Tags: Star.
BL Herculis variables are a type of variable star with low luminosity and mass that have a period of less than eight days. They are pulsating stars making up a subclass of Type II Cepheids with light curves that frequently show a bump on the descending side for stars of the shortest periods and on the ascending side for longer period stars. Like other Type II Cepheids they are very old population II stars found in the galaxy’s halo and globular clusters.