Period-Luminosity Relation



  • Link between the absolute magnitude of a Cepheid variable and the period of its light curve, discovered by Henrietta Leavitt. She found that brighter Cepheids have longer periods, in a mathematically precise fashion, so that as soon as a Cepheid’s period and apparent magnitude are known, its distance can be worked out simply. This is the key to the determination of all stellar distances beyond the small range of parallax measurements.