Algol and Other Variables

Compared to other eclipsing variables, Beta Persei is unique with its great brightness and relatively short period of variation.

Unlike like other types of variables belonging to the intrinsic group, the change of magnitude in Algol is not caused by changes inside a star. For example, pulsating variables change because they expand and shrink; eruptive variables erupt, increasing their brightness. The variability of Beta Persei is only caused by the fact than one of the components eclipses the other – there is no change in the stars themselves.