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Mizar

Zeta UMa (BS5054)

Observable Double Star Excellent (71/100)

Sep: 14.4", Companion: mag 3.9

HIP 65378; Zeta UMa; 79 UMa DoubleStar UMa Visible Level 2 Small telescope (4") - Requires steady seeing
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Physical Properties

Magnitude 2.27
Spectral Type A1VpSrSi
Star Color White (B-V 0.02)
Distance 69.4 ly

Position & Identifiers

RA 13h 23m 55.5s
Dec +54° 55' 31.0"
Constellation UMa
HR 5054
HIP 65378
Bayer Zeta
Flamsteed 79 UMa
Double Cat 8891

Visibility

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Multiple Star System

Components 4
Component IDs AP
Separation 14.4″
Companion Mag 3.9
Position Angle 153°
Star Colors A: White B: White
Discoverer STF1744

Eyepiece View

80x Dawes: 1.9″ TFOV: 0.6°
Realistic = true angular size
N E 153° A (2.3) B (3.9)

Sep: 14.4″ · PA: 153° · N up, E left

Resolved · Rayleigh: 2.3″ · Dawes: 1.9″ · Eff: 3.1″

Size Comparison

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Stellar Lifecycle

Spectral Classification

Hertzsprung-Russell Diagram

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Blackbody Spectrum

Stellar Absorption Spectrum

Simulated absorption spectrum based on spectral type. Hover over lines to identify elements.

Stellar Notes

Aa = AP 3.0 A2V, 3.0 A2V, sep. 0.0115", 0.056y, a = 0.012". Combined mag., colors AP. Binary with HR 5055. Alcor, | HR 5062, at 709", CPM.
ADS 8891Aa, 20.5386d, K 68.8k/s, V0 -5.6k/s, msin3i 1.60, asini 16.4. i 60d. vsini both components 32k/s. The | first SB to have been discovered, by Pickering in 1889. First resolved by 20-foot interferometer at Mt. Wilson by Pease | in 1925, sep. 0.01".
"Dipper Stars;" Sirius group; UMa moving cluster.
Combined spectrum for Aa also classified A1VpSrSi.
0.046".
MIZAR; Mizat; Mirza.

Survey Image

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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.