Delta Herculis

Delta Herculis (δ Herculis, abbreviated Delta Her, δ Her) is a multiple star system in the constellation of Hercules. Its light produces to us apparent magnitude 3.12, as such the third-brightest star in the large, fairly dim constellation. Based on parallax measurement taken during the Hipparcos mission, it is approximately 23.1 parsecs (75 light-years) from the Sun.

δ Herculis
Location of δ Herculis (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Hercules
Right ascension 17h 15m 01.9106s[1]
Declination 24° 50′ 21.135″[1]
Apparent magnitude (V) 3.126[1]
Characteristics
Spectral type A3IV[1]
U−B color index +0.7[2]
B−V color index +0.08[2]
Astrometry
Radial velocity (Rv)−40.0[1] km/s
Proper motion (μ) RA: -21.14[1] mas/yr
Dec.: -157.68[1] mas/yr
Parallax (π)43.41 ± 0.15 mas[3]
Distance75.1 ± 0.3 ly
(23.04 ± 0.08 pc)
Absolute magnitude (MV)+1.31[4]
Details
Mass2.4[5] M☉
Radius2.2[5] R☉
Luminosity38[5] L☉
Temperature9,620 ± 350[5] K
Rotational velocity (v sin i)270[6] km/s
Age370[6] Myr
Other designations
Sarin, δ Her, 65 Her, BD 25° 3221, CCDM J17151+2451A, FK5 641, GC 23294, HD 156164, HIP 84379, HR 6410, SAO 84951.
Database references
SIMBADdata

Components

It consists of a binary pair, designated Delta Herculis A, together with three potential companions, suffixed B, C and D. Furthermore B is believed to be an optical binary.[7] A's components are designated Delta Herculis Aa (officially named Sarin /ˈsɛərɪn/, the traditional name of the system)[8] and Ab. The angular separation between the main component A and the component B, which has a magnitude of 8.74, is 8.5 arcseconds .

Nomenclature

δ Herculis (Latinised to Delta Herculis) is the system's Bayer designation. The designations of the four constituents as Delta Herculis A, B, C and D, and those of A's components - Delta Herculis 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).[9]

It bore the traditional name Sarin.[10][11] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[12] to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems.[13] It approved the name Sarin for the component Delta Herculis Aa on 12 September 2016 and it is now so included in the List of IAU-approved Star Names.[8]

In the catalogue of stars in the Calendarium of Al Achsasi al Mouakket, this star was designated Menkib al Jathi al Aisr, which was translated into Latin as Humerus Sinister Ingeniculi, meaning kneeler's left shoulder.[14]

In Chinese, 天市左垣 (Tiān Shì Zuǒ Yuán), meaning Left Wall of Heavenly Market Enclosure, refers to an asterism which represents eleven old states in China which is marking the left borderline of the enclosure, consisting of Delta Herculis, Lambda Herculis, Mu Herculis, Omicron Herculis, 112 Herculis, Zeta Aquilae, Theta1 Serpentis, Eta Serpentis, Nu Ophiuchi, Xi Serpentis and Eta Ophiuchi.[15] Consequently, the Chinese name for Delta Herculis itself is 天市左垣一 (Tiān Shì Zuǒ Yuán yī, English: the First Star of Left Wall of Heavenly Market Enclosure), and represents the state of Wei (魏),[16][17] together with 33 Capricorni, according to Ian Ridpath version[18] or Phi Capricorni and Chi Capricorni in R.H. Allen's version[19] in Twelve States (asterism).

Properties

Delta Herculis A presents as an A-type main-sequence subgiant with a stellar classification of A3IV. It has both a mass and radius that are roughly two times solar yielding a total luminosity of about 18.5 L☉[6]

See also

References
  1. "del Her -- Star in double system", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2010-11-17
  2. Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data, SIMBAD, Bibcode:1986EgUBV........0M
  3. van Leeuwen, F. (November 2007). "Hipparcos, the New Reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600.
  4. Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.
  5. Malagnini, M. L.; Morossi, C. (November 1990), "Accurate absolute luminosities, effective temperatures, radii, masses and surface gravities for a selected sample of field stars", Astronomy and Astrophysics Supplement Series, 85 (3): 1015–1019, Bibcode:1990A&AS...85.1015M
  6. Kaler, James B., "DELTA HER (Delta Herculis)", Stars, University of Illinois, retrieved 2010-11-17
  7. "Washington Double Star Catalog". United States Naval Observatory. Archived from the original on 14 February 2011. Retrieved 2 January 2018.
  8. "Naming Stars". IAU.org. Retrieved 16 December 2017.
  9. 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].
  10. Vonnegut, Kurt, Constellations: Hercules 'the Strongman', The BBC (British Broadcasting Corporation), retrieved 2010-11-17
  11. δ Her (Sarin), Wikisky.org, retrieved 2010-11-17
  12. IAU Working Group on Star Names (WGSN), International Astronomical Union, retrieved 22 May 2016.
  13. "WG Triennial Report (2015-2018) - Star Names" (PDF). p. 5. Retrieved 2018-07-14.
  14. 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, doi:10.1093/mnras/55.8.429
  15. (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.
  16. (in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 Archived September 29, 2009, at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.
  17. (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.
  18. Ian Ridpath's Startales - Capricornus the Sea Goat
  19. Star Names - R.H.Allen p.142
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