1. The problem statement, all variables and given/known data P=Kρ^2 is a solution to the equation of the combination of the Hydrostatic Support equation and the mass continuity equation. Find the radius of the star. 2. Relevant equations ρ(r) = (A / r) sin (root( 2πG/K) r) 3. The attempt at a solution The first part of this was to prove first it was a solution which I have done fairly easily, however the last part about the radius has left me confused. I figured the density at the surface (r=R) was equal to zero therefore: 0=(A / r) sin (root( 2πG/K) r) And for the non trivial solution: sin (root( 2πG/K) r)=0 so root(2πG/K) r)=nπ (for n integer) However this would give a range of radii for the star which doesn't seem right. Can you see what I've done wrong, thanks?