By utilizing the Stefan-Boltzmann Law and the basic properties of a sphere's surface area, a star's luminosity, temperature, and radius can be mathematically related and thus used to calculate each other.
From measuring the distances to galaxies to discovering new planets, studying variable stars allows us to refine our current understanding of astrophysics and get to the heart of how our universe works.
Stars can go nova multiple times, and is an accretion-explosion cycle; while supernovas only occur once in a star's lifetime and are caused by a high mass star core collapse, releasing great amounts of energy
High mass stars have a more stable evolution from one fusion process to the next. As iron fills the core, the star begins to implode and fall into itself. There are two types of supernovae, based on the hydrogen content.