(proposition that a star's structure depends on its mass and makeup)
The Vogt-Russell theorem is the proposition that a star's
structure and evolution (its structure over time)
depend 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 typically
approximately true for main sequence stars in
hydrostatic equilibrium, based on observation and current
understanding of stellar structure. The "theorem" was devised when the
mechanics of binary stars revealed stellar masses, which could
be compared with spectrography and determinations of their
luminosity. Among the confounding factors are the effects of
interactions with companion stars, such as mass transfer (e.g.,
Algol).