So stars are born, they live, and they die. Large stars die in a supernova. And that’s it.
Except that it isn’t. Scientists have found a star that has had multiple supernovas. One in 1954, the other in 1993. This is impossible given our current understanding of how stars work. Which means that we need to change our understanding. Our current theories are wrong and need to be changed. This is the exciting part of science, when our understanding has to change to fit the facts.