We can't also deny the solar wind pressure in large scale.
     
  7. Mar 1, 2012 #6
    Re: orbDoes how black holes inside galaxies orbit around the central black hole tell

    source?
    That seems interesting.

    Infinite density doesn't seem nice. Could be my lack of mathematical understanding but if the amount of gravity an object has is dependent on its mass. And density is dependent on mass&volume, then black holes would seem to a layman(atleast this one) to not follow the same rules as stars which do not have infinite density. To me that black holes would tear up the space around them, destroying the structure of the galaxy. In actuallity tho, I guess I am right but only slightly. atleast from my point of view after reading more into black holes, they do effect the space around them. But that effect is crucial to galaxy formation, Not its distruction.(atleast in the sense that I was talking about)
     
    Last edited: Mar 1, 2012
  8. Mar 1, 2012 #7
    Re: orbDoes how black holes inside galaxies orbit around the central black hole tell

    we can't? I thought that stellar wind drops off so steeply due to 1/r2 that compared to the distances between stars, it would be irrelevant. Or at least I've never heard any of my professors bring this up as an important concept, nor have I read of stellar wind pressure being important on galactic scales.

    I may just be wrong though, I'm not a part of the astrophysics community so it is very likely that I could be unaware of that kind of idea.
     
  9. Mar 1, 2012 #8

    DaveC426913

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    Re: orbDoes how black holes inside galaxies orbit around the central black hole tell

    I'm not suggesting literally the galaxy would happily go on about its business indefinitely. All I'm trying to get across is that, from a distance, the gravitational pull of a black hole is no different from that of a star of the same mass. Gravitationally, you can interchange them.
     
  10. Mar 1, 2012 #9
    Re: Does how black holes inside galaxies orbit around the central black hole tell us.

    I knew what you were talking about. Very clarifying, my bad for not saying so sooner
    :)
     
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