Mizar & Alcor (79 Ursae Majoris) -- Multiple Star System
Horse and Rider
Mizar and Alcor are arguably the most famous of all the double/multiple stars in the night sky.
Mizar and Alcor can be separated without optical aid. Long before the telescope, the ability to
separate the two stars with one’s eyes was a test for good eye-sight. There are many legends
concerning these two stars. One of my favorites is that, if you could visually separate the double,
then you would become an archer in the Persian army. If you couldn't you were subscripted to the
rank-and-file army for hand-to-hand combat. Today, Mizar and Alcor are often referred to as the
Horse and Rider. I have no problem seeing the two together in the handle of the Big Dipper, as
do most people with 20-20 vision.
Mizar was the first telescopic double of its kind to be discovered (Riccioli in 1662). It was the
first double to be photographed (Bond in 1857) and the first spectroscopic binary ever detected
(Pickering in 1889). It was later determined that all three of the telescopic stars (Mizar A,
Mizar B and Alcor) were spectroscopic binaries (double stars that are so close to each other
that they can only be determined to be doubles by their spectrographic signatures).