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Thread: "Active Galaxies"

  1. #1 "Active Galaxies" 
    Forum Senior bill alsept's Avatar
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    Jul 2012
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    I am very interested in gravity and many of the articles I have read end up discussing galaxies. When it comes to the subject of active galaxies depending on what article you read the cause is not always clear. Some articles tend to discuss this activity as turning on and off as in the black hole turning on and off or something that the hole itself is doing. I can understand the activity starting and stopping based on materials in the galaxy spiraling into the hole. If too much material is pushed toward the black hole at one time it would bottleneck and be pushed out before it ever gets to the hole (causing this actively). Then at all other times the black hole would just be fed smoothly as a consistent amount of matter slowly spirals into the black hole (this being considered an inactive period). I'm not sure if I'm asking this question correctly but how do you guys interpret the cause of the starting and stopping?

    Last edited by bill alsept; December 26th, 2012 at 03:02 AM.
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  3. #2  
    Quagma SpeedFreek's Avatar
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    Jan 2011
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    I interpret it pretty much exactly as you described - a galaxy is active when its central black hole is "feeding".

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  4. #3  
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    No one knows exactly how this process works. To elaborate on your good description, matter spiraling into the super massive black hole (SMBH) creates an accretion disk. Matter in the disk moves so fast that the protons are stripped of their electrons by friction. The spinning SMBH acts like a dynamo and generates an enormous electromagnetic force. As the matter in the accretion disk reaches the point of no return, only a finite amount can pass this point. The rest gets split off into two opposing jets at the magnetic poles of the SMBH. To clarify, this is not matter escaping the SMBH because it had not crossed the event horizon. So you get an active galactic nuclei (AGN) with two jets.
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  5. #4  
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    Quote Originally Posted by SpeedFreek View Post
    I interpret it pretty much exactly as you described - a galaxy is active when its central black hole is "feeding".
    Sounds right! Hawking thinks black holes were created by the Big Bang.
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  6. #5  
    Forum Ph.D. merumario's Avatar
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    Nov 2012
    Hawkings said if the theory of general relativity is right,then there must have being a singularity at the early universe.
    "I am sorry for making this letter longer than usual.I actually lacked the time to make it shorter."###
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