Mizar and Alcor
DOUBLE STAR · the eyesight test
Look at the middle of the Big Dipper's handle: can you see the faint star snuggled against the bright one? For centuries, spotting Alcor beside Mizar was used as a test of good eyesight. The pair hides more: Mizar alone is four stars, two close pairs, and with Alcor's companion the whole system counts six suns.
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