eclipsingbinaries

Eclipsing binaries are binary star systems in which the orbital plane is oriented nearly edge-on to the observer, so the stars alternately occult each other as they orbit. The periodic dimming is observable as changes in brightness.

During an eclipse, the primary minimum occurs when the brighter star is obscured, and the secondary minimum occurs when the dimmer star is eclipsed. The depth and shape of the eclipses, together with the orbital period, produce a light curve that encodes information about the relative sizes and surface brightnesses of the stars.

Combined with spectroscopic measurements of radial velocities, eclipsing binaries enable direct determination of absolute stellar masses and radii, testable against theoretical models. They are classified by Roche-lobe filling: detached (neither star fills its Roche lobe), semi-detached (one star fills its Roche lobe), and contact or overcontact (both fill or share an envelope).

These systems are important benchmarks for stellar evolution and for calibrating stellar parameters across a range of masses and metallicities. Eclipsing binaries also provide geometric distance measurements, notably via the eclipsing binary method applied to nearby galaxies like the Large Magellanic Cloud.

Detection and study rely on photometric monitoring and spectroscopic campaigns. Space missions such as Kepler and TESS, along with ground-based surveys, have discovered and characterized large numbers of eclipsing binaries. The well-known eclipsing system Algol is a classic example.