Multiple Star Systems

A multiple star system is a group of three or more stars that are gravitationally bound and orbit around a common center of mass (the barycenter). The most common type of multiple star system is a binary star system, but there are many systems with three or more stars.

Multiple star systems are possible due to the balance of gravitational forces between the stars. While their orbits can be stable over long periods, they are often complex rather than perfectly precise. Small perturbations can influence their trajectories, especially in systems with three or more stars, potentially leading to significant changes or even the ejection of one of the stars in certain cases.

A trinary star system, or triple star system, consists of three stars gravitationally bound to each other. These systems often consist of two stars orbiting closely as a binary, with the third star orbiting the binary at a greater distance.

The Alpha Centauri system is the closest stellar system to Earth. It consists of three stars: Alpha Centauri A, Alpha Centauri B (which form a close binary pair), and Proxima Centauri, which orbits the pair at a much greater distance. Proxima is the closest individual star to our solar system.

The HD 131399 system is a trinary star system located about 320 light-years away in the constellation Centaurus. It features a unique configuration with one of its stars, HD 131399A, being orbited by two other stars, HD 131399B and HD 131399C, in a wide orbit. This system gained attention due to the discovery of a giant planet, HD 131399Ab, which orbits one of the stars in this complex arrangement.

A quaternary star system consists of four stars that are gravitationally bound and orbit around a common center of mass. These systems are typically arranged hierarchically, with two pairs of stars orbiting each other in a stable configuration.

The PH1 system, also known as Kepler-64, is a quaternary star system that contains a circumbinary planet (a planet that orbits two stars). The two central stars are orbited by another pair of stars at a farther distance. This system is notable for being one of the few where a planet has been found in a quaternary system.

The KOI-2626 system is another quaternary system where a planet has been detected. It is a complex system with four stars interacting in a way that results in an unusual orbital configuration, and it demonstrates the possibility of planetary formation in systems with more than two stars.

A quinary star system consists of five stars bound together. These systems are very rare and tend to be arranged hierarchically to maintain stability.

The 1SWASP system is a quintuple star system that gained attention due to its unusual configuration, where five stars are organized in a stable arrangement of close binaries and a more distant companion. Such systems are quite rare, and this one provided insights into the dynamics of quinary star systems.

Other quinary systems are extremely rare and often have unique configurations that are difficult to study due to their complex gravitational interactions. Research into these systems helps expand our understanding of how multiple star systems form and evolve over time.

Yes, systems with more than five stars do exist, but they are exceedingly rare. These systems, known as senary (6) or even higher-order star systems, involve intricate hierarchies of binaries or trinaries orbiting a common center of mass. A well-known example is Castor, a senary star system in which six stars are grouped into three binary pairs. Systems with more than five stars are fascinating because their gravitational dynamics are much more complex, and studying them provides unique insights into the behavior of stars in extreme environments.