A class of variable stars that brighten and dim in a regular, predictable pattern, used by astronomers to measure distances to galaxies.
Named after Delta Cephei, the first star of this type discovered in the constellation Cepheus. The '-eids' suffix indicates they are similar to the prototype star in the constellation.
Cepheids are astronomy's cosmic measuring sticks—by watching how their brightness changes in a predictable pattern, astronomers discovered they could calculate exact distances to other galaxies, a breakthrough that revealed the universe is vastly larger than anyone imagined and fundamentally changed our cosmic perspective.
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