Glossary term: Binary Star


A binary star is a system of two stars that orbit around a common center of gravity, and thus can be said to be bound together by a force of gravity. Their orbits are elliptical or circular and follow Kepler's laws of motion.

More than half, if not the majority, of stars in the Milky Way are binary stars or part of several more complex systems that, due to their enormous distance from Earth, appear to the human eye as a single star.
Binaries can be classified into a number of subclasses according to their optical properties, namely visual binaries, spectroscopic binaries, eclipsing binaries, non-eclipsing binaries that can be detected through photometry, and astrometric binaries.

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