Gamma Virginis

Gamma Virginis (γ Virginis, abbreviated Gamma Vir, γ Vir), officially named Porrima /ˈpɒrɪmə/,[8][9] is a binary star system in the constellation of Virgo. It consists of two almost identical main sequence stars at a distance of about 38 light years.

γ Virginis
Location of γ Virginis (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Virgo
Right ascension 12h 41m 39.64344s[1]
Declination –01° 26′ 57.7421″[1]
Apparent magnitude (V) 2.74 (3.650/3.560[2])
Characteristics
Spectral type F0 V/F0 V[2]
U−B color index -0.05
B−V color index 0.36
Variable type unknown
Astrometry
Radial velocity (Rv)-19.5[3] km/s
Proper motion (μ) RA: –614.76[1] mas/yr
Dec.: 61.34[1] mas/yr
Parallax (π)85.58 ± 0.60[1] mas
Distance38.1 ± 0.3 ly
(11.68 ± 0.08 pc)
Absolute magnitude (MV)2.41[4]
Orbit[5]
CompanionGamma Virginis B
Period (P)168.93 ± 0.30 yr
Semi-major axis (a)3.662 ± 0.013″
Eccentricity (e)0.8825 ± 0.0010
Inclination (i)148.82 ± 0.43°
Longitude of the node (Ω)213.79 ± 0.72°
Periastron epoch (T)2005.438 ± 0.067
Details
Mass1.56[3] M☉
Surface gravity (log g)4.26[3] cgs
Temperature6,757[6] K
Metallicity [Fe/H]–0.07[2] dex
Age1.14[7] Gyr
Other designations
Porrima, Antevorta, Arich, 29 Virginis, BD-00°2601, GCTP 2924.00, Gl 482 AB, HIP 61941, LHS 2604, SAO 138917, WDS 12417-0127
γ Vir A: HD 110379, HR 4825, LFT 937, LTT 4843
γ Vir B: HD 110380, HR 4826, LFT 937, LTT 4844
Database references
SIMBADγ Vir
γ Vir A
γ Vir B

Name

γ Virginis (Latinised to Gamma Virginis) is the star's Bayer designation.

The traditional name Porrima derives from Ancient Rome: Porrima, also known as Antevorta, was one of the Camenae or goddesses of prophecy.[10] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[11] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016[12] included a table of the first two batches of names approved by the WGSN; which included Porrima for this star.

In the catalogue of stars in the Calendarium of Al Achsasi Al Mouakket, this star was designated Laouiyet al Aoua, which was translated into Latin as Angulus Latratoris, meaning 'the angle of the barker'.[13] This star, along with Beta Virginis (Zavijava), Eta Virginis (Zaniah), Delta Virginis (Minelauva) and Epsilon Virginis (Vindemiatrix), were Al ʽAwwāʼ, the Barker.[10]

In Chinese, 太微左垣 (Tài Wēi Zuǒ Yuán), meaning Left Wall of Supreme Palace Enclosure, refers to an asterism consisting of Gamma Virginis, Eta Virginis, Delta Virginis, Epsilon Virginis and Alpha Comae Berenices.[14] Consequently, the Chinese name for Gamma Virginis itself is 太微左垣二 (Tài Wēi Zuǒ Yuán èr, English: the Second Star of Left Wall of Supreme Palace Enclosure.),[15] representing 東上相 (Dōngshǎngxiāng), meaning The First Eastern Minister.[16] 東上相 (Dōngshǎngxiāng), westernized into Shang Seang by R.H. Allen and the meaning is "the High Minister of State".[10]

Properties

Gamma Virginis is a binary star, consisting of two stars of nearly equal apparent magnitudes 3.65 and 3.56, and of spectral type F0V.[2] With an orbital period of 168.93 years,[5][17] it was an easy object for amateur astronomers until the beginning of the 1990s, but in 2011 the smaller apparent distance between the stars requires a larger telescope or special techniques such as speckle interferometry,[5][17] adaptive optics[18] or optical interferometry[19] to resolve the individual components. The last time they were at periapsis was in 1836. The distance will again be wide enough in 2020 to view with a small telescope. The star system has a combined apparent magnitude of 2.9. The system is 39 light years away from the Sun.

Gamma Virginis is 2.8 degrees north of the ecliptic, so it can be occulted by the Moon and (rarely) by planets. In June 2011 Saturn passed a quarter of a degree south of Porrima.

Based upon X-ray emissions—an indicator of the strength of the stellar magnetic field—this system has an estimated age of 1.14 billion years.[7]

Changes of distance and position angle

This table shows the apparent distance between the two stars and their relative position angle: first three columns show data predicted from an orbit calculated in 1937, the next two columns show in 2006,[20] the next three columns show observations reported by the Hanwell Community Observatory.[21]

Predicted from 1937 Strand orbit Predicted from 2006 Docobo orbit Observations 2003 to 2005
Year distance position angle distance position angle Date distance position angle
1995 2.5″ 280 2.25″ 277.6
2000 1.8″ 267 1.50″ 260.9
2002 1.5″ 259 1.13″ 247.5
2003 0.92″ 236.6 2003 Dec. 0.6″ 219°
2004 1.2″ 246 0.68″ 218.4 2004 Dec. 0.4″ 177°
2005 0.44″ 179.8 2005 April 0.27-0.29″ 161±0.6°
2006 0.8″ 221 0.41″ 103.5
2008 0.4″ 126 0.93″ 41.0
2010 0.9″ 44 1.39″ 23.6

References
  1. van Leeuwen, Floor (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752v1, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID 18759600 Note: see VizieR catalogue I/311.
  2. Cayrel de Strobel, G.; Soubiran, C.; Ralite, N. (July 2001), "Catalogue of [Fe/H] determinations for FGK stars: 2001 edition", Astronomy and Astrophysics, 373: 159–163, arXiv:astro-ph/0106438, Bibcode:2001A&A...373..159C, doi:10.1051/0004-6361:20010525, S2CID 17519049
  3. Casagrande, L.; et al. (June 2011), "New constraints on the chemical evolution of the solar neighbourhood and Galactic disc(s). Improved astrophysical parameters for the Geneva-Copenhagen Survey", Astronomy and Astrophysics, 530: A138, arXiv:1103.4651, Bibcode:2011A&A...530A.138C, doi:10.1051/0004-6361/201016276, S2CID 56118016.
  4. Holmberg, J.; et al. (July 2009), "The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics", Astronomy and Astrophysics, 501 (3): 941–947, arXiv:0811.3982, Bibcode:2009A&A...501..941H, doi:10.1051/0004-6361/200811191, S2CID 118577511.
  5. Mason, Brian D.; et al. (2006), "Speckle Interferometry at the US Naval Observatory. XII.", The Astronomical Journal, 132 (5): 2219–2230, Bibcode:2006AJ....132.2219M, doi:10.1086/508231
  6. Muñoz Bermejo, J.; et al. (May 2013), "A PCA approach to stellar effective temperatures", Astronomy and Astrophysics, 453: A95, arXiv:1303.7218, Bibcode:2013A&A...553A..95M, doi:10.1051/0004-6361/201220961, S2CID 67752733.
  7. Vican, Laura (June 2012), "Age Determination for 346 Nearby Stars in the Herschel DEBRIS Survey", The Astronomical Journal, 143 (6): 135, arXiv:1203.1966, Bibcode:2012AJ....143..135V, doi:10.1088/0004-6256/143/6/135, S2CID 118539505
  8. 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.
  9. "IAU Catalog of Star Names". Retrieved 28 July 2016.
  10. Allen, R. H. (1963). Star Names: Their Lore and Meaning (Reprint ed.). New York: Dover Publications Inc. p. 470. ISBN 0-486-21079-0. Retrieved 2010-12-12.
  11. "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
  12. "Bulletin of the IAU Working Group on Star Names, No. 1" (PDF). Retrieved 28 July 2016.
  13. 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: 429–438. Bibcode:1895MNRAS..55..429K. doi:10.1093/mnras/55.8.429.
  14. (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.
  15. (in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 Archived January 30, 2011, at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.
  16. (in 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.
  17. Scardia, M.; Argyle, R. W.; Prieur, J.-L.; Pansecchi, L.; Basso, S.; Law, N. M.; Mackay, C. D. (2007-02-01). "The orbit of the visual binary ADS 8630 (gamma Vir)" (PDF). Astronomische Nachrichten. 328 (2): 146–153. Bibcode:2007AN....328..146S. doi:10.1002/asna.200610710. ISSN 0004-6337.
  18. Riddle, Reed L.; Tokovinin, Andrei; Mason, Brian D.; Hartkopf, William I.; Roberts, Lewis C., Jr.; Baranec, Christoph; Law, Nicholas M.; Bui, Khanh; Burse, Mahesh P. (2015-01-01). "A Survey of the High Order Multiplicity of Nearby Solar-type Binary Stars with Robo-AO". The Astrophysical Journal. 799 (1): 4. arXiv:1411.0682. Bibcode:2015ApJ...799....4R. doi:10.1088/0004-637X/799/1/4. ISSN 0004-637X. S2CID 5642378.
  19. Hutter, D. J.; Zavala, R. T.; Tycner, C.; Benson, J. A.; Hummel, C. A.; Sanborn, J.; Franz, O. G.; Johnston, K. J. (2016-11-01). "Surveying the Bright Stars by Optical Interferometry. I. A Search for Multiplicity among Stars of Spectral Types F-K". The Astrophysical Journal Supplement Series. 227 (1): 4. arXiv:1609.05254. Bibcode:2016ApJS..227....4H. doi:10.3847/0067-0049/227/1/4. ISSN 0067-0049. S2CID 118803592.
  20. "INTERNATIONAL ASTRONOMICAL UNION COMMISSION 26 (DOUBLE STARS)". Archived from the original on 2011-06-15. Retrieved 2010-04-22.
  21. Christopher Taylor, Hanwell Community Observatory
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