(variable star): a type of variable star that changes brightness by changing size and temperature with a period that depends on its average luminosity. More luminous Cepheids have longer pulsation periods. Cepheids are particularly valuable for determining distances to the nearby galaxies in which they reside. Distances to Cepheids are derived from measurements of their pulsation periods and apparent brightnesses and application of the inverse square law of light brightness.

a star orbited by a planet

a variable star whose intrinsic brightness is related to the period of its oscillations

A pulsating variable star. This type of star undergoes a rhythmic pulsation as indicated by its regular pattern of changing brightness as a function of time. The period of pulsation has been demonstrated to be directly related to a Cepheid's intrinsic brightness making observations of these stars one of the most powerful tools for determining distance known to modern day astronomy. The existence of of this period-luminosity relationship was a point of contention during the 1920 Curtis-Shapley debate.

a type of pulsating variable star with a luminosity that can be determined from the period of its variation: Cepheids with long pulsation periods are bigger and thus more luminous than short period Cepheids.

A type of variable star used to determine distance. Shapley used a relation between the period of variation of this type of star and its absolute magnitude to calibrate distances to globular clusters during the `Great Debate.' Curtis disputed these distances. Cepheids are used today as reliable distance estimators.

Variable star with a period of 60 days whose period of variation is related to its luminosity. Collectively, all such stars with similar spectra and period/luminosity realtionships.