Nuclear fusion

In nuclear physics, nuclear fusion is a nuclear reaction in which two or more atomic nuclei come very close and then collide at a very high speed and join to form a new nucleus. The mass of this new nucleus is slightly less than the sum of its constituents, by an amount known as the "binding energy". This is because the compound nucleus is a lower-energy system (a "more favourable" system energetically) than the two parent nuclei. The binding energy is released as photons (energy). This is the energy that is given off by a fusion process. Fusion is the process that powers active or "main sequence" stars, or other high magnitude stars.