eclipsing binary

eclipsing binary light curve

Simulated light curve from an eclipsing binary. Image credit: ESA.

An eclipsing binary is a binary star system in which the components periodically pass in front of one another as seen from Earth. When this happens the total light received from the system is reduced. The primary minimum occurs when the component with the higher surface luminosity is eclipsed by its fainter companion.


Three main types of eclipsing binary are distinguished on the basis of their light curves: Algol stars, Beta Lyrae stars, and W Ursae Majoris stars. Eclipses may also occur in some kinds of cataclysmic binary, including dwarf novae, novae, and symbiotic stars. Exactly how the light varies depends on the nature of the component stars and their separation.