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Mizar

This article is about the star. For other uses, see Mizar (disambiguation).
Mizar
Location of Mizar (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Ursa Major
Mizar
Right ascension 13h 23m 55.54048s[1]
Declination +54° 55′ 31.2671″[1]
Apparent magnitude (V) 2.04[2]
ζ1 UMa
Right ascension 13h 23m 55.543s[3]
Declination +54° 55′ 31.30″[3]
Apparent magnitude (V) 2.23[3]
ζ2 UMa
Right ascension 13h 23m 56.330s[3]
Declination +54° 55′ 18.56″[3]
Apparent magnitude (V) 3.88[3]
Characteristics
ζ1 UMa
Spectral type A2Vp/A2Vp[4]
U−B color index −0.01[5]
B−V color index +0.02[5]
ζ2 UMa
Spectral type kA1h(eA)mA7IV-V[6]
U−B color index +0.09[5]
B−V color index +0.13[5]
Astrometry
Radial velocity (Rv)−6.31[7] km/s
Proper motion (μ) RA: 119.01[1] mas/yr
Dec.: −25.97[1] mas/yr
Parallax (π)39.36 ± 0.30 mas[8]
Distance82.9 ± 0.6 ly
(25.4 ± 0.2 pc)
Absolute magnitude (MV)+0.32/+1.96[9]
Orbit
PrimaryMizar Aa
CompanionMizar Ab
Period (P)20.5386 days[10]
Semi-major axis (a)9.83±0.03[11] mas
Eccentricity (e)0.5415±0.0016[10]
Inclination (i)60.5±0.3[10]°
Longitude of the node (Ω)106.0±0.4[11]°
Periastron epoch (T)RJD 54536.9904[10]
Argument of periastron (ω)
(secondary)		105.27±0.23[10]°
Semi-amplitude (K1)
(primary)		66.478±0.153[10] km/s
Semi-amplitude (K2)
(secondary)		66.019±0.177[10] km/s
Orbit
PrimaryMizar Ba
CompanionMizar Bb
Period (P)175.55 d[12]
Semi-major axis (a)29.849 mas
Eccentricity (e)0.46[12]
Details
Mizar Aa
Mass2.2224±0.0221[10] M☉
Radius2.4 ± 0.1[11] R☉
Luminosity33.3 ± 2.1[11] L☉
Temperature9,000 ± 200[11] K
Age370[13] Myr
Mizar Ab
Mass2.2381±0.0219[10] M☉
Radius2.4 ± 0.1[11] R☉
Luminosity33.3 ± 2.1[11] L☉
Temperature9,000 ± 200[11] K
ζ2 UMa
Surface gravity (log g)4.40[14] cgs
Temperature8,425[14] K
Rotational velocity (v sin i)61[14] km/s
Other designations
ζ Ursae Majoris, ζ UMa, Zeta UMa, 79 Ursae Majoris, BD+55 1598, CCDM J13240+5456, HIP 65378, WDS J13239+5456
ζ1 UMa: GC 18133, HD 116656, HR 5054, PPM 34007, SAO 28737
ζ2 UMa: GC 18134, HD 116657, HR 5055, SAO 28738
Database references
SIMBADMizar
ζ1 UMa
ζ2 UMa

Mizar /ˈmaɪzɑːr/[15] is a second-magnitude star in the handle of the Big Dipper asterism in the constellation of Ursa Major. It has the Bayer designation ζ Ursae Majoris (Latinised as Zeta Ursae Majoris). It forms a well-known naked eye double star with the fainter star Alcor, and is itself a quadruple star system. The Mizar and Alcor system lies about 83 light-years away from the Sun, as measured by the Hipparcos astrometry satellite, and is part of the Ursa Major Moving Group.

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  15. ^ Kunitzsch, Paul; Smart, Tim (2006). A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations (2nd rev. ed.). Cambridge, Massachusetts: Sky Pub. ISBN 978-1-931559-44-7.

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