Alpha Sagittae
{{Short description|Star in the constellation Sagitta}}
{{Starbox begin
| name = α Sagittae
}}
{{Starbox image
| image=
{{Location mark
|image=Sagitta constellation map.svg|alt=|float=center|width=280
|label=|position=right
|mark=Red circle.svg|mark_width=10|mark_link=α Sge
|x=460|y=280
}}
|caption=Location of α Sagittae (circled)
}}
{{Starbox observe
| epoch = J2000.0
| constell = Sagitta
}}
{{Starbox character
| type = bright giant
}}
{{Starbox astrometry
| radial_v = {{val|+1.72|0.16}}
| prop_mo_ra = {{val|+14.630|0.257}}
| prop_mo_dec = {{val|-20.160|0.276}}
| parallax =8.5307
| p_error = 0.1848
| parallax_footnote = {{cite DR2|1824277055360974720}}
}}
{{Starbox detail
}}
{{Starbox catalog
| names = {{odlist | name=Sham | name2=Alsahm | B=α Sge | F=5 Sagittae | BD=+17°4042 | FK5=1133 | HD=185758 | HIP=96757 | HR=7479 | SAO=105120 | GC=27215 | CCDM=J19401+1801A | IDS=19356+1747 A | PPM=136737 | WDS=J19401+1801A }}{{cite simbad | title=5 Sge | access-date=2019-03-30 }}
}}
{{Starbox reference
| Simbad = 5+Sagittae
}}
{{Starbox end}}
Alpha Sagittae, formally named Sham {{IPAc-en|'|sh|æ|m}},{{cite book
|last1=Kunitzsch |first1=Paul
|last2=Smart |first2=Tim
|date = 2006 |edition = 2nd rev.
|title = A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations
|publisher = Sky Pub |location = Cambridge, Massachusetts
|isbn = 978-1-931559-44-7
}} is a single star in the northern constellation of Sagitta. Alpha Sagittae is the Bayer designation, which is latinized from α Sagittae and abbreviated Alpha Sge or α Sge. It is visible to the naked eye as a yellow-hued star with an apparent visual magnitude of +4.38. Despite the name, this is not the brightest star in the constellation – that distinction belongs to Gamma Sagittae. Based upon parallax measurements, Alpha Sagittae is approximately 382 light-years from the Sun. It is moving further away from the Earth with a heliocentric radial velocity of 1.7 km/s.
This is an evolved bright giant with a stellar classification of G1 II. It is 151 million years old with 4 times the mass of the Sun and has expanded to around 21 times the Sun's radius. It is radiating 340 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 5,333 K. There is an X-ray source within {{Val|12|ul=arcsecond}} of these coordinates.
The evolutionary state of Alpha Sagittae is unclear. Its temperature and luminosity place it within the Hertzsprung gap, a region of the H-R diagram where stars more massive than the sun are evolving rapidly away from the main sequence towards becoming red giants. However, the chemical composition of its surface indicates that it has already experienced the first dredge-up of fusion products that occurs soon after a star reaches the red giant branch. It also lies within the Cepheid instability strip, but is not a Cepheid variable.{{cite journal |bibcode=1999PASP..111...84V |title=Carbon, Nitrogen, and Oxygen Abundances of Selected Stars in the Hertzsprung Gap |journal=Publications of the Astronomical Society of the Pacific |volume=111 |issue=755 |pages=84 |last1=Vanture |first1=Andrew D. |last2=Wallerstein |first2=George |year=1999 |doi=10.1086/316306 |doi-access=free }} It belongs to a small group of known stars that have been called carbon-deficient red giants and may have experienced binary mass exchanges.{{cite journal |bibcode=2019ApJ...887...12B |title=Carbon-deficient Red Giants |journal=The Astrophysical Journal |volume=887 |issue=1 |pages=12 |last1=Bond |first1=Howard E. |year=2019 |arxiv=1910.06256 |doi=10.3847/1538-4357/ab4e13 |s2cid=204512549 |doi-access=free }}
Nomenclature
This star bore the traditional name Sham (or Alsahm), which derives from the Arabic word سهم sahm, meaning "arrow", the name formerly having been applied to the whole constellation. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN approved the name Sham for this star on 12 September 2016 and it is now so included in the List of IAU-approved Star Names.
In Chinese, {{lang|zh|左旗}} ({{lang|zh-Latn|Zuǒ Qí}}), meaning Left Flag, refers to an asterism consisting of Alpha Sagittae, Beta Sagittae, Delta Sagittae, Zeta Sagittae, Gamma Sagittae, 13 Sagittae, 11 Sagittae, 14 Sagittae and Rho Aquilae. Consequently, the Chinese name for Alpha Sagittae itself is {{lang|zh|左旗一}} ({{lang|zh-Latn|Zuǒ Qí yī}}, {{langx|en|the First Star of Left Flag}}).{{in lang|zh}} [http://aeea.nmns.edu.tw/2006/0607/ap060703.html AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 3 日] {{Webarchive|url=https://web.archive.org/web/20110521232833/http://aeea.nmns.edu.tw/2006/0607/ap060703.html |date=2011-05-21 }}
References
{{reflist|refs=
| accessdate=22 May 2016 }}
{{cite journal | display-authors=1 | last1=van Belle | first1=G. T. | last2=Creech-Eakman | first2=M. J. | last3=Hart | first3=A. | title=Supergiant temperatures and linear radii from near-infrared interferometry | journal=Monthly Notices of the Royal Astronomical Society | date=2009 | volume=394 | issue=4 | pages=1925 | bibcode=2009MNRAS.394.1925V | arxiv=0811.4239 | doi=10.1111/j.1365-2966.2008.14146.x | doi-access=free | s2cid=118372600 }}
{{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 | doi-access=free | bibcode=2008MNRAS.389..869E | arxiv=0806.2878 | s2cid=14878976 }}
| journal=Astronomy & Astrophysics | arxiv=1408.5529 | volume=575 | id=A42 | pages=67 | date=March 2015 | doi=10.1051/0004-6361/201322844 | bibcode=2015A&A...575A..42G | s2cid=59501196 }}
}}
{{Stars of Sagitta}}
{{Authority control}}
{{DEFAULTSORT:Alpha Sagittae}}