AST 2002 Chapter Notes - Chapter 11.2: Photosphere, Photon, Radiation Zone
Document Summary
The sun shines because of energy generated by nuclear fusion, and that this fusion occurs under the extreme temperatures and densities found in the suns core. The nuclear reactions that generate energy in the sun are very different from those used to generate energy human-built nuclear reactions on earth. If nuclei collide with sufficient energy, they can stick together to form a heavier nucleus. The strong force, which binds protons and neutrons together in atomic nuclei, is the only force in nature that can overcome the electromagnetic repulsion between positively charged nuclei: is like a glue or velcro. Pushing the positively charged nuclei close enough together for the strong force to outmuscle the electromagnetic repulsion. The high temperature is most important because the nuclei must collide at very high speeds if they are to come close enough together to fuse: the higher the temperature, the more energetic the collisions are. The high pressure of the overlaying layers is also necessary.
