Delta Sagittarii

Delta Sagittarii (δ Sagittarii, abbreviated Delta Sgr, δ Sgr), formally named Kaus Media /ˌkɔːs ˈmiːdiə/,[10][11] is a double star[9] in the southern zodiac constellation of Sagittarius. The apparent visual magnitude of this star is +2.70,[2] making it easily visible to the naked eye. Parallax measurements place the distance at roughly 348 light-years (107 parsecs) from the Sun.[1]

Delta Sagittarii
Location of δ Sagittarii (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Sagittarius
Right ascension  18h 20m 59.64354s[1]
Declination −29° 49′ 41.1659″[1]
Apparent magnitude (V) +2.70[2]
Characteristics
Spectral type K3 III[3]
U−B color index +1.55[2]
B−V color index +1.38[2]
Astrometry
Radial velocity (Rv)–19.9[4] km/s
Proper motion (μ) RA: +32.54[1] mas/yr
Dec.: −25.57[1] mas/yr
Parallax (π)9.38 ± 0.18[1] mas
Distance348 ± 7 ly
(107 ± 2 pc)
Absolute magnitude (MV)−1.99[5]
Details
δ Sgr A
Mass3.21[6] M☉
Radius16[7] R☉
Surface gravity (log g)0.30[8] cgs
Temperature4,203±69[6] K
Metallicity [Fe/H]−0.32[8] dex
Age260[6] Myr
Other designations
Kaus Media, Media, δ Sgr, CPD−30° 5513, FK5 687, GC 25024, HD 168454, HIP 89931, HR 6859, SAO 186681, PPM 268275, CCDM J18210-2950A, WDS J18210-2950A[9]
Database references
SIMBADdata

Properties

Eggleton and Tokovinin (2008) list Delta Sagittarii as a binary star system consisting of an evolved K-type giant star with a stellar classification of K3 III,[3] and a white dwarf companion.[12] The giant is a weak barium star, most likely having had its surface abundance of s-process elements enhanced through mass transfer from its orbiting companion.[13] It has an estimated 3.21 times the mass of the Sun and is about 260 million years old.[6]

Delta Sagittarii has three dim visual companions:[14]

  • a 14th magnitude star at a separation of 26 arcseconds,
  • a 15th magnitude star at a separation of 40 arcseconds, and
  • a 13th magnitude star at a separation of 58 arcseconds from the primary.

Nomenclature

δ Sagittarii (Latinised to Delta Sagittarii) is the star's Bayer designation.

It bore the traditional names Kaus Media, Kaus Meridionalis, and Media, which derive from the Arabic قوس (qaws, meaning "bow") and Latin media (meaning "middle"). In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[15] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016[16] included a table of the first two batches of names approved by the WGSN; which included Kaus Media for this star.

In the catalogue of stars in the Calendarium of Al Achsasi al Mouakket, this star was designated Thani al Waridah, meaning 'second of Warida'.[17]

In Chinese, 箕 (Jī), meaning Winnowing Basket, refers to an asterism consisting of Delta Sagittarii, Gamma Sagittarii, Epsilon Sagittarii and Eta Sagittarii. Consequently, the Chinese name for Delta Sagittarii itself is 箕宿二 (Jī Sù èr, English: the Second Star of Winnowing Basket.)[18]

This star, together with Gamma Sagittarii, Epsilon Sagittarii, Zeta Sagittarii, Lambda Sagittarii, Sigma Sagittarii, Tau Sagittarii and Phi Sagittarii, comprise the asterism 'Teapot'.[19]

In the Hindu system of astrology, this star is also called Purvashada Nakshatra.

See also
  • Delta Sagittarii in fiction

References
  1. van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357
  2. Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99): 99, Bibcode:1966CoLPL...4...99J
  3. Houk, Nancy (1979), "Michigan catalogue of two-dimensional spectral types for the HD stars", Michigan Catalogue of Two-dimensional Spectral Types for the HD stars. Volume_3. Declinations -40_ƒ0 to -26_ƒ0, Ann Arbor, Michigan: Dept. of Astronomy, University of Michigan, 3, Bibcode:1982mcts.book.....H
  4. Evans, D. S. (June 20–24, 1966), Batten, Alan Henry; Heard, John Frederick (eds.), "The Revision of the General Catalogue of Radial Velocities", Determination of Radial Velocities and their Applications, University of Toronto: International Astronomical Union, 30: 57, Bibcode:1967IAUS...30...57E
  5. Elgarøy, Øystein; Engvold, Oddbjørn; Lund, Niels (March 1999), "The Wilson-Bappu effect of the MgII K line - dependence on stellar temperature, activity and metallicity", Astronomy and Astrophysics, 343: 222–228, Bibcode:1999A&A...343..222E
  6. Luck, R. Earle (2015), "Abundances in the Local Region. I. G and K Giants", The Astronomical Journal, 150 (3): 88, arXiv:1507.01466, Bibcode:2015AJ....150...88L, doi:10.1088/0004-6256/150/3/88.
  7. Pasinetti Fracassini, L. E.; et al. (February 2001), "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS)", Astronomy and Astrophysics (Third ed.), 367: 521–524, arXiv:astro-ph/0012289, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451.
  8. Luck, R. Earle; Challener, Sharon L. (December 1995), "Chemical Abundances for Very Strong-Lined Giants", Astronomical Journal, 110: 2968, Bibcode:1995AJ....110.2968L, doi:10.1086/117741.
  9. "del Sgr -- Star in double system", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2012-01-11
  10. 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.
  11. "IAU Catalog of Star Names". Retrieved 28 July 2016.
  12. Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x.
  13. Gomez, A. E.; et al. (1997), "Absolute magnitudes and kinematics of barium stars", Astronomy and Astrophysics, 319: 881, Bibcode:1997A&A...319..881G.
  14. Dommanget, J.; Nys, O. (1994). "Catalogue des composantes d'etoiles doubles et multiples (CCDM) premiere edition - Catalogue of the components of double and multiple stars (CCDM) first edition". Com. de l'Observ. Royal de Belgique. 115: 1. Bibcode:1994CoORB.115....1D.
  15. "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
  16. "Bulletin of the IAU Working Group on Star Names, No. 1" (PDF). Retrieved 28 July 2016.
  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): 435. Bibcode:1895MNRAS..55..429K. doi:10.1093/mnras/55.8.429.
  18. (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 5 月 11 日
  19. "Teapot". constellation-guide.com. Retrieved 2017-05-13.
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