Mizar — Double Star in Ursa Major
Zeta UMa (BS5054)
About Mizar
Description
Mizar is a white star of spectral type A1VpSrSi at magnitude 2.27 in Ursa Major, famous as one of the most celebrated double stars in history. Its naked-eye companion Alcor (magnitude 4.0) sits just 12 arcminutes away. Mizar itself was the first telescopic double star discovered (1617), and each component is a spectroscopic binary — making the system at least a sextuple.
Observing Tips
Mizar is the middle star of the Big Dipper's handle. Look carefully with the naked eye for the fainter companion Alcor just beside it — the Mizar-Alcor pair is one of the oldest known naked-eye double star tests. A small telescope at moderate magnification splits Mizar itself into two components separated by about 14 arcseconds. Best observed March through August.
History
The name Mizar comes from the Arabic 'mi'zar,' meaning 'girdle' or 'waistcloth.' The ability to see Alcor beside Mizar was used as an eyesight test by many cultures, including the Arabs, Romans, and Native Americans. Mizar A was the first spectroscopic binary star discovered, by Edward Pickering in 1889.
Fun Facts
Mizar holds multiple 'firsts' in stellar astronomy: first telescopic double (1617), first photographed star (1857, along with Vega), and its component Mizar A was the first spectroscopic binary discovered (1889). The Mizar-Alcor system may contain six or more stars all gravitationally bound.
Observe
1Physical Properties
2Position & Identifiers
3How easy to split?
| Telescope | Bortle 3 | Bortle 4 | Bortle 5 |
|---|---|---|---|
| 80 mm refractor 80mm refr. | Easy | Easy | Easy |
| 150 mm Newton 150mm Newt. | Easy | Easy | Easy |
| Celestron C8 (203 mm SCT) C8 203mm | Easy | Easy | Easy |
Bortle 3 = rural · 4 = outer suburbs · 5 = suburbs
4Visibility
Set a location in User Settings to see visibility data.
5Multiple Star System Quadruple D: optical
Separation over time
Essentially fixed on human timescales — the same view your grandchildren will see.
Measured from the WDS observational archive. No orbital solution has been derived — most likely the period is too long to fit an orbit to the available measurement arc.
Eyepiece View
A: 2.3 · B: 3.9 · Sep: 14.4″ · PA: 153° · N up, E right
Resolved · Rayleigh: 2.3″ · Dawes: 1.9″ · Eff: 2.3″
Explore
7
Size Comparison
8
Compare Stars
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Spectral Classification
10
Hertzsprung-Russell Diagram
11
Stellar Lifecycle
12
Blackbody Spectrum
13
Stellar Absorption Spectrum
Simulated absorption spectrum based on spectral type. Hover over lines to identify elements.
14
Stellar Fusion
Discover
15Stellar Notes
16
Light Travel Time Machine
17
Relativistic Travel
Nearby in the Sky
Other targets within a few degrees — pan your scope a little and keep exploring.
Visibility scores assume a 150 mm Newton at Bortle 4.
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