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Beta Persei / Algol

Beta Persei, better known as the star Algol, is an eclipsing binary star system with a period of 2.87 days. Every 2.87 days the brighter of the two stars is eclipsed by the dimmer star. This causes the star to vary in brightness from mag. 2.1 to mag. 3.4. However, only some of the eclipses are visible during the night from any one location. Algol is located 100 light-years from Earth. Its primary components are a blue giant star (spectral type B8V) and a yellow dwarf star (spectral type G). Long-term observations of the stars' movements have shown that there are actually more than two stars in this system, but little is known about the other components.

James M. Thomas, last updated October 11, 1999.

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