Alrediph Delta Cephei the prototype standard candle

Alrediph or Delta Cephei, is the prototype star of the class of  Cepheid variables and located in the constellatioin Cepheid. Its apparent visual magnitude at minimum is 4.34 and at maximum 3.51, changing in a regular cycle of about five days and nine hours. Its variations in brightness is imporatant becayse there’s a relationship between the length of each beat and the star’s brightness. Astronomers can use that relationship to measure the star’s distance. That makes them valuable tools or standard candles for helping to measure the scale of the universe.