Transcript: Producing heavy elements by the fusion process requires extreme temperatures. This is because of the electrical force of repulsion that operates between protons. Forcing two protons to combine is four times easier than forcing two helium nuclei to combine, and so on up the fusion chain higher and higher temperatures are required to make heavy elements. In low mass stars, less than about one and a half times the mass of the Sun, the temperature in the core never exceeds the temperature required to produce elements heavier than carbon, and so the fusion process stops with carbon. That’s essential because carbon is a life element, and when it reemerges in the interstellar medium it can seed the formation of planets and eventually life. But for most stars in the universe carbon is the end point of the fusion chain.