> > You might try a more realistic equation of state.  The one you have is
> > an ideal thermodynamic gas equation with considerations made for heat
> > capacities (gamma = Cp / Cv is the adiabatic index - the ratio of
> > specific heats).  This might be sufficient for gases at densities well
> > below those found at the critical point, but at higher densities, the
> > fluid becomes 'incompressible'.

> > You might try a 'hardened' equation - one which has special
> > considerations for high pressures, in which drho/dP is less variable
> > at higher pressures.

> This is wrong - stars like the Sun are nearly ideal throughout, though
> with varying heat capacity in the ionisation zones. The deviation from
> ideality that does occur in stars at high density is well modeled by
> electron degeneracy pressure.

> Andrew Usher