Binary Star (Encyclopedia of Science)
A binary star, often called a double star, is a star system in which two stars linked by their mutual gravity orbit around a central point of mass. Binary stars are quite common. A recent survey of 123 nearby Sun-like stars showed that 57 percent had one or more companions.
English astronomer William Herschel (1738822) made the first discovery of a true binary system in the 1700s. He observed the motion of a pair of stars and concluded that they were in orbit around each other. Herschel's discovery provided the first evidence that gravity exists out-side our solar system.
Herschel discovered more than 800 double stars. He called these star systems binary stars. His son, John Herschel (1792871), continued the search for binaries and catalogued over 10,000 systems of two or more stars.
(The entire section is 567 words.)
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