Stars are the fundamental observable constituents of the Universe. They are the first objects we see in the night sky, dominate the light produced in our own and other galaxies and nucleosynthesis in stars produces all the elements heavier than helium. A knowledge of stars and their evolution is vital in understanding other astrophysical objects from accreting black holes and galaxies to the Universe itself.The structure of a star can be described mathematically by differential equations which can be derived from the principles of hydrodynamics, electromagnetic theory, thermodynamics, quantum...