A type of variable star that pulsates radially, varying in both diameter and temperature in a regular cycle. Cepheids follow a period-luminosity relationship, making them crucial standard candles for measuring cosmic distances.
Named after Delta Cephei, the prototype star in the constellation Cepheus where this variability was first discovered in 1784. The class was established as astronomers found more stars with similar pulsating behavior.
Cepheid variables are the cosmic lighthouses that helped us discover the universe is expanding! Henrietta Swan Leavitt's discovery of their period-luminosity relationship in 1908 gave us our first reliable way to measure distances to other galaxies.
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