A star system or stellar system is a small number of stars that orbit each other,^[1] bound by gravitational attraction. A large number of stars bound by gravitation, is called a star cluster or galaxy, although they are star systems of a broad definition. This article is about the astronomical object. ... Gravity redirects here. ... This article or section does not cite its references or sources. ... NGC 4414, a typical spiral galaxy in the constellation Coma Berenices, is about 17,000 parsecs in diameter and approximately 20 million parsecs distant. ...

Binary star systems

Main article: Binary star

The binary representation of Alpha Centauri; it is more commonly classified as a Triple star system.

A stellar system of two stars is known as a binary star, binary star system or physical double star. If there are no tidal effects, no perturbation from other forces, and no transfer of mass from one star to the other, such a system is stable, and both stars will trace out an elliptical orbit around the center of mass of the system indefinitely. See Two-body problem. This article is about the astronomical phenomenon. ... Image File history File links Generated by author/contributor. ... Image File history File links Generated by author/contributor. ... Alpha Centauri (α Cen / α Centauri) is the brightest star system in the southern constellation of Centaurus. ... A triple star system consists of three gravitationally bound stars. ... This article is about the astronomical phenomenon. ... When two stars are so nearly in the same direction as seen from Earth that they appear to be a single star to the naked eye but may be separated by the use of telescopes, they are referred to as a double star. ... Comet Shoemaker-Levy 9 after breaking up under the influence of Jupiters tidal forces. ... Unsolved problems in physics: What causes anything to have mass? The U.S. National Prototype Kilogram, which currently serves as the primary standard for measuring mass in the U.S. Mass is the property of a physical object that quantifies the amount of matter and energy it is equivalent to. ... The ellipse and some of its mathematical properties. ... In physics, an orbit is the path that an object makes, around another object, whilst under the influence of a source of centripetal force, such as gravity. ... In physics, the center of mass of a system of particles is a specific point at which, for many purposes, the systems mass behaves as if it were concentrated. ... In classical mechanics, the two-body problem is to determine the motion of two point particles that interact only with each other. ...

Examples of binary systems are Sirius and Cygnus X-1, the latter probably consisting of a star and a black hole. For information on Sirius satellite radio, see Sirius Satellite Radio. ... Location of the X-ray source Cygnus X-1, which is widely accepted to be a 10 solar mass black hole orbiting a blue giant star. ... A black hole is an object predicted by general relativity,[1] with a gravitational field so powerful that even electromagnetic radiation (such as light) cannot escape its pull. ...

Multiple star systems

Multiple star systems or physical multiple stars are systems of several stars. These systems have relatively simple orbital dynamics compared with star clusters and galaxies with their large numbers of stars. Triple star systems are the most common multiple star systems. A multiple star consists of three or more stars which appear from the Earth to be close to one another. ... In physics, dynamics is the branch of classical mechanics that is concerned with the effects of forces on the motion of objects. ... This article or section does not cite its references or sources. ... NGC 4414, a typical spiral galaxy in the constellation Coma Berenices, is about 17,000 parsecs in diameter and approximately 20 million parsecs distant. ... A triple star system consists of three gravitationally bound stars. ...

Nomenclature

Multiple star systems are called triple, trinary or ternary if they contain three stars; quadruple or quaternary if they contain four stars; quintuple with five stars; sextuple with six stars; septuple with seven stars; and so on.

Dynamical theory

Theoretically, modelling a multiple star system is more difficult than modelling a binary star, as the dynamical system involved, the n-body problem, may exhibit chaotic behavior. Many configurations of small groups of stars are found to be unstable, as eventually one star will approach another closely and be accelerated so much that it will escape from the system.^[2] This instability can be avoided if the system is what Evans^[3] has called hierarchical. In a hierarchical system, the stars in the system can be divided into two smaller groups, each of which traverses a larger orbit around the system's center of mass. Each of these smaller groups must also be hierarchical, which means that they must be divided into smaller subgroups which themselves are hierarchical, and so on. A dynamical system is a concept in mathematics where a fixed rule describes the time dependence of a point in a geometrical space. ... The n-body problem is the problem of finding, given the initial positions, masses, and velocities of n bodies, their subsequent motions as determined by classical mechanics, i. ... A plot of the trajectory Lorenz system for values r = 28, σ = 10, b = 8/3 In mathematics and physics, chaos theory describes the behavior of certain nonlinear dynamical systems that under certain conditions exhibit a phenomenon known as chaos. ... In physics, the center of mass of a system of particles is a specific point at which, for many purposes, the systems mass behaves as if it were concentrated. ...

Triple star systems

It has been suggested that triple star system be merged into this article or section. (Discuss)

Triple systems are by far the most common type of multiple system. For example, in the 1999 revision of Tokovinin's catalog^[4] of physical multiple stars, 551 out of the 728 systems described are triple. In accordance with the hierarchical principle, triple star systems generally contain a close binary pair which has a more distant companion. Image File history File links Please see the file description page for further information. ... A triple star system consists of three gravitationally bound stars. ...

Higher multiplicities

Many systems with more than three stars are known to exist. Castor (Alpha Geminorum) contains at least six stars. This consists of a binary pair in a distant orbit of two close binary pairs. Castor (α Gem / α Geminorum / Alpha Geminorum) is the second brightest star in the constellation Gemini and one of the brightest stars in the nighttime sky. ...

Examples

Some multiple star systems are:

• Alpha Centauri (three stars) [debated - see Proxima Centauri]
• 4 Centauri (four stars)
• Mizar (four stars)
• Nu Scorpii (five stars)
• Castor (six stars)

Alpha Centauri (α Cen / α Centauri) is the brightest star system in the southern constellation of Centaurus. ... It has been suggested that this article or section be merged into Alpha Ccentauri. ... 4 Centauri is a star in the constellation Centaurus. ... Mizar (ζ UMa) is a star in the constellation Ursa Major and is the second star from the end of the Big Dippers handle. ... Nu Scorpii (ν Sco / ν Scorpii) is a star system in the constellation Scorpius. ... Castor (α Gem / α Geminorum / Alpha Geminorum) is the second brightest star in the constellation Gemini and one of the brightest stars in the nighttime sky. ...

See also

• Solar System
• Binary star
• Triple star system
• Quadruple star system
• Planetary system
• Extrasolar planet

Major features of the Solar System (not to scale, from left to right): Pluto, Neptune, Uranus, Saturn, Jupiter, the asteroid belt, the Sun, Mercury, Venus, Earth & Moon, and Mars. ... This article is about the astronomical phenomenon. ... A triple star system consists of three gravitationally bound stars. ... A quadruple star system or quaternary star system is a star system composed of four stars. ... An artists concept of a protoplanetary disc. ... An extrasolar planet, or exoplanet, is a planet beyond the Solar System. ...

References

1. ^ "Star system" in Modern Dictionary of Astronomy and Space Technology. A.S. Bhatia, ed. New Delhi: Deep & Deep Publications, 2005. ISBN 81-7629-741-0
2. ^ Multiple Stellar Systems: Types and Stability, Peter J. T. Leonard, in Encyclopedia of Astronomy and Astrophysics, P. Murdin, ed., online edition at the Institute of Physics, orig. ed. published by Nature Publishing Group, 2001.
3. ^ Stars of Higher Multiplicity, David S. Evans, Quarterly Journal of the Royal Astronomical Society 9 (1968), 388–400.
4. ^ MSC—a catalogue of physical multiple stars, A. A. Tokovinin, Astronomy and Astrophysics Supplement Series 124 (1997), 75–84; online versions at VizieR and the Multiple Star Catalog.