Celestial Bodies such as stars can produce light. This is done by a process called nucleosynthesis. Basically, protons in the star's core are fusioned into Helium in the star's core, releasing energy in the form of a photon (light particle which carries the electromagnetic force), a neutrino, and a positron (an antielectron- a unit of antimatter). Countless billions of photons are generated in the star's core each second, thus creating light from a star.