Fusion is the process of joining light nuclei together (typically hydrogen-like nuclei). Energy is released since the larger nuclei once more require less energy to keep it together. This is what occurs in the Sun and stars, and tokamaks and stellarators are being used in studies to learn how to harness fusion energy on Earth.
In stars, lighter elements are fused to release energy together with the mass that is constantly present. For instance, of the mass is lost during the fusion of two hydrogen atoms to create helium in the form of electromagnetic radiation or the kinetic energy of an alpha particle.
The transformation of mass m into energy is described by Einstein's well-known equation. On the other hand, when we exert effort on anything, we supply energy, increasing its mass by a factor . (The sign , which is pronounced "delta," stands for "the change in").
Hence, when two small-nucleus elements, like helium and hydrogen, combine, a lot of energy is released. Less energy is generated during the fusion process when heavier atoms are involved. Energy is released during the fusion process up to the element iron , beyond which no energy is released. For larger atoms to fuse, energy is required.
