What causes a supernova, anyway?
The Sun, like all stars, is a vast mass of hydrogen gas which collapsed under its own gravity. As more hydrogen gathered around the central point, the heat at the core of the ball of gas rose to the point where nuclear fusion began to occur spontaneously. Each time hydrogen nuclei (protons) fuse into heavier nuclei, a little energy is released, raising the temperature nearby and enabling further fusion to occur. Thus, the fusion process is self-sustaining for as long as there is enough hydrogen fuel. Stars are generally in hydrostatic equilibrium. This means that the radiation pressure of energy trying to escape from the core (where it was produced by fusion) is equal to the gravitational force pulling the star together. When, after millions or billions of years, the hydrogen fuel begins to run out, fusion slows down and the radiation pressure decreases. Gravity takes over and pulls the star into a smaller ball. This increases the pressure and temperature at the core, to the point wher
