What is a Cepheid variable?
Quick Answer
A Cepheid variable is a star whose brightness changes in a regular pattern. Its pulsation period is linked to its true luminosity, making it useful for measuring distance.
The Full Story
Cepheid variables are pulsating stars that expand and contract in a stable cycle. Astronomers discovered that the longer a Cepheid’s period, the brighter it truly is, a relationship first established by Henrietta Swan Leavitt in the early 1900s. This period-luminosity relation makes Cepheids vital standard candles for measuring distances to nearby galaxies. Edwin Hubble used Cepheids to show that the Andromeda Nebula was actually a separate galaxy. Cepheids remain a cornerstone of the cosmic distance ladder.
Key Facts
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"A star that tells you how far away it is by how it flickers."
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