Astronomy:Eta Virginis

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Short description: Binary star in the constellation Virgo
η Virginis
(incl. Zaniah)
Virgo constellation map.svg
Red circle.svg
Location of η Virginis (circled)
Observation data
Equinox J2000.0]] (ICRS)
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
Distance265 ± 10 ly
(81 ± 3 pc)
Absolute magnitude (MV)−0.66[5]
Orbit[6]
Primaryη Vir Aa
Companionη 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°
Orbit[6]
Primaryη Vir A
Companionη 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°
Details
η Vir Aa
Mass2.5039 ± 0.1246[7] M☉
Surface gravity (log g)3.0[8] cgs
Temperature9,333[8] K
Metallicity [Fe/H]+0.11[8] dex
Rotational velocity (v sin i)18[9] km/s
η Vir Ab
Mass1.8907 ± 0.0932 M☉
Details[6]
η Vir B
Mass1.66 ± 0.16 M☉
Other designations
Zaniah, 15 Virginis, HR 4689, HD 107259, BD+00°2926, FK5 460, HIP 60129, SAO 138721, CCDM 12199-0040, WDS J12199-0040[10]
Database references
SIMBADdata

Eta Virginis (η Virginis, abbreviated Eta Vir, η Vir) is a triple star system in the zodiac constellation of Virgo. From parallax measurements taken during the Hipparcos mission it is about 265 light-years (81 parsecs) from the Sun. It has a combined apparent visual magnitude of 3.89,[2] bright enough to be seen with the naked eye in dark skies.

The system consists of[11] a binary pair designated Eta Virginis A together with a third companion, Eta Virginis B. A's two components are themselves designated Eta Virginis Aa (officially named Zaniah /ˈzeɪniə/, the traditional name of the system)[12][13] and Ab.

Nomenclature

η Virginis (Latinised to Eta Virginis) is the system's Bayer designation. The designations of the two constituents as Eta Virginis A and those of A'scomponents - Eta Virginis Aa and Ab - derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).[14]

It bore the traditional name Zaniah /zəˈnaɪ.ə/, derived from the Arabic زاوية zāwiyah "corner", the same source as Zavijava (Beta Virginis). In 2016, the IAU organized a Working Group on Star Names (WGSN)[15] to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems.[16] It approved the name Zaniah for the component Eta Virginis Aa on 12 September 2016 and it is now so included in the List of IAU-approved Star Names.[13]

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".[17] This star, along with Beta Virginis (Zavijava), Gamma Virginis (Porrima), Delta Virginis (Minelauva) and Epsilon Virginis (Vindemiatrix), were Al ʽAwwāʼ, "the Barker".[18]

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.[19] Consequently, the Chinese name for Eta Virginis itself is 太微左垣一 (Tài Wēi Zuǒ Yuán yī, English: the First Star of Left Wall of Supreme Palace Enclosure.),[20] representing 左執法 (Zuǒzhífǎ), meaning "The Left Law Administrator".[21] 左執法 (Zuǒzhífǎ), spelled Tso Chih Fa by R.H. Allen, means "the Left-hand Maintainer of Law" [22]

Properties

Eta Virginis looks single, but lunar occultations have shown it to be a very close triple star system consisting of two stars 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 in 72 days. The inclination of this orbit was determined through interferometer observations to be 45.5°, allowing the masses of the two stars to be estimated. The primary star, Eta Virginis Aa, has a mass about 2.5 times the Sun's mass, while the secondary, Eta Virginis Ab, has 1.9 solar masses. The faint tertiary star, Eta Virginis B, orbits the inner group in a wider orbit over a period of 13.1 years.[7]

Eta Virginis is 1.97 degrees north of the ecliptic, so it can be occulted by the Moon and (rarely) by planets. On October 12, 272 BC the ancient Greek astronomer Timocharis observed a conjunction of the star with Venus.[23][24] 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]

Two degrees north-following of Eta Virginis is SS Virginis, a typical Cool Carbon Star and one of the most red colored stars in the equatorial sky.

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, doi:10.1051/0004-6361:20078357, Bibcode: 2007A&A...474..653V 
  2. ↑ 2.0 2.1 2.2 2.3 Cousins, A. W. J. (1984), "Standardization of Broadband Photometry of Equatorial Standards", South African Astronomical Observatory Circulars 8: 59, Bibcode: 1984SAAOC...8...59C 
  3. ↑ 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, doi:10.1086/129336, Bibcode: 1972PASP...84..584L 
  4. ↑ Wilson, Ralph Elmer (1953). "General Catalogue of Stellar Radial Velocities". Carnegie Institute Washington D.C. Publication (Washington: Carnegie Institution of Washington). Bibcode: 1953GCRV..C......0W. 
  5. ↑ Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters 38 (5): 331, doi:10.1134/S1063773712050015, Bibcode: 2012AstL...38..331A. 
  6. ↑ 6.0 6.1 6.2 Hummel, C. A.; Benson, J. A.; Hutter, D. J.; Johnston, K. J.; Mozurkewich, D.; Armstrong, J. T.; Hindsley, R. B.; Gilbreath, G. C. et al. (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. doi:10.1086/374572. Bibcode: 2003AJ....125.2630H. 
  7. ↑ 7.0 7.1 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, doi:10.1088/0004-6256/142/1/6, Bibcode: 2011AJ....142....6B 
  8. ↑ 8.0 8.1 8.2 Wolff, Sidney Carne (October 1967), "A Spectroscopic and Photometric Study of the AP Stars", Astrophysical Journal Supplement 15: 21, doi:10.1086/190162, Bibcode: 1967ApJS...15...21W 
  9. ↑ 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, doi:10.1051/0004-6361:20065224, Bibcode: 2007A&A...463..671R 
  10. ↑ "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 
  11. ↑ "Displaying next number in catalog HIP => 60129". Multiple Star Catalog. http://www.ctio.noao.edu/~atokovin/stars/stars.php?cat=HIP&number=60129. 
  12. ↑ Kunitzsch, Paul; Smart, Tim (2006). A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations (2nd rev. ed.). Cambridge, Massachusetts: Sky Pub. ISBN 978-1-931559-44-7. 
  13. ↑ 13.0 13.1 "Naming Stars". IAU.org. https://www.iau.org/public/themes/naming_stars/. 
  14. ↑ Hessman, F. V.; Dhillon, V. S.; Winget, D. E.; Schreiber, M. R.; Horne, K.; Marsh, T. R.; Guenther, E.; Schwope, A.; Heber, U. (2010). "On the naming convention used for multiple star systems and extrasolar planets". arXiv:1012.0707 [astro-ph.SR].
  15. ↑ IAU Working Group on Star Names (WGSN), International Astronomical Union, https://www.iau.org/science/scientific_bodies/working_groups/280/, retrieved 22 May 2016. 
  16. ↑ "WG Triennial Report (2015-2018) - Star Names". p. 5. https://www.iau.org/static/science/scientific_bodies/working_groups/280/wg-starnames-triennial-report-2015-2018.pdf. 
  17. ↑ 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. doi:10.1093/mnras/55.8.429. Bibcode: 1895MNRAS..55..429K. 
  18. ↑ Allen, R. H. (1963), Star Names: Their Lore and Meaning (Reprint ed.), New York: Dover Publications Inc, p. 469, ISBN 0-486-21079-0, https://archive.org/details/starnamestheirlo00alle/page/469, retrieved 2010-12-12 
  19. ↑ (in 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.
  20. ↑ (in 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.
  21. ↑ (in Chinese) English-Chinese Glossary of Chinese Star Regions, Asterisms and Star Name , Hong Kong Space Museum. Accessed on line November 23, 2010.
  22. ↑ Richard Hinckley Allen: Star Names — Their Lore and Meaning: Virgo
  23. ↑ 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 978-0-387-84825-9, https://books.google.com/books?id=8eaHxE9jUrwC&pg=PA411 
  24. ↑ 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 

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