Mizar
Designations
- Bayer: ζ UMa
- Flamsteed: 79 UMa
- Hipparchos: HIP 65378 A
Data
- Constellation: Ursa Major
- Apparent Magnitude: 2.22
- Right Ascension (J2000): 13h23m55.32s
- Declination (J2000): +54°55'49".0
- Colour Index (B-V): 0.05
- Distance: 81.09±0.93ly
Description
Mizar is arguably the most well-known of the stars of the Big Dipper, as it forms a naked-eye double with the close-by star Alcor (80 UMa). The pair actually form a gravitationally-bound system with Mizar being a quadruple star and Alcor a double star, making the whole a sextuple system. Resolving the pair has been an important test of eyesight since ancient times. In-between the pair and slightly to the south lies the eighth magnitude Stella Ludoviciana, once thought to be a new planet by its discoverer Johann Georg Liebknecht but actually being a star roughly 3.5 times more distant than Mizar and Alcor.
Nomenclature
Mizar
The name is ultimately from the scientific Arab term for β UMa, Mirāqq al-Dubb al-Akbar. It was abbreviated and transliterated variously as Mirac, Mirach, etc.. However, the Arabic term mi'zar was also transliterated as Mirac, Mirach, etc., leading to confusion between the terms regarding star naming. As a result, the medieval name for β UMa erroneously became Mizar, but in late Renaissance times Mizar was misapplied to ζ UMa while β correctly became Merak.