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Black Hole

  1. Mar 17, 2010 #1
    Since the earth and the sun have a common center of mass in which the sun has its "wobble" thing goin wouldn't that be the same for the black hole in the center when it comes to the galaxy regardless of the mass comprised in such a small area
  2. jcsd
  3. Mar 17, 2010 #2


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    You mean, does the black hole "wobble"? I suppose it could, but I don't know how you would observe such a wobble.
  4. Mar 17, 2010 #3
    Seems like a black hole should wobble according to the greatest nearby gravitional influence....unlikely that would be the center of a galaxy in general, but it could be...

    the biggest black holes seem to be those near the hub of galaxies and those would be incredibly massive (and resistant to wobble) with the one at the center of our galaxy about 100,000 miles across....and the distribution of masses throughout the galaxy might well tend to largely cancel....so the wobble might be small....or not...
  5. Mar 18, 2010 #4


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    What observational consequence would you expect? I perceive it would be very local.
  6. Mar 18, 2010 #5


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    In black hole - neutron star binaries the BH certainly orbits the center of mass of the system. Simply an extreme case of the wobble, but you could concoct some two body system for any black hole where the cm is inside the event horizon. I suppose you could hope to detect the wobbling in the accretion disk in an attempt to verify this motion, but owing to the messy features of these disks I'm not sure how obvious such a wobble would be... But perhaps in a quasi-stable system such as a BH siphoning matter off a white dwarf or red giant, where the accretion disk is relatively stable, such a wobble could be measurable.

    Naty1 is right though, one doesn't expect a wobble with a uniform distribution of mass, so the smbh in the center of the galaxy example is not a good one.
  7. Mar 18, 2010 #6


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    Black holes are very ordinary citizens of the universe until matter wanders in too close. This is part of what bugs me by worries about a microscopic black hole eating earth. A mini black hole can no more consume earth than a minnow can swallow a whale.
  8. Mar 19, 2010 #7
    yeh people need to understand that the black holes in space are results of tons of matter comprised into a small area, not from two atoms smashing into eachother, the mass isn't logically possible to obtain from such an event
  9. Mar 19, 2010 #8
    Could you try to observe the background look what happens to light around the black hole?
  10. Mar 20, 2010 #9
    maybe gravitational waves...
  11. Mar 22, 2010 #10
    The Sun rotates around the barycentre that it shares with all the other orbitting bodies of the solar system, but since the Sun masses more than 1,000 times the heaviest planet, the barycentre is close to the centre of the Sun - Jupiter's mass and distance are just enough to place the barycentre just outside the surface of the Sun, but usually the pull of the other planets pulls it back into the Sun. It's a fictitious point in space where the angular moment of all the planets and the Sun add together, and the Sun's motion around is enough to make Jupiter and possibly Saturn detectable from other star systems.

    What about the Galactic Core, you ask? The black hole there masses ~4.2 million times the mass of the Sun and most of the mass of the Galaxy orbits around it more or less evenly. Thus it would be fairly close to the barycentre of the whole Galaxy, if there's nothing orbitting nearby that's not similarly heavy. There is a very large star cluster near it and that might cause them to orbit outside their mutual barycentre. Why don't you look it up online for the latest details?
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