Cepheid Variable

An unstable star that pulses in and out, causing a periodic change in brightness. In 1912, Henrietta Leavitt discovered what is known as the period-luminosity relationship for Cepheid variables, by which the period of the brightness change is related to the luminosity, and therefore the distance, of the star. An astronomer can plot a Cepheid's changing brightness to create a light curve for the star. The distance to the Cepheid variable is then obtained by measuring the period of the light curve, which shows the length of each pulsation.