Fusion Energy A fusion reaction is one in which two atomic nuclei merge to form a heavier nucleus. this is the process that happens in in the stars. In average stars, like the sun, the process of fusion is converting hydrogen nuclei (or protons) into helium nuclei. There is an enormous amount of kinetic energy and gamma rays released in this process that heat the star's interior, and this realease is what maintains it at the extreamly high temperatures (greater than 10 million K) required to continue the fusion. This process has been making the stars go for billions of years has clear potential as a power source on earth. Once we have started the reaction,