Eta Virginis
 Location of η Virginis (circled) |
|
| Observation data Epoch J2000 Equinox J2000 |
|
|---|---|
| Constellation | Virgo |
| Right ascension | 12h 19m 54.35783s[1] |
| Declination | –00° 40′ 00.5095″[1] |
| Apparent magnitude (V) | 3.890[2] |
| Characteristics | |
| Spectral type | A2 V[3] |
| U−B color index | +0.055[2] |
| B−V color index | +0.029[2] |
| Astrometry | |
| Radial velocity (Rv) | +2.3[4] km/s |
| Proper motion (μ) | RA: –57.58[1] mas/yr Dec.: –25.19[1] mas/yr |
| Parallax (π) | 12.29 ± 0.45[1] mas |
| Distance | 265 ± 10 ly (81 ± 3 pc) |
| Orbit[5] | |
| 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) (secondary) |
197.21 ± 1.74° |
| Semi-amplitude (K1) (primary) |
26.606 ± 0.198 km/s |
| Semi-amplitude (K2) (secondary) |
35.236 ± 0.273 km/s |
| Details | |
| η Vir Aa | |
| Mass | 2.5039 ± 0.1246[5] M☉ |
| Surface gravity (log g) | 3.0[6] |
| Temperature | 9,333[6] K |
| Metallicity [Fe/H] | +0.11[6] dex |
| Rotational velocity (v sin i) | 18[7] km/s |
| η Vir Ab | |
| Mass | 1.8907 ± 0.0932 M☉ |
| Other designations | |
Eta Virginis (η Vir, η Virginis) is a multiple star system in the zodiac constellation of Virgo. It has the traditional name Zaniah 
/zəˈnaɪ.ə/. 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,[2] which is bright enough for the system to be seen with the naked eye in dark skies.
Although the star looks single in any telescope, 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.[citation needed] 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.[5]
Because Zaniah is near the ecliptic, it can be occulted by the Moon and (very rarely) by planets. On September 1, 329 BC, the ancient Greek astronomer Timocharis observed the star being passed by Venus, when the planet came within an arcminute of it.[9] The last occultation by a planet took place on September 27, 1843, also by Venus, which will occult it again on November 19, 2445.[citation needed]
[edit] Etymology
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.[10] This star, along with β Vir(Zavijava), γ Vir (Porrima), δ Vir (Auva) and ε Vir (Vindemiatrix), were Al ʽAwwāʼ, the Barker.[11]
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.[12] 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.)[13], representing 左執法 (Zuǒzhífǎ), meaning The Left Law Administrator[14]. 左執法 (Zuǒzhífǎ), westernized into Tso Chih Fa by R.H. Allen and the meaning is "the Left-hand Maintainer of Law" [15]
[edit] References
- ^ a b c d e van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, Bibcode 2007A&A...474..653V, doi:10.1051/0004-6361:20078357
- ^ a b c d 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 1953QB901.W495......
- ^ a b c 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, Bibcode 2011AJ....142....6B, doi:10.1088/0004-6256/142/1/6
- ^ a b c 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, Bibcode 2007A&A...463..671R, doi:10.1051/0004-6361:20065224
- ^ "eta Vir -- Spectroscopic binary", SIMBAD (Centre de Données astronomiques de Strasbourg), http://simbad.u-strasbg.fr/simbad/sim-id?Ident=Eta+Virginis, retrieved 2012-01-06
- ^ 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 0849344832
- ^ 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: 429. Bibcode 1895MNRAS..55..429K.
- ^ Allen, R. H. (1963), Star Names: Their Lore and Meaning (Reprint ed.), New York: Dover Publications Inc, p. 469, ISBN 0486210790, http://penelope.uchicago.edu/Thayer/E/Gazetteer/Topics/astronomy/_Texts/secondary/ALLSTA/Virgo*.html, 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 9789867332257.
- ^ (Chinese) 香港太空館 - 研究資源 - 亮星中英對照表, Hong Kong Space Museum. Accessed on line November 23, 2010.
- ^ (Chinese) English-Chinese Glossary of Chinese Star Regions, Asterisms and Star Name, Hong Kong Space Museum. Accessed on line November 23, 2010.
- ^ Richard Hinckley Allen: Star Names — Their Lore and Meaning: Virgo
