Epoch J2000 Equinox J2000
|Right ascension||12h 19m 54.35783s|
|Declination||–00° 40′ 00.5095″|
|Apparent magnitude (V)||3.890|
|Spectral type||A2 V|
|U−B color index||+0.055|
|B−V color index||+0.029|
|Radial velocity (Rv)||+2.3 km/s|
|Proper motion (μ)||RA: –57.58 mas/yr
Dec.: –25.19 mas/yr
|Parallax (π)||12.29 ± 0.45 mas|
|Distance||265 ± 10 ly
(81 ± 3 pc)
|Primary||η Vir Aa|
|Companion||η Vir Ab|
|Period (P)||71.7919 ± 0.0009 days|
|Eccentricity (e)||0.2519 ± 0.0040|
|Inclination (i)||45.5 ± 0.9°|
|Periastron epoch (T)||54403.6116 ± 0.3406|
|Argument of periastron (ω)
|197.21 ± 1.74°|
|26.606 ± 0.198 km/s|
|35.236 ± 0.273 km/s|
|η Vir Aa|
|Mass||2.5039 ± 0.1246 M☉|
|Surface gravity (log g)||3.0 cgs|
|Metallicity [Fe/H]||+0.11 dex|
|Rotational velocity (v sin i)||18 km/s|
|η Vir Ab|
|Mass||1.8907 ± 0.0932 M☉|
Eta Virginis (η Vir, η Virginis) is a multiple star system in the zodiac constellation of Virgo. It has the traditional name Zaniah //. From parallax measurements, the distance to this star was found to be roughly 265 light-years (81 parsecs). It has an apparent visual magnitude of 3.89, which is bright enough for the system to be seen with the naked eye in dark skies.
Although the star looks single, lunar occultations have shown this star to be a very close triple star system consisting of two stars only 0.5 AU apart with a third slightly more distant star. The inner pair is a spectroscopic binary that completes an orbit with a period of 72 days. The inclination of this orbit was determined through interferometer observations to be 45.5°, which allowed the individual masses of the two stars to be estimated. The primary star, η Vir Aa, has a mass of about 2.5 times the Sun's mass, while the secondary, η Vir Ab, has 1.9 solar masses. The faint tertiary star, η Vir B, orbits the inner group in a wider orbit over a period of 13.1 years.
Because Zaniah is near the ecliptic, it can be occulted by the Moon and (very rarely) by planets. On October 12, 272 BC, the ancient Greek astronomer Timocharis observed a conjunction of the star with Venus. The last occultation by a planet took place on September 27, 1843, also by Venus, which will occult it again on November 19, 2445.
The medieval name Zaniah is from the Arabic زاوية zāwiyah "corner", the same source as Zavijava.
In the catalogue of stars in the Calendarium of Al Achsasi Al Mouakket, this star was designated Thanih al Aoua, which was translated into Latin as Secunda Latratoris, meaning the second barker. This star, along with β Vir (Zavijava), γ Vir (Porrima), δ Vir (Auva) and ε Vir (Vindemiatrix), were Al ʽAwwāʼ, the Barker.
In Chinese, 太微左垣 (Tài Wēi Zuǒ Yuán), meaning Left Wall of Supreme Palace Enclosure, refers to an asterism consisting of η Virginis, γ Virginis, δ Virginis, ε Virginis and α Comae Berenices. Consequently, η Virginis itself is known as 太微左垣一 (Tài Wēi Zuǒ Yuán yī, English: the First Star of Left Wall of Supreme Palace Enclosure.), representing 左執法 (Zuǒzhífǎ), meaning The Left Law Administrator. 左執法 (Zuǒzhífǎ), spelled Tso Chih Fa by R.H. Allen, means "the Left-hand Maintainer of Law" 
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