eclipsing binary

Schematic of orbits and light curve of eclipsing binary

eclipsing binary

A binary star whose orbital plane is orientated such that each component is totally or partly eclipsed by the other during each orbital period. The effect observed is a periodic decrease in the light from the system (see illustration). The deeper minimum corresponds to the eclipse of the brighter star. The light curve gives the period of revolution, and from the depths and shapes of the minima it is possible to estimate the inclination of the orbital plane. The duration of the eclipses compared to the time between eclipses indicates the radii of the stars in terms of the distance between them. If the system is also a double-lined spectroscopic binary the individual masses and radii of the stars can be calculated.

Eclipsing binaries tend to be composed of large stars with small orbits and therefore the majority are close binaries (see binary star). In these systems mass transfer affects the stars' evolution, leading to three main classes of eclipsing binaries. W Ursae Majoris stars are in contact. In W Serpentis stars one component is transferring mass rapidly to the other. In these two classes the stars are distorted into ellipsoids, an effect that shows in the light curve. Algol variables represent a later stage; mass transfer is almost complete and the stars are nearly spherical.

Collins Dictionary of Astronomy © Market House Books Ltd, 2006

eclipsing binary

[i′klips·iŋ′bī‚nər·ē]

(astronomy)

eclipsing variable star

McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.