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What are Cepheid variables?

"Cepheid variable" is a name for a certain type of star. Both parts of this name have a special meaning. The "Cepheid" part comes from the name Cepheus, an ancient Greek king, and one of the constellations in the northern sky. The first Cepheid variable was discovered in the constellation Cepheus!

The "variable" part refers to the changing brightness of the star. If you watched a Cepheid variable star for many hours, you would notice that the star gets brighter for a while, and then fainter, and then brighter again... This happens because the surface of the star is pulsating. The star itself grows larger, then shrinks. Imagine your lungs as you are breathing. First they fill with air and expand. Then, as you exhale, they contract. As Cepheid variable stars expand, they get brighter. When they contract, they get fainter.


Submitted by Henrik Berg (Norway)
(February 10, 1998)



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