Stellar equilibrium and structure from a simple approach: the Main Sequence

Abstract The simultaneous occurrence of Virial and hydrostatic equilibrium determine the existence of solutions for the simplest stellar models. Using these concepts we show how it is possible to characterize the stellar structure without having to integrate the relevant differential equations, at least to obtain global properties. Later we discuss how the stars generate energy. emphasizing the fundamental role of the weak decay of protons controlling the star lifetime, precluding their explosions in a fraction of a second, thus putting weak interactions on an integrated and more apparent context for the students and teachers. Because its generality and simplicity, this approach is particularly useful for the discussion in the Middle/High School.