Within starry galaxies, astronomers have observed two types of supernovas. When a massive star reaches the end of its lifetime, it loses fuel and some of its mass starts to flow into its core. Eventually, it becomes so heavy that it collapses and explodes into an iron-core collapse supernova. Thermonuclear supernovas, on the other hand, occur when small white dwarf stars run out of matter and begin to siphon matter from another nearby white dwarf star, eventually accumulating so much mass that it explodes into a supernova.
But neither of these supernovae fully explain an event that occurred thousands of years ago. In the summer of 1054, Chinese astronomers recorded a star that radiated so brightly it was visible in daylight and shined for 23 days. The explosion, now known as SN 1054, was a supernova, and its remnants formed the Crab Nebula. In the 1980s, University of Tokyo researchers first theorized that the blast was caused by a third type phenomena called an electron-capture supernova.
