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ξ Tauri
	; A light curve for Xi Tauri plotted from TESS data
Observation data; Epoch J2000.0 Equinox J2000.0
Constellation	Taurus
Right ascension	03h 27m 10.151s
Declination	+09° 43′ 57.63″
Apparent magnitude (V)	3.73 - 3.81
Characteristics
Spectral type	B9Vn + B9V + B5V + F5V
Variable type	Algol
Astrometry
Proper motion (μ)	RA: 50.58±1.48 mas/yr ; Dec.: −39.54±1.40 mas/yr
Parallax (π)	15.60 ± 1.04 mas
Distance	210 ± 10 ly ; (64 ± 4 pc)
Orbit
Primary	ξ Tau Aa
Companion	ξ Tau Ab
Period (P)	7.146651±0.000010 d
Eccentricity (e)	0.0±0.05
Inclination (i)	86.2±0.5°
Longitude of the node (Ω)	350.5±4.0°
Periastron epoch (T)	JD 2448299.075±0.010
Argument of periastron (ω); (secondary)	90±10°
Semi-amplitude (K1); (primary)	89.1±10.0 km/s
Orbit
Primary	ξ Tau Aa-Ab
Companion	ξ Tau B
Period (P)	145.12±0.055 d
Semi-major axis (a)	16.09±0.18 mas
Eccentricity (e)	0.213±0.007
Inclination (i)	87.07±0.19°
Longitude of the node (Ω)	328.63±0.38°
Periastron epoch (T)	JD 2453712.90±0.34
Argument of periastron (ω); (secondary)	163.07±0.13°
Semi-amplitude (K1); (primary)	38.02±5.0 km/s
Details
ξ Tau Aa
Mass	2.29±0.91 M☉
Radius	2.0±0.2 R☉
Surface gravity (log g)	4.2 cgs
Temperature	9,400±500 K
Rotational velocity (v sin i)	33±2 km/s
ξ Tau Ab
Mass	2.20±0.78 M☉
Radius	1.5±0.2 R☉
Surface gravity (log g)	4.2 cgs
Temperature	9,200±500 K
Rotational velocity (v sin i)	34±2 km/s
ξ Tau B
Mass	3.08±1.24 M☉
Surface gravity (log g)	4.3±0.1 cgs
Temperature	15,100±200 K
Rotational velocity (v sin i)	246±10 km/s
Other designations
	2 Tau, HR 1038, HD 21364, BD+09° 439, HIP 16083, SAO 111195
Database references
SIMBAD	data

Xi Tauri (ξ Tau, ξ Tauri) is a hierarchical quadruple system^[5] in the constellation Taurus.

Xi Tauri is a spectroscopic and eclipsing quadruple star. It consists of three blue-white B-type main sequence stars and an F-type main sequence star. Two of the stars form an eclipsing binary system and revolve around each other once every 7.15 days. These in turn orbit the third star once every 145 days. The fourth star is a F star that orbits the other three stars in a roughly fifty-year period and has been resolved optically.^[7] The brightest and most massive of the four stars is the "third" star, although the eclipsing pair have a greater combined mass and hence are generally considered to be the primary.^[4]

The typical combined apparent magnitude of the system is +3.73, but because the stars eclipse one another during their orbits, it is classified as a variable star, and its brightness varies from magnitude +3.73 to +3.81. Xi Tauri is approximately 210 light years from Earth.^[2]

Nomenclature for the four stars varies. Some sources refer to the faint resolved companion as component C, while others refer to it as B. Similarly, the inner three stars are respectively Aa, Ab, and B, or Aa, Ab, and Ac.^[4]^[5]