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Homework Help: Estimating Central pressure in Star

  1. Sep 20, 2009 #1
    I have a question in an assignment that says "Estimate the central pressure of 0.5, 1.0, and50 solar mass stars. Compare these pressures to the central pressure of the sun"

    I can estimate for the sun using the Hydrostatic equilibrium equation:

    dP/dr = -GM(r)p(r)/R^2

    since I know Mass of sun is 1 solar mass and I know the radius. However, when I want to calclulate the central pressure of the other solar mass stars.. I don't know the radius.. So is there a way for coming up with that? The assignment doesn't give me any more information. Should I assume the same radius as the sun?
  2. jcsd
  3. Sep 20, 2009 #2
    Here's my guess:

    Use the scaling relation between stellar mass and radius:
    [tex] R \propto M^{\frac{n-1}{n+3}}[/tex]
    Where n is the exponent describing how the nuclear energy output scales with the core temperature: [itex]F \propto T^n[/itex].

    (n=16 for CNO-cycle hydrogen burning. n=4 approximates hydrogen burning by p-p chain.)
  4. Sep 20, 2009 #3
    maybe they just want you to use the same radius as our sun and compare the results.
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