Mizar
Quadruple star system in Ursa Major / From Wikipedia, the free encyclopedia
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This article is about the star. For other uses, see Mizar (disambiguation).
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.
Quick Facts Observation data Epoch J2000 Equinox J2000, Apparent magnitude (V) ...
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] |
Distance | 82.9 ± 0.6 ly (25.4 ± 0.2 pc) |
Absolute magnitude (MV) | +0.32/+1.96[9] |
Orbit | |
Primary | Mizar Aa |
Companion | Mizar 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 | |
Primary | Mizar Ba |
Companion | Mizar Bb |
Period (P) | 175.55 d[12] |
Semi-major axis (a) | 29.849 mas |
Eccentricity (e) | 0.46[12] |
Details | |
Mizar Aa | |
Mass | 2.2224±0.0221[10] M☉ |
Radius | 2.4 ± 0.1[11] R☉ |
Luminosity | 33.3 ± 2.1[11] L☉ |
Temperature | 9,000 ± 200[11] K |
Age | 370[13] Myr |
Mizar Ab | |
Mass | 2.2381±0.0219[10] M☉ |
Radius | 2.4 ± 0.1[11] R☉ |
Luminosity | 33.3 ± 2.1[11] L☉ |
Temperature | 9,000 ± 200[11] K |
ζ2 UMa | |
Surface gravity (log g) | 4.40[14] cgs |
Temperature | 8,425[14] K |
Rotational velocity (v sin i) | 61[14] km/s |
Other designations | |
ζ1 UMa: GC 18133, HD 116656, HR 5054, PPM 34007, SAO 28737 | |
ζ2 UMa: GC 18134, HD 116657, HR 5055, SAO 28738 | |
Database references | |
SIMBAD | Mizar |
ζ1 UMa | |
ζ2 UMa |
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