multiplestars

Multiplestars refers to stellar systems in which two or more stars are gravitationally bound and orbit a common center of mass. In astronomy, the standard terms are multiple-star system or multiples; multiplestars is a descriptive label for the same concept. These systems range from binaries (two stars) to higher-order configurations such as triples, quadruples, and beyond, and they are common in the galaxy.

Most stars form in multiple systems, and the observed multiplicity depends on stellar mass. For solar-type stars, roughly 40–50% have one or more stellar companions, while the fraction is higher for more massive stars. Many multiples are hierarchical: a close inner binary is orbited by one or more distant companions, creating stable, nested orbital configurations.

Detection and classification rely on several methods. Visual binaries are resolved as two separate stars. Spectroscopic binaries reveal orbital motion through periodic Doppler shifts in spectral lines. Eclipsing binaries are observed when orbital planes align so that stars periodically eclipse each other. Astrometric binaries show a wobble in the star’s position due to an unseen companion. Modern surveys, including Gaia, continue to refine the census and orbital parameters of multiple-star systems.

Dynamics and evolution are shaped by hierarchical structure and gravitational interactions. The Kozai-Lidov mechanism can couple inner and outer orbits, altering eccentricity and inclination over time. These dynamics influence planet formation and stability, making planets in binaries and higher-order systems an active area of study.

Notable examples include the Alpha Centauri system, a triple with two sun-like stars closely bound and Proxima Centauri as a distant companion, and various circumbinary planets such as Kepler-16b.