| Right Ascension | 13 : 23 : 55.5 (h:m:s) |
|---|---|
| Declination | +54 : 55 : 31 (deg:m:s) |
| Distance | 76 (ly) |
| Visual brightness | 2.27 (mag) |
| Spectral type | A1V p SrSi |
Discovered as double star by Benedetto Castelli on February 4, 1617.
Independently found by Giovanni Battista Riccioli around 1650.
The multiple star system zeta UMa (called Mizar - from the arabian word for girdle) belongs to the most famous multiple stars in the sky. It's brightness is about 2.4 mag; therefore under very good conditions it is possible for the naked eye to see the 4th mag. companion, called 'Alcor' or 80 UMa (otherwise a small binocular will help). In small telescops another 4th mag star becomes visible. Each of these stars is as well a spectroscopic binary.
The Mizar system is a member of the nearby Ursa Major Moving Cluster (Collinder 285)