View source for Delta Sagittarii

{{short description|Double binary star in the constellation Sagittarius}}
{{Starbox begin
| name = Delta Sagittarii
}}
{{Starbox image
| image = 
{{Location mark
|image=Sagittarius IAU.svg|alt=Diagram showing star positions and boundaries of the Sagittarius constellation and its surroundings|float=center|width=200
|position=right
|mark=Red circle.svg|mark_width=10|mark_link=δ Sagittarii
|x=655|y=583
}}
| caption=Location of δ Sagittarii (circled)
}}
{{Starbox observe
| epoch    = [[J2000.0]]
| ra       = {{RA|18|20|59.64354}}<ref name=Leeuwen/>
| dec      = {{DEC|-29|49|41.1659}}<ref name=Leeuwen/>
| appmag_v = +2.70<ref name=Johnson/>
| constell = [[Sagittarius (constellation)|Sagittarius]]
}}
{{Starbox character
| class    = K3&nbsp;III<ref name=Houk1979/>
| b-v      = +1.38<ref name=Johnson/>
| u-b      = +1.55<ref name=Johnson/>
| variable = 
}}
{{Starbox astrometry
| radial_v = –19.9<ref name=rgcrv/>
| prop_mo_ra  = +32.54<ref name=Leeuwen/>
| prop_mo_dec = −25.57<ref name=Leeuwen/>
| parallax = 9.38
| p_error  = 0.18
| parallax_footnote = <ref name=Leeuwen/>
| absmag_v = −1.99<ref name=Elgaroy/>
}}
{{Starbox detail
| component1 = δ Sgr A
| mass     = 3.21<ref name=Luck2015/>
| radius   = {{Solar radius calculator|type=logLT|3.22|4203|decimals=2}}<ref name=Luck2015/>{{Efn|name=radius}}
| luminosity  = 1,660<ref name=Luck2015/>
| temperature = {{Val|4203|69|fmt=commas}}<ref name=Luck2015/>
| gravity  = 0.30<ref name=Luck1995/>
| metal_fe = −0.32<ref name=Luck1995/>
| rotational_velocity = 3.6<ref name=deMederios2014/>
| age_myr  = 260<ref name=Luck2015/>
}}
{{Starbox catalog
| names = {{odlist|name=Kaus Media|name2=Kaus Meridionalis|name3=Media|B=δ&nbsp;Sgr|CPD=−30°5513|FK5=687|HD=168454|HIP=89931|HR=6859|SAO=186681|WDS=J18210-2950A|CCDM=J18210-2950A|GC=25024|IDS=18146-2952 A|PPM=268275}}<ref name=SIMBAD/>
}}
{{Starbox reference|Simbad=del+Sgr|sn=Delta Sagittarii}}
{{Starbox end}}

'''Delta Sagittarii''' ('''δ&nbsp;Sagittarii''', abbreviated '''Delta&nbsp;Sgr''', '''δ&nbsp;Sgr'''), formally named '''Kaus Media''' {{IPAc-en|,|k|ɔː|s|_|'|m|iː|d|i|ə}},<ref name=Kunitzsch/><ref name="IAU-CSN"/> is a star in the southern [[zodiac]] [[constellation]] of [[Sagittarius (constellation)|Sagittarius]]. The [[apparent visual magnitude]] of this star is +2.70,<ref name=Johnson/> making it [[Bortle Dark-Sky Scale|easily visible]] to the naked eye. [[Parallax]] measurements place the distance at roughly {{Convert|348|ly|pc|abbr=off|lk=on}} from the [[Sun]].<ref name=Leeuwen/>

==Properties==

Eggleton and Tokovinin (2008) list Delta Sagittarii as a [[binary star]] system consisting of an [[stellar evolution|evolved]] [[K-type star|K-type]] [[giant star]] with a [[stellar classification]] of K3&nbsp;III,<ref name=Houk1979/> and a [[white dwarf]] companion.<ref name=Eggleton/> The giant has an estimated mass three times that of the Sun, and is most likely fusing helium to carbon in its core.<ref>{{Cite web |title=Kaus Media |url=http://stars.astro.illinois.edu/sow/kausmed.html |access-date=2024-08-04 |website=stars.astro.illinois.edu}}</ref> It is a weak [[barium star]], most likely having had its surface abundance of [[s-process]] elements enhanced through mass transfer from an orbiting companion, presumed to be a white dwarf.<ref name=Gomez/> It has an estimated 3.21 times the [[mass of the Sun]] and is about 260{{nbsp}}million years old.<ref name=Luck2015/>

Delta Sagittarii has three dim visual companions:<ref name=ccdm/>
* a 14th magnitude star at a separation of 26 [[arcsecond]]s,
* 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&nbsp;Sagittarii'' ([[Latinisation of names|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 {{langx|ar|قوس|rtl=yes}} {{lang|ar-Latn|qaws}} ('bow') and {{langx|la|media}} ('middle'). In 2016, the [[International Astronomical Union]] organized a [[Working Group on Star Names]] (WGSN)<ref name=WGSN/> to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016<ref name=WGSN1/> 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 {{lang|ar-Latn|Thani al Waridah}}, meaning 'second of [[Warida]]'.<ref name=Knobel1895/>

In [[Chinese astronomy]], {{lang|zh|箕}} {{lang|zh-Latn|Jī}} ('[[Winnowing Basket (Chinese constellation)|Winnowing Basket]]') refers to an asterism consisting of Delta Sagittarii, [[Gamma2 Sagittarii|Gamma<sup>2</sup> Sagittarii]], [[Epsilon Sagittarii]] and [[Eta Sagittarii]]. Consequently, the [[Chinese star names|Chinese name]] for Delta Sagittarii itself is {{lang|zh|箕宿二}} {{lang|zh-Latn|Jī Sù èr}} ('the Second Star of Winnowing Basket').<ref name=aeea/>

This star, together with Gamma Sagittarii, Epsilon Sagittarii, [[Zeta Sagittarii]], [[Lambda Sagittarii]], [[Sigma Sagittarii]], [[Tau Sagittarii]] and [[Phi Sagittarii]], comprises the [[Teapot (asterism)|Teapot]] [[Asterism (astronomy)|asterism]].<ref name=teapot/>
 
In [[Hindu astrology]], this star is also called {{lang|sa-Latn|Purvashada Nakshatra}}.

==Notes==
{{notelist|notes=

{{Efn|name=radius|1=Calculated, using the [[Stefan-Boltzmann law]] and the star's [[effective temperature]] and luminosity, with respect to the [[Sun|solar]] nominal effective temperature of 5,772&nbsp;[[Kelvin|K]]:<math display="block">\sqrt{\biggl(\frac{5,772}{4,203}\biggr)^4 \cdot 10^{3.22}} = 76.83\ R_\odot.</math>}}

}}

==References==
{{reflist|refs=

<ref name=deMederios2014>{{cite journal |last1=De Medeiros |first1=J. R. |last2=Alves |first2=S. |last3=Udry |first3=S. |last4=Andersen |first4=J. |last5=Nordström |first5=B. |last6=Mayor |first6=M. |title=A catalog of rotational and radial velocities for evolved stars: V. Southern stars⋆⋆⋆ |journal=Astronomy & Astrophysics |date=January 2014 |volume=561 |pages=A126 |doi=10.1051/0004-6361/201220762 |issn=0004-6361 |bibcode=2014A&A...561A.126D |arxiv=1312.3474|doi-access=free}}</ref>

<ref name=WGSN1>{{cite web|url=http://www.pas.rochester.edu/~emamajek/WGSN/WGSN_bulletin1.pdf|title=Bulletin of the IAU Working Group on Star Names|number=1|date=July 2016|access-date=28 July 2016|url-status=live|archive-url=https://web.archive.org/web/20160909203812/http://www.pas.rochester.edu/~emamajek/WGSN/WGSN_bulletin1.pdf|archive-date=2016-09-09}}</ref>

<ref name=Knobel1895>{{cite journal|last=Knobel|first=E. B.|title=Al Achsasi Al Mouakket, on a catalogue of stars in the Calendarium of Mohammad Al Achsasi Al Mouakket|journal=[[Monthly Notices of the Royal Astronomical Society]]|volume=55|issue=8|page=435|date=June 1895|bibcode=1895MNRAS..55..429K|doi=10.1093/mnras/55.8.429|doi-access=free}}</ref>

<ref name=aeea>{{cite web|url=http://aeea.nmns.edu.tw/2006/0605/ap060511.html|title=中國古代的星象系統 (11): 箕宿|author=陳輝樺|website=AEEA 天文教育資訊網|trans-website=AEEA (Activities of Exhibition and Education in Astronomy)|date=11 May 2006|publisher=[[National Museum of Natural Science]]|language=zh|url-status=live|archive-url=https://web.archive.org/web/20201003025901/http://aeea.nmns.edu.tw/2006/0605/ap060511.html|archive-date=2020-10-03}}</ref>

<ref name=teapot>{{cite web|title=Teapot|date=25 August 2015|website=Constellation Guide|url=http://www.constellation-guide.com/teapot/|access-date=2017-05-13|url-status=live|archive-url=https://web.archive.org/web/20200726122820/https://www.constellation-guide.com/teapot/|archive-date=2020-07-26}}</ref>

<ref name=WGSN>{{cite web|url=https://www.iau.org/science/scientific_bodies/working_groups/280/|title=Division C WG Star Names|publisher=[[International Astronomical Union]]|access-date=22 May 2016|url-status=live|archive-url=https://web.archive.org/web/20160610172014/https://www.iau.org/science/scientific_bodies/working_groups/280/|archive-date=2016-06-10}}</ref>

<ref name=ccdm>{{cite journal|bibcode=1994CoORB.115....1D|title=Catalogue des composantes d'etoiles doubles et multiples (CCDM) premiere edition – Catalogue of the components of double and multiple stars (CCDM)|edition=First|journal=Communications de l'Observatoire Royal de Belgique|publisher=[[Observatoire Royal de Belgique]]|volume=115|pages=1|last1=Dommanget|first1=J.|last2=Nys|first2=O.|year=1994}}</ref>

<ref name="IAU-CSN">{{cite web|url=http://www.pas.rochester.edu/~emamajek/WGSN/IAU-CSN.txt|title=IAU Catalog of Star Names|access-date=28 July 2016|url-status=live|format=TXT|archive-url=https://web.archive.org/web/20160812092144/http://www.pas.rochester.edu/~emamajek/WGSN/IAU-CSN.txt|archive-date=2016-08-12}}</ref>

<ref name=Kunitzsch>{{cite book|last1=Kunitzsch|first1=P.|last2=Smart|first2=T.|year=2006|title=A Dictionary of Modern Star Names: A short guide to 254 star names and their derivations|edition=2nd revised|page=22|publisher=Sky Publishing|isbn=1-931559-44-9}}</ref>

<ref name=Gomez>{{cite journal|title=Absolute magnitudes and kinematics of barium stars|journal=[[Astronomy and Astrophysics]]|last1=Gomez|first1=A. E.|last2=Luri|first2=X.|last3=Grenier|first3=S.|last4=Prevot|first4=L.|last5=Mennessier|first5=M. O.|last6=Figueras|first6=F.|last7=Torra|first7=J.|volume=319|pages=881–885|date=March 1997|bibcode=1997A&A...319..881G|bibcode-access=free}}</ref>

<ref name=Eggleton>{{cite journal|last1=Eggleton|first1=P. P.|last2=Tokovinin|first2=A. A.|title=A catalogue of multiplicity among bright stellar systems|journal=[[Monthly Notices of the Royal Astronomical Society]]|volume=389|issue=2|pages=869–879|date=September 2008|doi=10.1111/j.1365-2966.2008.13596.x|bibcode=2008MNRAS.389..869E|arxiv=0806.2878|s2cid=14878976|doi-access=free}}</ref>

<!-- <ref name=Fracassini2001>{{cite journal|last1=Pasinetti Fracassini|first1=L. E.|last2=Pastori|first2=L.|last3=Covino|first3=S.|last4=Pozzi|first4=A.|title=Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS)|edition=Third|journal=[[Astronomy and Astrophysics]]|volume=367|number=2|pages=521–524|date=15 February 2001|doi=10.1051/0004-6361:20000451|bibcode=2001A&A...367..521P|arxiv=astro-ph/0012289|doi-access=free}}</ref> -->

<ref name=Luck2015>{{cite journal|title=Abundances in the Local Region. I. G and K Giants|journal=[[The Astronomical Journal]]|last=Luck|first=R. Earle|volume=150|number=3|page=88|date=25 August 2015|bibcode=2015AJ....150...88L|doi=10.1088/0004-6256/150/3/88|arxiv=1507.01466|doi-access=free}}</ref>

<ref name=Luck1995>{{cite journal|last1=Luck|first1=R. Earle|last2=Challener|first2=Sharon L.|title=Chemical Abundances for Very Strong-Lined Giants|journal=[[The Astronomical Journal]]|volume=110|number=6|pages=2968–3009|date=December 1995|doi=10.1086/117741|bibcode=1995AJ....110.2968L|doi-access=free}}</ref>

<ref name=Leeuwen>{{cite journal|first=F.|last=van Leeuwen|date=November 2007|title=Validation of the new Hipparcos reduction|journal=[[Astronomy and Astrophysics]]|volume=474|number=2|pages=653–664|bibcode=2007A&A...474..653V|doi=10.1051/0004-6361:20078357|arxiv=0708.1752|doi-access=free}}</ref>

<ref name=Houk1979>{{cite book|title=Michigan Catalogue of Two-dimensional Spectral Types for the HD stars: Declinations -40_ƒ0 to -26_ƒ0|volume=3|last=Houk|first=Nancy|location=Ann Arbor, MI|department=Astronomy|publisher=University of Michigan|year=1982|bibcode=1982mcts.book.....H}}</ref>

<ref name=rgcrv>{{cite conference|last=Evans|first=D. S.|year=1967|conference=International Astronomical Union Symposium no. 30|conference-url=https://www.iau.org/science/meetings/past/symposia/|editor1-last=Batten|editor1-first=Alan Henry|editor2-last=Heard|editor2-first=John Frederick|title=The Revision of the General Catalogue of Radial Velocities: Determination of Radial Velocities and their Applications|volume=30|pages=57|location=University of Toronto|publication-place=London|publisher=Academic Press|bibcode=1967IAUS...30...57E}}</ref>

<ref name=Johnson>{{cite journal|last1=Johnson|first1=H. L.|last2=Iriarte|first2=B.|last3=Mitchell|first3=R. I.|last4=Wisniewskj|first4=W. Z.|title=UBVRIJKL photometry of the bright stars|journal=[[Communications of the Lunar and Planetary Laboratory]]|volume=4|issue=1|pages=99–110|year=1966|bibcode=1966CoLPL...4...99J|bibcode-access=free}}</ref>

<ref name=SIMBAD>{{cite SIMBAD|title=del Sgr|access-date=2012-01-11}}</ref>

<ref name=Elgaroy>{{cite journal|last1=Elgarøy|first1=Øystein|last2=Engvold|first2=Oddbjørn|last3=Lund|first3=Niels|title=The Wilson-Bappu effect of the MgII K line – dependence on stellar temperature, activity and metallicity|journal=[[Astronomy and Astrophysics]]|volume=343|pages=222–228|date=March 1999|bibcode=1999A&A...343..222E|bibcode-access=free}}</ref>

}}
*

{{Stars of Sagittarius}}

{{DEFAULTSORT:Delta Sagittarii}}
[[Category:K-type giants]]
[[Category:Barium stars]]
[[Category:Binary stars]]
[[Category:Bayer objects|Sagittarii, Delta]]
[[Category:Sagittarius (constellation)]]
[[Category:Stars with proper names|Kaus Media]]
[[Category:Flamsteed objects|Sagittarii, 19]]
[[Category:Hipparcos objects|089931]]
[[Category:Bright Star Catalogue objects|6859]]
[[Category:Henry Draper Catalogue objects|168454]]
[[Category:Durchmusterung objects]]
[[Category:White dwarfs]]