All stars, including the Sun, have a finite lifetime. Stars shine by the process of nuclear fusion in which lighter atoms, such as hydrogen, fuse together to create heavier ones. This process releases vast quantities of energy which counteracts the ever-present inward pull of the star’s gravity. Ultimately, fusion helps stars to resist gravitational collapse.
This balance of forces is called “hydrostatic equilibrium”. However, there will come a time when the supply of fuel in the core of a star starts to run out and it eventually dies. Stars with more than about eight times the mass of the Sun will typically burn through their fuel in less than 100 million years. Once fusion ceases, the star collapses – generating a massive instantaneous final burst of nuclear fusion which causes the star to explode as a supernova.
