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What are cepheid variable stars used for?  | HIX Tutor

There is relation between the pulsations and stars luminosity. 
If the luminosity is known we can calculate the distance by this relation..

Cepheid variables are used in astronomy as standard candles to measure distances.

<a href="http://socratic.org/astronomy/stars-black-holes-and-galaxies/cepheid-variables">Cepheid variables</a> are used in astronomy as standard candles to measure distances.

Levi Anderson

Cepheid variable stars are used as standard candles to measure distances in astronomy. Their pulsation period is directly related to their intrinsic brightness, allowing astronomers to determine their distance by observing their apparent brightness.