Supernovae: A brief

Stars exist due to a fragile balance, the mass of trillions and trillions of hot plasma is being pulled inwards by gravity, with so much force, that nuclei fuse. Hydrogen fuses into helium, which releases energy, pushing against gravity.

In really massive stars, when the hydrogen runs out, for a split second the balance tips, and gravity wins and squeezes the star tighter than ever. The core burns hotter than ever, fusing heavier elements, while its outsides swell. Carbon burns into neon for centuries, neon burns into oxygen for a year, oxygen fuses into silicon for months, and silicon fuses into iron in a day.

Iron is basically nuclear ash, it has no energy to give, and cannot be fused. Fusion ends here and the star starts collapsing in on itself. Protons and electrons merge and turn into neutrons. These continue to push against each other. Aside from the core, the leftover gases blow out in what we call a Supernova. This is by far the largest known blast of energy in the universe.