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How new stars are borne

  1. Feb 26, 2008 #1
    Why are some stars larger than others? It is my understanding that hydrogen collapses due to gravity into a sphere and when a critical mass is achieved nuclear fusion occurs. Since the critical mass for this to happen is a constant shouldn't all stars be relatively the same size since a star doesn't collect any more mass once fusion starts?
  2. jcsd
  3. Feb 26, 2008 #2
    I don't think this part is true. Why would a star stop collecting mass just because fusion started?
  4. Feb 27, 2008 #3
    The force of matter being ejected by Sol would stop any new hydrogen from being collected. The same reason why Mercury has no atmosphere or what would happen to earth's atmosphere if Sol turns into a red giant.
  5. Feb 27, 2008 #4
    Hmmm. Well, I'm not an astrophysicist or a physicist of any kind, but my thoughts would be: is this true of all stars or just Sol-like ones? Is it really omnidirectional so that mass can't approach from any direction? And would this be true independent of the astrophysical environment, like would it still happen within a dense dust cloud? And does it really happen immediately as soon as fusion starts, or is there a gap in time between fusion and repellent force, during which the inflow of matter from the astrophysical environment will determine the eventual mass of the star?

    It also seems like the velocity of the mass would make a difference. Perhaps if the star forms within a large-scale current or flow of matter the force of that “wind” can inject more mass than in a more tranquil environment.
  6. Mar 2, 2008 #5
    well I guess either no one knows or my question was so incredibly stupid no one could be bothered to answer it. Thanks to those that did post replys.
  7. Mar 2, 2008 #6
    Last edited by a moderator: Apr 23, 2017
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