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Supermassive Blackholes

  1. Oct 6, 2008 #1
    So, according to stuff i have read over the past few days (quite interesting stuff out there) there is a "supermassive blackhole" at the center of our universe. what i would actually like to know is if this had the supposed mass it does which if i am correct with my memory was something along the lines of 1.8x10^10 solar masses. now if this was that powerful and heavy why wouldn't everything around it become so unstable that they would also start smaller black holes, which in turn would cause the destruction of our galaxy? I Mean if it is there, and is that heavy wouldn't have at least some effect around it (which would cause it to grow and consume more) It seems like a pretty large black hole for weighing that many solar masses.

    which according to wiki is between .0001 - 10 AU

    but still, you would think that something so dense, and so powerful would do something at least, sooner or later?
     
  2. jcsd
  3. Oct 6, 2008 #2
    1.8x10^10 sol mass I think is thought to be the upper limit for SM BH's. The one at the centre of the Milky Way is more in the region of 3.7x10^6 sol mass with a horizon diameter of about 44 million kms.

    http://en.wikipedia.org/wiki/Sagittarius_A*
     
    Last edited: Oct 6, 2008
  4. Oct 6, 2008 #3
    The only difference between a black hole and any other object with mass is its density. If the Earth became a black hole with a radius of 9mm, our satellites would continue to orbit as if nothing happened (minus any measureable changes in frame dragging). The gravitation 'pull' of black holes still succumb to the inverse square law.
     
  5. Oct 6, 2008 #4
    There is no "center" of our universe.

    Maybe you are thinking of the supermassive black hole at the center of our galaxy? Their presence is common to many galaxies.
     
  6. Oct 6, 2008 #5

    George Jones

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    For orbits sufficiently far from the black hole. There exist bound orbits around black holes that look nothing like the ellipses predicted by an inverse-square law.
     
  7. Oct 6, 2008 #6

    Nabeshin

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    Well, if we are indeed talking about super massive black holes at the centre of galaxies, then orbital velocity is roughly constant as radius increases, no?
    (I think you guys are talking about orbits within a few parsecs anyways, so I'm not sure if this relationship holds on distances that small, I only know about on galactic scales).

    Stuff does fall into the black holes, no doubt, which does cause it to grow in mass. People seem to think, however, that a black hole instantly gobbles up everything at an exponentially increasing rate. For galaxies at our current epoch of the universe, the process is nothing like that.
     
  8. Oct 7, 2008 #7
    If I'm not mistaken, there would be no change to the frame-dragging rate either outside the radius of what the collapsed object used to be. The rate would only increase as you ventured inside the radius, eventually reaching c at the ergosphere edge of the black hole. This would change if the black hole was to grow in mass.
     
    Last edited: Oct 7, 2008
  9. Oct 7, 2008 #8
    That is what i meant ^.^

    makes sense i guess. i understand that there can be black hole sattelites, is there any reason that there are blackholes at the center of the galaxy's? or is it just simply because of the power galaxy's have as they are beginning to form.

    Because from how i understand this, if there is a black hole at the center of the galaxy and it did however begin when the galaxy just had started i mean, i don't know what im trying to explain, i am assuming that the galaxy wasn't formed as a patch of dust and started in some form of explosive power. but, all the dust in this galaxy (however many solar masses our galaxy is as a whole) if it were once packed together, and there is a black hole at the center of the galaxy then couldn't we have been a mass at one time, a single mass like a gigantic sun that once it collapsed it formed a black hole and sent an explosion of the dust outwards to form our galaxy (or am i just restating the big bang theory [I'm sort of confused right now]?) so If i am assuming that I can as well picture a chain reaction of explosions, In example:

    Just how i am picturing possibilities here
    1. Universe is simply a gigantic ball of elements which explodes sending dust everywhere
    2. Gigantic sun's are formed just as if it were a gigantic galaxy are formed by the dust.
    3. over billions of years... finally the suns explode forming the galaxy's
    4. when stars from our galaxy explode could there be mini galaxy's? lol i hope not.

    Because it is true that there are several Galaxy's and they all seem as though they have formed already, which in my opinion is strange except for a few probably that are forming now?

    I hope some of that is answerable, the mystery's of the universe confuse me again...
     
  10. Oct 7, 2008 #9
    Grogerian,

    Check out the following link. PBS aired a documentary about the SMBH in our galaxy. If you have a fast internet connection, you can watch it online. It should answer many of your questions.

    http://www.pbs.org/wgbh/nova/blackhole/program.html
     
  11. Oct 8, 2008 #10
    Thanks :) I'll check it out.

    Edit: :) Thank you again, that answered pretty much everything.

    Edit2: Could that be why our galaxy is a spiral galaxy? our galaxy is moving right --?
     
    Last edited: Oct 8, 2008
  12. Oct 29, 2008 #11
    Our galaxy is a barred spiral galaxy. It being a "normal" spiral galaxy is a common misconception. :) we are loacted near the middle of one of the arms i believe... But our galaxy along with all the other galaxies in the universe are moving. When we look at the 44 galaxies in our local group, they have a blueshift because we are all moving to a common center some where near the middle of our group. But when you look at the rest of the galaxies in the universe, they are redshifted and moving away from us. Everything in the whole universe is moving, even black holes. :)
     
  13. Oct 29, 2008 #12
    Is it fair to assume that the more mass that falls into a Black Hole the smaller, i.e. less dia., its Event Horizon is?
     
  14. Oct 30, 2008 #13

    George Jones

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    No, it's the other way around.
     
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