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)||71.7916 ± 0.0006 days|
|Semi-major axis (a)||0.00736 ± 0.0006"|
|Eccentricity (e)||0.244 ± 0.007|
|Inclination (i)||45.5 ± 0.9°|
|Primary||η Vir A|
|Companion||η Vir B|
|Period (P)||7,896.2 ± 0.2 days|
|Semi-major axis (a)||0.133 ± 0.001"|
|Eccentricity (e)||0.087 ± 0.002|
|Inclination (i)||50.6 ± 0.1°|
|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☉|
|η Vir B|
|Mass||1.66 ± 0.16 M☉|
Eta Virginis (η Virginis, abbreviated Eta Vir, η Vir), also named Zaniah, is a multiple star system in the zodiac constellation of Virgo. From parallax measurements, it was found to be roughly 265 light-years (81 parsecs) from the Sun. 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.
It bore the traditional name Zaniah //, derived from the Arabic زاوية zāwiyah "corner", the same source as Zavijava (Beta Virginis). In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN approved the name Zaniah for this star on 12 September 2016 and it is now so entered in the IAU Catalog of Star Names.
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 Beta Virginis (Zavijava), Gamma Virginis (Porrima), Delta Virginis (Auva) and Epsilon Virginis (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 Eta Virginis, Gamma Virginis, Delta Virginis, Epsilon Virginis and Alpha Comae Berenices. Consequently, Eta 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" 
Although Eta Virginis looks single, lunar occultations have shown this star to be a very close triple star system consisting of two stars only 0.6 AU apart, assuming a distance of 91 parsecs, 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, Eta Vir Aa, has a mass of about 2.5 times the Sun's mass, while the secondary, Eta Vir Ab, has 1.9 solar masses. The faint tertiary star, Eta Vir B, orbits the inner group in a wider orbit over a period of 13.1 years.
Because Eta Virginis 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.
- van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv: , Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357
- Cousins, A. W. J. (1984), "Standardization of Broadband Photometry of Equatorial Standards", South African Astronomical Observatory Circulars, 8: 59, Bibcode:1984SAAOC...8...59C
- Levato, O. H. (August 1972), "Rotational Velocities and Spectral Types of Some A-Type Stars", Publications of the Astronomical Society of the Pacific, 84 (500): 584, Bibcode:1972PASP...84..584L, doi:10.1086/129336
- Wilson, Ralph Elmer (1953). General Catalogue of Stellar Radial Velocities. Washington: Carnegie Institution of Washington. Bibcode:1953GCRV..C......0W.
- Hummel, C. A.; Benson, J. A.; Hutter, D. J.; Johnston, K. J.; Mozurkewich, D.; Armstrong, J. T.; Hindsley, R. B.; Gilbreath, G. C.; Rickard, L. J.; White, N. M. (2003). "First Observations with a Co-phased Six-Station Optical Long-Baseline Array: Application to the Triple Star η Virginis". The Astronomical Journal. 125 (5): 2630. Bibcode:2003AJ....125.2630H. doi:10.1086/374572.
- Behr, Bradford B.; et al. (July 2011), "Stellar Astrophysics with a Dispersed Fourier Transform Spectrograph. II. Orbits of Double-lined Spectroscopic Binaries", The Astronomical Journal, 142 (1): 6, arXiv: , Bibcode:2011AJ....142....6B, doi:10.1088/0004-6256/142/1/6
- Wolff, Sidney Carne (October 1967), "A Spectroscopic and Photometric Study of the AP Stars", Astrophysical Journal Supplement, 15: 21, Bibcode:1967ApJS...15...21W, doi:10.1086/190162
- Royer, F.; Zorec, J.; Gómez, A. E. (February 2007), "Rotational velocities of A-type stars. III. Velocity distributions", Astronomy and Astrophysics, 463 (2): 671–682, arXiv: , Bibcode:2007A&A...463..671R, doi:10.1051/0004-6361:20065224
- "eta Vir -- Spectroscopic binary", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2012-01-06
- "IAU Catalog of Star Names". Retrieved 28 July 2016.
- IAU Working Group on Star Names (WGSN), International Astronomical Union, retrieved 22 May 2016.
- Knobel, E. B. (June 1895). "Al Achsasi Al Mouakket, on a catalogue of stars in the Calendarium of Mohammad Al Achsasi Al Mouakket". Monthly Notices of the Royal Astronomical Society. 55 (8): 429. Bibcode:1895MNRAS..55..429K. doi:10.1093/mnras/55.8.429.
- Allen, R. H. (1963), Star Names: Their Lore and Meaning (Reprint ed.), New York: Dover Publications Inc, p. 469, ISBN 0-486-21079-0, retrieved 2010-12-12
- (Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
- (Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 Archived August 19, 2010, at the Wayback Machine., Hong Kong Space Museum. Accessed on line November 23, 2010.
- (Chinese) English-Chinese Glossary of Chinese Star Regions, Asterisms and Star Name Archived August 10, 2010, at the Wayback Machine., Hong Kong Space Museum. Accessed on line November 23, 2010.
- Richard Hinckley Allen: Star Names — Their Lore and Meaning: Virgo
- Pedersen, Olaf (2010), Jones, Alexander, ed., A Survey of the Almagest: With Annotation and New Commentary by Alexander Jones, Sources and Studies in the History of Mathematics and Physical Sciences (2nd ed.), Springer, p. 411, ISBN 0-387-84825-8
- Fomenko, A. T.; Vi︠a︡cheslavovich, Vladimir Kalashnikov; Nosovskiĭ, Gleb Vladimirovich (1993), Geometrical and statistical methods of analysis of star configurations: dating Ptolemy's Almagest, CRC Press, p. 215, ISBN 0-8493-4483-2