The Vogt-Russell Theorem is the proposition that a star's structure and evolution depends only on its mass and chemical makeup. Despite the term "theorem", it is not "proved" as would be a mathematical theorem. However, it is accepted as generally correct for Main Sequence Stars in Hydrostatic Equilibrium, based on observation and current understanding of the structure of stars. http://wwwmpa.mpa-garching.mpg.de/~weiss/Cox_Vol_II_CD/ch18.pdf |