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Rebuttle of Black hole arguments

  1. Jan 25, 2008 #1
    Hi, my astronomy teacher want's us to give him some possibilities as to why supermassive black holes cannot form by the merging of two stellar black holes

    Any help would be appreciated,
  2. jcsd
  3. Jan 26, 2008 #2


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    Well one possibility surely is initial conditions. They might scatter off one another and not interact. Only in the case of a head on collision or in the case of a decaying orbit might they intersect.

    The latter case is also a little peculiar. There is a thermal bath of radiation exerting an radially outward push so that may or may not cancel energy loss due to friction. Theres also the question of mass. I mean 2 stellar blackholes aren't even close to the mass range of a supermassive bh.

    Anyway im rather surprised your teacher gave you this question, as its completely nontrivial. Blackhole mergers are a poorly understood area and the subject of very active research. Some people expect there to be some sort of very violent processes going on.
  4. Jan 26, 2008 #3
    Collisions between black holes are about as unlikely as collisions between stars.
  5. Jan 26, 2008 #4
    Thanks, but now i have a few questions as to how a supermassive black hole could have formed really early on in the universe by a sudden imposion of a bunch of gas due to the gravitational attraction at such high speeds. If i poorly explained this, then the guy who thought of this teaches at oxford, and maybe that will help. How could the gas just suddenly glob together and form a supermassive black hole.
  6. Jan 27, 2008 #5
    it could happen
  7. Jan 29, 2008 #6
    Its a valid question. Super massive black holes are at the centers of galaxies and weigh in at a million to a billion times the mass of our sun (or a stellar mass black hole). How these super massive black holes built up over time is an active area of research. I know that in the latest cosmological simulations "seed" black holes that are already quite massive must be placed "by hand" in early galaxies to produce super massive black holes that produce observables like the active galactic nuclei / quasars seen today.

    One idea is primordial black holes were produced during the big bang and had a long time to accrete material. Another is that some of the first generation of stars, which were more massive than stars like our sun due to the low metal content, collapsed directly into black holes. There is a very bimodal pattern in the observed black holes (really big guys at the center of galaxies or little wimpy guys in binary orbits with other stars) leading some to assume that there are different processes that lead to their creation.
  8. Jan 31, 2008 #7
    i have a suitable answer for ur question. just consider the event horizon as the entropy of a system. according to the 2nd law of thermodynamics during the merger of two systems the final entropy of the resultant system is equal or more than the sum entropies of the two merging syatems. similarly the two merging blackholes can form supermassive blackholes which wil have its event horizon equal or more than the sum of two event horizons of the combining blackholes.
  9. Jan 31, 2008 #8
    is there a mass multiplyer in the merging system
    when I asked so time ago
    people here said
    NO black holes do NOT radicaly gain mass in merging
    BUT i THINK MR 'E's laws on near light speed mass increase
    is a bigger clue then the 2nd law of thermodynamics
    and donot think they get that big eatting dust
  10. Jan 31, 2008 #9
    Code (Text):
    i know ur right .there can be a factor of mass multipyer bcoz the final area of the eventhorizon directly varies to its mass. it is given by, e=2gm/c^2 where e is the event horizon.
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