A solar$-$mass star $($M $=21030$ kg$)$ will eventually $($after all fusion processes have stopped$)$ collapse down into essentially a degenerate electron gas, with a bunch of nuclei mixed in to neutralize the charge and provide the gravitational attraction that holds the star together. We$$ll derive a relationship between the mass of the star and its radius. Amazingly, it$$s a good approximation to treat the star as having T $=0$ as far as the electrons are concerned.