binary star

2 ENTRIES FOUND:

binary star

noun

Definition of BINARY STAR

:  a system of two stars that revolve around each other under their mutual gravitation

First Known Use of BINARY STAR

circa 1844

binary star

noun    (Concise Encyclopedia)

Pair of stars in orbit around a common centre of gravity. Their relative sizes and brightnesses and the distance between them vary widely. Perhaps half of all stars in the Milky Way Galaxy are binaries or members of more complex multiple systems. Some binaries form a class of variable stars (see eclipsing variable star). Stars can be identified as binaries in various ways—visually by telescope, through spectroscopic observation, by changes in apparent brightness (when the dimmer star eclipses its companion), or by changes in the proper motion of the visible member (owing to the gravitational pull of the invisible companion).

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