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optical binary

American  

noun

plural

optical binaries

  1. Astronomy. a pair of stars that appear close together when observed from Earth, but which are not actually close in physical space.

optical binary Scientific  

  1. See under binary star

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Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.