Anonymous asked: A pagan astrophysics major told me another answer: As it turns out, iron is life to blood, but is death to stars. Elements lighter than iron can release energy with their fusion, but once a star proceeds up the fusion chain to the point of producing iron, it begins gaining deadweight and cooling/losing energy, because iron eats energy in its fusion reaction rather than releasing it. Eventually a star will "choke" on the iron and collapse. Iron comes from the death of a star.