Cepheid Variables

All stars, late in their lifetime, change from being average stars for their mass ( main sequence stars ) to becoming swollen red giants . Most stars change from the swollen red giant phase to pulsating variable stars before they finally die, all reactions ceasing. These are Cepheid Variables, which expand and contract, glowing brightly and fading every so often.

Figure 1

Cepheid Variables are very large, luminous, yellow stars. They change in brightness very regularly with periods of 1 to 70 days between peaks. The stars are called Cepheids after the first star of this type to be discovered - Delta Cephei. This is a reasonably bright star in the constellation of Cepheus (Figure 1). As the light curve of Delta Cephei shows (Figure 2) it has a period of about 5 days.

Figure 2

* Click here to learn how Cepheids help us to calculate distances

* Click here to find out about the magnitude scale