Binary star

In Astronomy, a binary star is composed of two star S orbiting around their common Center of gravity.

The binary term star was apparently invented by William Herschel in 1802 to indicate “a true double star - the union of two stars which are formed together in a system by the laws of the gravitation”. Currently, of binary stars are classified in various types according to their observable properties: Binary visual, Binary astrometrical, Binary spectroscopic and Binary with eclipses. The stars can belong to several of these categories, for example several binary spectroscopic are also the binary ones with eclipses. Another classification in three categories is based on the distance from stars: detached binary , semi-detached binary and binary with contact. In this case, it often happens that the binary stars are variable stars.

For a long time the Astronome S considered that approximately half of stars were binary systems (or triple). Today, research on binary stars indicates that the situation is not so simple. The fraction of binary stars according to time can vary indeed, since certain phenomena as the Supernova E can detach a star of his/her companion. Moreover, it is not clearly either if the fraction of binary original, during the formation of stars, is universal or not, and if it is the same one for stars of any initial mass.

Binary examples of stars

Simple: Binary star

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