The entire history of a star, from a drifting nebula to its final fate, is dominated by the concept of hydrostatic equilibrium. In an essay of 500-600 words, document the state of equilibrium of a massive star, from a nebula at the beginning of the story to a neutron star at the end. When in the star's evolution is it in equilibrium, and when is it not? (Hint: the drifting nebula is in a state of hydrostatic equilibrium before it begins to collapse.)