Star system
Astar systemorstellar systemis a small number ofstarswhich orbit each other, bound bygravitational attraction.[1]
A large number of stars bound by gravitation is generally called astar clusterbut, broadly speaking, they are also star systems. Star systems are not to be confused withplanetary systems,which include planets and similar bodies.
A stellar system of two stars is known as abinary star,binary star systemorphysicaldouble star.If there are notidaleffects, no disturbance from other forces, and no transfer ofmassfrom one star to the other, such a system isstable.Both stars willorbitaround thecenter of massof the system indefinitely. Examples of binary systems areSirius,ProcyonandCygnus X-1,the last of which probably consists of a star and ablack hole.
Multiple star systems
[change|change source]It is possible to have star systems with more than two members. Their stars aregravitationallybound to each other, and may or may not be close to each other.[2][3][4][5]
A recently discovered quintuple star system (five stars) is known as 1SWASP J093010.78+533859.5.[6]The system has two sets of binary stars, one of them with a small third star. The two sets are a long way apart, further than theorbitofPlutois to the Sun. The binary stars are close to each other and one binary has touching stars, with their outerionisedgases mi xing. That situation is called a contact binary. From the data collected, the authors are fairly sure that both binaries (and probably all five stars) are gravitationally bound in a single system. The angles of inclination (the angle between the two orbital planes) of the two binaries (88.2(3) and 86(4) degrees). This suggests they originally formed by break-up (~9-10billionyears ago ago) from a single protostellar disk. Afterwards, they stayed in the sameorbital plane.[6]
Most multiple star systems aretriple stars.Systems with four or more components are less likely to occur.[4]
Multiple star systems are smaller thanopen star clusters,which have more complex dynamics and typically have from 100 to 1,000 stars.[7][7]Most multiple star systems known are triple.[8]For example, in the 1999 revision of Tokovinin's catalog of physical multiple stars, 551 out of the 728 systems described are triple.
Multiple-star systems can be divided into two main types: systems which are stable, or systems withchaoticbehavior.[9]Chaotic ones are usually of young stars in systems not yet disrupted by the chaos.
References
[change|change source]- ↑"Star system" inModern Dictionary of Astronomy and Space Technology.A.S. Bhatia, ed. New Delhi: Deep & Deep Publications, 2005.ISBN81-7629-741-0
- ↑Percy, John P. 2007.Understanding variable stars.Cambridge University Press, p16.ISBN0-521-23253-8
- ↑Hipparcos: double and multiple stars,web page, accessed October 31, 2007.
- ↑4.04.1MSC – a catalogue of physical multiple starsA.A. Tokovinin 1997.Astronomy and Astrophysics Supplement Series124pp. 75–84.
- ↑Binary and multiple starsArchived2008-04-23 at theWayback Machine,web page, accessed May 26, 2007.
- ↑6.06.1Lohr M.E.et al2015. The doubly eclipsing quintuple low-mass star system 1SWASP J093010.78+533859.5. arXiv.org[1]
- ↑7.07.1p. 24,Galactic Dynamics,James Binney and Scott Tremaine, Princeton University Press, 1987,ISBN0-691-08445-9.
- ↑Statistics of multiple stars: some clues to formation mechanismsArchived2007-09-27 at theWayback Machine,A. Tokovinin, in the proceedings of IAU Symposium 200, The Formation of Binary Stars, Potsdam, Germany, 10 April–15, 2000. Bibcode2001IAUS..200...84T.
- ↑P.J.T. Leonard 2001. Multiple stellar systems: types and stability. InEncyclopedia of Astronomy and Astrophysics,P. Murdin (ed) online edition atInstitute of PhysicsArchived2012-07-09 atArchive.today