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Super massive black hole

  1. Jul 17, 2006 #1
    Hi, I had a few questions about the super massive black hole.

    1. Are Super Massive Black Hole the nucleus of an active galaxy or in the nuclues?(if in the nuclues, then what else is there? try to be a little explanatory)
    2. I used to know this, what causes extragalactic jet?
    3. I know black holes are created by fusion but I also forgot how fusion works, can someone explain it to me?(I looked up in encyclopedia but didn't work).
    4. How does a black hole die?(I know how it dies; when no more objects are in its gravitic reach but how is that possible?)
    5. There is a sort of stars that change colors really rapidly, the only theory they can come up w/ is that it is a black hole, but how can we see a black hole then?
    Last edited: Jul 17, 2006
  2. jcsd
  3. Jul 17, 2006 #2


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    Hey superweirdo,

    I'm probably not up on the very latest in such research, but I think I can give you the gist:

    1. A black hole all by itself is essentially invisible (except for its gravitational effects on nearby objects). Active galactic nuclei (quasars) are thought to contain black holes which are in the process of gobbling up other matter in galaxy's nucleus. The accretion of matter around the black hole leads to enormous heating and energy output, making the hole visible from a distances of many billions of light-years.

    2. Relativistic jets are probably caused by intense magnetic fields in the accretion disk around a supermassive black hole. The hole's rotation drags the matter (and the magnetic fields) around, making it difficult for these super-hot relativistic particles to escape anywhere but along the poles of the rotation. (I'm sure someone else can provide a less hand-waving account of this phenomenon than I.)

    3. Fusion is what powers normal stars. Black holes exist beyond conditions that would break apart all atoms, even the products of fusion reactions, into a soup of free neutrons. Thus, fusion does not occur inside black holes.

    4. Black holes are not like vacuum cleaners; they do not induce matter to come closer than would any other object of the same mass. In fact, one could orbit a black hole quite easily, in the same way one could orbit any other object, and never fall in. (Of course, the intense radiation and tidal forces might cause you some additional trouble...) Black holes cannot be said to be "dead" just because no matter is actively falling into them. They're just "dormant." Black holes do evaporate, however, via a process known as Hawking radiation. Over time, black holes lose mass through this process, and eventually can disappear entirely. The larger the hole, the slower this progresses, however.

    - Warren
  4. Jul 17, 2006 #3
    Updated/Refined questions
    1. How does hawking radiation works?( I looked it up, but I need a more explanatory version)
    2. I know what relatavistic jets are caused by but how do they manage to escape black hole?
    3. I know fusion doesn't occur inside black hole but it is formed when fusion is done for a massive star. How does Fusion works?( I looked it up but same here)
    4. There is a sort of stars that change colors really rapidly, the only theory they can come up w/ is that it is a black hole, but how can we see a black hole then?
  5. Jul 17, 2006 #4


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    1. Hawking radiation is a process which occurs immediately outside the black hole's event horizon, the mathematical surface which denotes the point of no return. When something crosses the event horizon, it cannot escape.

    The vacuum is actually seething with pairs of particles and antiparticles which come into existence and then annihilate shortly thereafter. This process, occuring just outside the event horizon, can lead to an interesting result. If one of the pair falls into the black hole, yet the other escapes, the ultimate conclusion is that the black hole has actually lost mass. Energetically, it's exactly as if the black hole had "emitted" a particle from immediately outside its own event horizon.

    2. Relativistic jets don't escape the black hole. The matter which composes the jets comes from the accretion disk, which is outside the hole's event horizon. Nothing, once inside the event horizon, can ever escape.

    3. Fusion is the process by which light nuclei like hydrogen are combined to form heavier nuclei like helium. This process occurs under conditions of enormous temperature and pressure.

    4. I don't know what you're talking about. Could you provide a reference?

    (Note that we never see a black hole itself. We see the disc of material, getting close to falling in, which is orbiting the black hole. This disc of material, called the accretion disc, is heated enormously by the black hole's tidal forces. The black hole itself is, of course, black. We can also detect a black hole by observing the motion of other luminous objects orbiting it.)

    - Warren
  6. Jul 17, 2006 #5
    I am talking about quasars; http://en.wikipedia.org/wiki/Quasar
    I am know hydrogen bombs work by fusion too, but fusion is the process of adding, then how come it results in explosion?
  7. Jul 17, 2006 #6


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    When you combine two light nuclei, you get a heavier nucleus, plus some binding energy, released as heat and light and kinetic energy of fast-moving particles. If you fuse enough nuclei simultaneously, you release enough energy to level cities.

    The Sun "generates" energy by fusion, as well. It just happens deep inside an enormous sphere of gas. The bulk of the sun's mass "contains" the fusion reaction and acts as a shield, absorbing nearly all the radiation and subatomic particles violently released by the reaction. The energy is eventually converted to heat energy. The Sun is thus hot, so it glows.

    - Warren
  8. Jul 17, 2006 #7


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    Hydrogen and Helium burning occur in several ways as clearly shown at this site.

    The explosions (most common type) are explained here.
    Last edited: Jul 18, 2006
  9. Jul 17, 2006 #8
    In response to your light changing stars the only thing I can really think of is that the super massive black holes at the center of galaxies are orbited my super massive stars. These stars are up to 100 times the size of our sun. And a number of these may infact be orbiting each and every super massive black hole. I have read that the super massive black hole does not have the gravitational capability to hold an entire galaxy together but rather the combination of the super massive black hole and the multiple super massive stars do.
  10. Jul 22, 2006 #9
    One of you said that black hole dies b/c it starts taking antiparticle and loose mass but what I don't understand is that why would it take one of the antiparticle and don't take its pair partner particle coz if it would, there wouldn't be any diff.
  11. Jul 22, 2006 #10


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    Particles are always created in pairs. To conserve momentum, they are created travelling in different directions. When pair creation happens just outside the event horizon of a black hole, one particle can fall in, while the other, headed in a different direction, can escape.

    - Warren
  12. Jul 25, 2006 #11
    I didn't know pairs are created, I thought they were always there like energy. Wait, so do pairs die or decay too?
  13. Jul 25, 2006 #12


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    That's the whole point of colliders like Tevatron and LHC; you smack a proton into an anti proton just to produce the energy to create pairs of other particles. Google "pair production".

    As for dacaying later, that depends on what kind of particle they are. If they're typical QCD mesons each particle decays very quickly. And that can be the point of the experiment too; there's lots of information in just what and how it decays into. Google on "B-Factory".
  14. Jul 25, 2006 #13
  15. Jul 25, 2006 #14
    I just got a few more questions about supermassive black holes
    1. if black holes evaporate b/c of taking antiparticle, wouldn't they take equal number of particles too b/c of probability? So just b/c it takes antipartical and dies, that doesn't make sense.
    2. Since supermassive black hole is in the center of the galaxy, how is it even possible for other matters to orbit it since anything that comes within its contact gets sucked in?(or is it only true for event horizon?-anything that comes in contact w/ it)
    3. Since inside black hole, space and time folds in itself, it isn't bigger than a few dust particles, is that right?
    4. However, how big is the event horizon? B/c if the event horizon is 100 of miles long, it wouldn't matter if black hole is only as big as a few dust particles.
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