Definition of optical double in US English:

optical double


  • Two stars that are in the same line of sight as seen from the earth, but that may be at far different distances.

    See also double star
    • ‘At first he figured that such pairs consisted of two stars vastly distant from each other but coincidentally lying along a single line of sight - a visual phenomenon we now call optical doubles.’
    • ‘The physical doubles (or binary stars) are much more numerous than the optical doubles.’