Illustration of the eclipsing binary star systems known as Algols. Algol is the prototype of eclipsing binary variable stars, in which two stars in mutual orbit periodically cut out each other's light as seen from Earth. Algol itself comprises a cool orange star and a hot white star. As the orange star eclipses the brighter white star, every 2.87 days, the system's magnitude as seen from Earth drops from 2.2 to 3.5, as shown in the graph at the bottom. The reverse eclipse causes a far smaller drop of only 0.06. It is thought that the white star is also drawing matter from its larger companion, as the system erratically flares up in radio wavelengths due to matter falling onto the star.