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Mizar and Alcor

Mizar and Alcor is the most famous double star in the sky. Both partners form the middle of the handle of the Big Dipper. At good conditions the double can be seen without problems. However it is not sure if Mizar and Alcor really orbit each other or only are neighbors.
Mizar itself is a quadruple system. All 5 stars are white to blue main sequence stars.

Constellation: Ursa Major
Distance of Mizar: 78.2 light-years
Distance of Alcor: 81.2 light-years
Space between Mizar Aa and Mizar Ab: 0.29 AU
Orbit period of Mizar Aa and Mizar Ab: 20.454 days
Space between Mizar Ba and Mizar Bb: 3.12 AU
Orbit period of Mizar Ba and Mizar Bb: 57 years
Space between Mizar A and Mizar B: 345 AU
Space between Mizar and Alcor: 200 000 AU

Mizar Aa and Ab

Spectral class Aa and Ab: A1
Visual magnitude Aa and Ab: 2.25
Luminosity Aa and Ab: 63 * Sun
Mass Aa: 7.7 * Sun
Diameter Aa: 4.12 * Sun

Mizar Ba and Bb

Spectral class Ba and Bb: A1
Visual magnitude Ba and Bb: 3.95
Luminosity Ba and Bb: 13.2 * Sun

Diameter Ba: 3.89 * Sun


Spectral class: A5
Visual magnitude: 4.01
Luminosity: 13.4 * Sun

Diameter: 1.76 * Sun

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    Mizar and Alcor
Photo: ESO Online Digitized Sky Survey

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