Standard candles are astronomical objects that have a known intrinsic brightness (luminosity). They are used as reference points to measure distances in the universe. By comparing the known luminosity of a standard candle to its observed brightness as seen from Earth, astronomers can determine how far away the object is. One of the most commonly used types of standard candles is certain types of variable stars, such as Cepheid variables, whose pulsation periods are directly related to their luminosity.
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