Cepheid Variables are very luminous stars, 500 to 300,000 times greater than the Sun, with short periods of change that range from 1 to 100 days. They are pulsating variables that expand and shrink dramatically within a short period of time, following a specific pattern. Astronomers can make distance measurements to a Cepheid by measuring the variability of its luminosity, which makes them very valuable to the science.
Other pulsating variables include RR Lyrae, short period, older stars that are not as large as Cepheids; and RV Tauri stars, supergiants with greater light variations. Long-period pulsating variables include the Mira, which are cool red supergiants with large pulsations; and Semiregular, which are red giants or supergiants with longer periods that can range from 30 to 1000 days. One of the best-known Semiregular Variables is Betelgeuse. Irregular pulsating variables have also been identified. These are usually red supergiants, but very little study has been done on them.
Sources and More Reading: