Zeta Tauri

ζ Tauri
Location of ζ Tauri (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Taurus
Right ascension 05h 37m 38.68542s[1]
Declination +21° 08′ 33.1588″[1]
Apparent magnitude (V) 3.010[2] (2.88–3.17[3])
Characteristics
Spectral type B2 IIIpe[4]
U−B color index −0.749[2]
B−V color index −0.164[2]
Variable type γ Cas[3]
Astrometry
Radial velocity (Rv)+20[5] km/s
Proper motion (μ) RA: +1.78[1] mas/yr
Dec.: −20.07[1] mas/yr
Parallax (π)7.33 ± 0.82 mas[1]
Distanceapprox. 440 ly
(approx. 140 pc)
Absolute magnitude (MV)−2.67[6]
Orbit[4]
Period (P)132.987 d
Semi-major axis (a)1.17 AU
Eccentricity (e)0.0 (assumed)
Inclination (i)92.8°
Longitude of the node (Ω)−58.0°
Periastron epoch (T)2,447,025.6 HJD
Argument of periastron (ω)
(secondary)		0.0 (assumed)°
Semi-amplitude (K1)
(primary)		7.43 km/s
Details
ζ Tau A
Mass11.2[4] M☉
Radius5.5[4] R☉
Luminosity4,169[7] L☉
Temperature15,500[7] K
Rotational velocity (v sin i)125[8] km/s
Age22.5 ± 2.6[9] Myr
ζ Tau B
Mass0.94[4] M☉
Other designations
Tianguan, 123 Tauri, HR 1910, HD 37202, BD+21°908, FK5 211, HIP 26451, SAO 77336, GC 6985[10]
Database references
SIMBADdata

Zeta Tauri (ζ Tauri, abbreviated Zeta Tau, ζ Tau) is a binary star in the zodiac constellation of Taurus, the Bull. It has an apparent visual magnitude of about 3.0, which is bright enough to be seen with the naked eye. Parallax measurements place it at a distance of roughly 440 light-years from the Sun.

The two components are designated Zeta Tauri A (officially named Tianguan /tiænˈɡwɑːn/) and Zeta Tauri B.

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