Stellar structure equations

The stellar structure equations describe spherical hydrostatic stars through radial conservation of mass, force balance, energy generation, and energy transport. An equation of state, opacity, energy-generation law, and boundary conditions close the system.

In spherical stellar structure, a shell of radius $r$, thickness $dr$ and mass density $\rho$ has mass $dm=4\pi r^2\rho dr$. Integrating outward gives the enclosed mass, $m(r)=4\pi {\int }_0^r\rho (s)s^{2}ds$.