1. The problem statement, all variables and given/known data Consider a start of mass M and radius R. 1.It can be modeled as a single shell in hydrostatic equilibrium The star's pressure is given by P(core)/2 The star's density is average density a 2.Period=star's diameter/speed 3.Speed=sqrt(γP/a) γ=5/3 P is the average pressure Please deduct a relation between period T and density a, your answer should be T=Ka^(-1/2) where K is a constant you should be able to calculate. 2. Relevant equations hydrostatic equilibrium (Pressure of the surface-Pressure of the core)/Radius = GMa(average density)/Radius^2 so that's ΔP=GMa/R 3. The attempt at a solution I've been trying it for numerous times but just can't get the right answer. I assume that: according to hydrostatic equilibirum rule P(core)/2=(GMa)/R and T=2R/speed = 2R/sqrt((5/4)P/a) since average pressure should be (P/2 + P)/2 So from the first equation, I get that P=(2GMa)/R so plug this into the second equation It's too complicated to put here but I just can't get the right answer.. is any of those steps wrong so I can make corrections?? Thanks a lot!!