The Death of Stars Stars do not simply disappear in death. In their deaths they join in as much in the life-cycle of the galaxy as they did during their prime. In their demise lies the seeds of the next generation of stars and planets. On their way to death stars go through stages that are clear signals of impending disaster. One of these phases are the periodic oscillations of a star.
All stars have variable brightness at some level.
But some stars change their brightness to an extent that is obvious even from large distances. A subset of these stars vary their brightness over constant time intervals. These stars are called periodic variables. Some of these are binary stars but others are stars genuinely changing their brightness over time. The first such stars discovered were the cepheids, recognized to be periodic variables by Henrietta Leavitt.