ABSTRACT
The internal structure of stars cannot be probed by direct observations. We observe only the radiation emitted by the surface, which allows us to deduce the surface properties. The internal structure must be deduced indirectly by theoretical modeling. Stars are essentially gaseous structures held together by gravitational force. The outward force exerted by the gas pressure balances the inward gravitational pull to maintain equilibrium. The outward pressure is maintained by the heat generated by nuclear reactions in the core of a star.
