Mizar, designated Zeta Ursae Majoris (ζ UMa), and Alcor, designated 80 Ursae Majoris (80 UMa), are 2 stars that form a naked eye double in Ursa Major.
Appearance
Since the 4 A-type stars are far brighter than the 2 red dwarfs, both stars appear blue.
Mizar is brighter with an apparent magnitude of 2.04, while Alcor has apparent magnitude 3.99. Adding those results in a combined apparent magnitude of 1.87.
Star system
The stars are actually gravitationally bound, and form a star system composed of 6 stars. This is because Mizar is actually 2 pairs of binary stars, and Alcor is a binary star. However, Mizar A and B orbit too close to each other to be able to be differentiated by the naked eye, and the inner pairs need spectroscopy to be differentiated. Both stars are part of the Ursa Major moving group.
The 6 stars are:
Mizar Aa and Ab are A dwarfs with about 2.23 M☉, Mizar Ba and Alcor A are also A dwarfs but are slightly less massive at around 1.85 M☉, and Mizar Bb and Alcor B are both red dwarfs with 0.25 M☉.