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A '''Cepheid''', more commonly referred to as a '''Cepheid variable''', is a type of pulsating [[variable star]] whose periods of variability is directly related to their absolute luminosity. This precise relationship between the star's pulsation period and luminosity makes the stars invaluable indicators of astronomical distances. Today Cepheid variables are one of the methods astronomers use to determine the distances to celestial objects in the universe, known collectively as the [[cosmic distance ladder]]. They are seen as ''standard candles'', that is astronomical objects that have a known luminosity. The best known and closest Cepheid variable to us is the current North Star [[Polaris]].