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Main sequence lifetime problem

  1. Oct 26, 2009 #1
    The question states that
    We have a globular cluster with total mass 10^6 times sun's mass.
    Assume that the main sequence lifetime of a solar mass star is 10 gigayear, and a main sequence lifetime scales with mass as M^-2. What is the mass of the most massive main sequence stars in the cluster after 1 gigayear? (answer - 3.2 times sun's mass)

    we have t ~ M^-2

    Does this require me to do a differential and find out the maxima (of the mass) by putting it to zero?
    or by cutting of the massive stars which would die out within the 1 gigayear and somehow see the masses left.
  2. jcsd
  3. Oct 26, 2009 #2
    1) Hint 1: The cluster mass is extraneous information that you can ignore.......

    (stop reading before you get to hint 2)

    2) Hint 2: set it up like a ratio problem.
  4. Oct 26, 2009 #3

    T/t = M/m

    where t = 10 gy and T = 1 gy and
    m = 1 solar mass

    is this correct?

  5. Oct 27, 2009 #4
    Close. What you've set up is the equation for T proportional to M. You are looking for T proportional to M**-2
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