Known simply as "Cepheids," Cepheid variables, or standard candles, these are stars that periodically brighten and dim. This behavior allows astronomers to use them as cosmic standards to measure distances of several million light years. Their magnitudes vary from hundredths to 2 units. The most important thing about them is the relationship between your period and your luminosity.
There are two main groups of Cepheids:
- Typical Cepheids whose type star is delta cephei, called population I stars.
- The W Virginis type Cepheids to which the population II stars belong.
