1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Stellar structure of stars problem

  1. Mar 4, 2014 #1
    1. The problem statement, all variables and given/known data
    Consider a star of radius R, with density p that is constant, composed of classical, nonrelativistic, idealg gas of fully ionized hydrogen.
    a. Solve the equations of stellar structure for the pressure profile, P(r) with the boundary condition P(R)=0
    b. Find the temperature profile T(r)
    c. Assume that the nuclear energy production rate depends on temperature as E==T^4. At what radius does E decrease to 0.1 of its central value, and what fraction of the star's volume is included within this radius?

    2. Relevant equations
    A) dP(r)=-G*M(r)*ρ(r)*dr/r^2
    B)dT(r)/dr = -3/4 *( L(r)*k(r)*ρ(r))/(4∏r^24acT(r)^3)
    C) I'm not sure about the formulas for C

    3. The attempt at a solution
    I think I get A part. You have to integrate from r to R of
    dP(r)=-G*M(r)*ρ*dr/r^2 ;ρ= M(r)/(4/3)∏r^3, solve for M(r)
    =-G*ρ^2*(4/3)*∏*integration of r

    b part: I have no idea. Which values will be constant and why?

    c part: I'm also not sure which equations to use

    Please help and explain thoroughly or set me on the right track! Also please explain the concepts too! Thanks
  2. jcsd
  3. Mar 4, 2014 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    For part c, you have to solve part b and figure out the radial distribution of temperature within the star.
  4. Mar 4, 2014 #3
    any idea on part b?
  5. Mar 4, 2014 #4


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    You've got a first order ODE to solve here. It's not clear what functions L(r) and k(r) are and how they vary with r, nor what boundary conditions to apply.
  6. Mar 4, 2014 #5
    Yeah, that's what I'm trying to figure out. Would the luminosity be constant in this case? or would I need another equation to substitute it with?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted