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How do astronomers use Cepheid variables to measure distances?

Richard Lynch, Essex Junction, Vermont
RELATED TOPICS: VARIABLE STARS
VISTA views the Trifid Nebula and reveals hidden variable stars.
The simple answer is that the intrinsic brightness of these variable stars is strongly tied to their period. This is the famous period-luminosity relationship discovered by Henrietta Leavitt more than a century ago.

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