Phi Sagittarii
{{short description|Binary star in the constellation Sagittarius}}
{{Starbox begin}}
{{Starbox image
| image =
{{Location mark
| image=Sagittarius IAU.svg
| float=center | width=250 | position=right
| mark=Red circle.svg | mark_width=10 | mark_link=φ Sgr
| x%=56.1 | y%=43.0
}}
| caption=Location of φ Sagittarii (circled)
}}
{{Starbox observe
| epoch = J2000
| dec = {{DEC|-26|59|26.7944}}
| constell = Sagittarius
}}
{{Starbox character
| variable =
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{{Starbox astrometry
| parallax = 13.63
| p_error = 0.19
}}
{{Starbox detail
| component1 = A
| metal_fe =
| component2 = B
}}
{{Starbox catalog
| names = {{odlist | name=Namalsadirah 1 | name2=Awal al Sadira | B=φ Sgr, Phi Sgr | F=27 Sagittarii | CPD=-27 5241 | FK5=1487 | GC=25661 | HD=173300 | HIP=92041 | HR=7039 | PPM=297231 | SAO=268859 }}
}}
{{Starbox reference|Simbad=phi+Sgr}}
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Phi Sagittarii, Latinized from φ Sagittarii, is a binary star in the southern constellation of Sagittarius. With an apparent visual magnitude of 3.17, it is the ninth-brightest star in the constellation and is readily visible to the naked eye. Parallax measurements place it at a distance of roughly {{Convert|239|ly|pc|abbr=off|lk=on}} from the Earth. It is receding with a radial velocity of +21.5 km/s.
The stellar classification of this star has been rated at B8.5 III, with the luminosity class of III indicating it is a giant star evolved away from the main sequence after it has exhausted the hydrogen at its core. This energy is being radiated from the star's outer envelope at an effective temperature of {{val|12487|u=K}}, which produces the blue-white hue typical of B-type stars.
This star has been catalogued as a spectroscopic binary{{Cite journal |last=Lee |first=O. J. |date=1910-11-01 |title=Measures on nineteen new spectroscopic binaries. |bibcode=1910ApJ....32..300L |journal=The Astrophysical Journal |volume=32 |pages=300–308 |doi=10.1086/141806 |issn=0004-637X|doi-access=free }} and a companion was apparently detected through lunar occultation. However, the latter was pointed out as spurious. Interferometric observations taken in 2017 finally revealed that Phi Sgr is indeed a binary. The companion is a main sequence star around 60% more massive than the Sun, with an orbital period of roughly a year and an orbital separation of {{val|1.31|ul=AU}}.
Name and etymology
In the catalogue of stars in the Calendarium of Al Achsasi al Mouakket, this star was designated Aoul al Sadirah, which was translated into Latin as Prima τού al Sadirah, meaning first returning ostrich.
In Chinese, {{lang|zh|斗}} ({{lang|zh-Latn|Dǒu}}), meaning Dipper, refers to an asterism consisting of φ Sagittarii, λ Sagittarii, μ Sagittarii, σ Sagittarii, τ Sagittarii and ζ Sagittarii. Consequently, the Chinese name for φ Sagittarii itself is {{lang|zh|斗宿一}} ({{lang|zh-Latn|Dǒu Xiù yī}}, {{langx|en|the First Star of Dipper}}.){{in lang|zh}} [http://aeea.nmns.edu.tw/2006/0605/ap060511.html AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 5 月 11 日] {{Webarchive|url=https://web.archive.org/web/20110522111637/http://aeea.nmns.edu.tw/2006/0605/ap060511.html |date=2011-05-22 }}
This star, together with γ Sgr, δ Sgr, ε Sgr, ζ Sgr, λ Sgr, σ Sgr and τ Sgr comprising the Teapot asterism. φ Sgr, σ Sgr, ζ Sgr, χ Sgr and τ Sgr were Al Naʽām al Ṣādirah (النعم السادرة), the Returning Ostriches. According to the catalogue of stars in the Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars, Al Naʽām al Ṣādirah or Namalsadirah was originally the title for four stars: φ Sgr as Namalsadirah I, τ Sgr as Namalsadirah II, χ1 Sgr as Namalsadirah III and χ2 Sgr as Namalsadirah IV (except σ Sgr and ζ Sgr) .
References
{{Reflist|30em|refs=
| title=XHIP: An extended hipparcos compilation
| last1=Anderson | first1=E. | last2=Francis | first2=Ch.
| journal=Astronomy Letters
| volume=38 | issue=5 | pages=331 | year=2012
| bibcode=2012AstL...38..331A | doi=10.1134/S1063773712050015
| arxiv=1108.4971 | s2cid=119257644 | postscript=. }}
| 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 | page=430 |date=June 1895
| issue=8
| bibcode=1895MNRAS..55..429K | doi=10.1093/mnras/55.8.429
| postscript=. | doi-access=free}}
| title = Teapot
| publisher = constellation-guide.com
| url = http://www.constellation-guide.com/teapot/
| access-date = 2017-05-13 | postscript=. }}
| url=https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19720005197_1972005197.pdf
| first1=Jack W. | last1=Rhoads
| title=Technical Memorandum 33-507-A Reduced Star Catalog Containing 537 Named Stars
| location=Jet Propulsion Laboratory, California Institute of Technology
| date=November 15, 1971 | postscript=. }}
{{citation | 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 }}
| last1=David | first1=Trevor J. | last2=Hillenbrand | first2=Lynne A.
| title=The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets
| journal=The Astrophysical Journal | postscript=.
| volume=804 | issue=2 | pages=146 | year=2015
| bibcode=2015ApJ...804..146D | arxiv=1501.03154
| doi=10.1088/0004-637X/804/2/146 | s2cid=33401607 }}
}}
{{Stars of Sagittarius}}
{{DEFAULTSORT:Phi Sagittarii}}
Category:Sagittarius (constellation)