The three components are designated Pi Sagittarii A (also named Albaldah[1]), B and C.[17]
Nomenclature
π Sagittarii (Latinised to Pi Sagittarii) is the system's Bayer designation. The designations of the three constituents as Pi Sagittarii A, B and C, derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).[2]The system bore the traditional name Albaldah[23], which comes from the Arabic بلدة bálda 'the town'.[24] In 2016, the IAU organized a Working Group on Star Names (WGSN)[3] to catalog and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems.[4] It approved the name Albaldah for the component Pi Sagittarii A on 5 September 2017 and it is now so included in the List of IAU-approved Star Names.[1]
In the catalogue of stars in the Calendarium of Al Achsasi al Mouakket, this star was designated Nir al Beldat, which was translated into Latin as Lucida Oppidi, meaning 'the brightest of the town'.[28]
This system, together with Zeta Sagittarii and Sigma Sagittarii may have been the Akkadian Gu-shi-rab‑ba, 'the Yoke of the Sea'.[5]
In Chinese, {{lang|zh|建}} ({{lang|zh-Latn|Jiàn}}), meaning Establishment, refers to an asterism consisting of Pi Sagittarii, Xi² Sagittarii, Omicron Sagittarii, 43 Sagittarii, Ro¹ Sagittarii and Upsilon Sagittarii. Consequently, Pi Sagittarii itself is known as {{lang|zh|建三}} ({{lang|zh-Latn|Jiàn sān}}, {{lang-en|the Third Star of Establishment}}.)[6]
Properties
The spectrum of the system's primary, Pi Sagitarii A, matches a stellar classification of F2 II.[3] The 'II' luminosity class is for a bright giant star that has exhausted the hydrogen at its core and has followed an evolutionary track away from the main sequence of stars like the Sun. Because it has nearly six times the mass of the Sun,[3] it reached this stage in a mere 67 million years.[3] The outer envelope is radiating energy at an effective temperature of about 6,590 K,[3] giving it the yellow-white hue of an F-type star.[35]
Pi Sagittarii A has two nearby companions. The first is located at an angular separation of 0.1 arcseconds or at least 13 AUs. The second is 0.4 arcseconds away, which is 40 AU or more. Nothing is known about the orbits of these stars.[24]
Because it is close to the ecliptic, Pi Sagittarii can sometimes be occulted by the Moon, and, very rarely, planets of the Solar System. The next occultation by a planet takes place on February 17, 2035, when it will be occulted by Venus.[37]
References
1. ^1 {{cite web | url=https://www.iau.org/public/themes/naming_stars/ | title=Naming Stars |publisher=IAU.org |accessdate=16 December 2017}}
2. ^{{cite arXiv |title=On the naming convention used for multiple star systems and extrasolar planets |date=2010 |eprint=1012.0707 |class=astro-ph.SR |last1= Hessman |first1=F. V. |last2= Dhillon |first2=V. S. |last3= Winget |first3=D. E. |last4= Schreiber |first4=M. R. |last5= Horne |first5=K. |last6= Marsh |first6=T. R. |last7= Guenther |first7=E. |last8= Schwope |first8=A. |last9= Heber |first9=U. }}
3. ^{{cite web | url=https://www.iau.org/science/scientific_bodies/working_groups/280/ | title=IAU Working Group on Star Names (WGSN)|accessdate=22 May 2016}}
4. ^{{cite web | url=https://www.iau.org/static/science/scientific_bodies/working_groups/280/wg-starnames-triennial-report-2015-2018.pdf | page=5 | title=WG Triennial Report (2015-2018) - Star Names |accessdate=2018-07-14}}
5. ^1 {{cite book | last=Allen | first=R. H. | year=1963 | authorlink=Richard Hinckley Allen | title=Star Names: Their Lore and Meaning | url=http://penelope.uchicago.edu/Thayer/E/Gazetteer/Topics/astronomy/_Texts/secondary/ALLSTA/Sagittarius*.html | accessdate=2012-09-04 | edition=Reprint | publisher=Dover Publications Inc | location=New York | isbn=0-486-21079-0 | page=355}}
6. ^{{zh icon}} AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 5 月 11 日
7. ^1 {{citation | 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 | postscript=. }}
8. ^1 2 3 4 5 6 7 8 9 10 11 {{citation | display-authors=1 | last1=Lyubimkov | first1=Leonid S. | last2=Lambert | first2=David L. | last3=Rostopchin | first3=Sergey I. | last4=Rachkovskaya | first4=Tamara M. | last5=Poklad | first5=Dmitry B. | title=Accurate fundamental parameters for A-, F- and G-type Supergiants in the solar neighbourhood | journal=Monthly Notices of the Royal Astronomical Society | volume=402 | issue=2 | pages=1369–1379 |date=February 2010 | doi=10.1111/j.1365-2966.2009.15979.x | bibcode=2010MNRAS.402.1369L |arxiv = 0911.1335 }}
9. ^1 {{citation | last=Wilson | first=R. E. | year=1953 | title=General Catalogue of Stellar Radial Velocities | publisher=Carnegie Institute of Washington, D.C. | bibcode=1953GCRV..C......0W }}
10. ^1 {{citation | last1=Bernacca | first1=P. L. | last2=Perinotto | first2=M. | title=A Catalogue of Stellar Rotational Velocities | journal=Contributi Osservatorio Astronomico di Padova in Asiago | volume=239 | issue=1 | year=1970 | bibcode=1970CoAsi.239....1B }}
11. ^1 2 {{citation | last1=Nicolet | first1=B. | year=1978 | title=Photoelectric photometric Catalogue of homogeneous measurements in the UBV System | journal=Astronomy and Astrophysics Supplement Series | volume=34 | pages=1–49 | bibcode=1978A&AS...34....1N }}
12. ^1 2 {{citation | title=CCDM J19098-2101AB -- Double or multiple star | work=SIMBAD | publisher=Centre de Données astronomiques de Strasbourg | url=http://simbad.u-strasbg.fr/simbad/sim-id?Ident=Pi+Sagittarii | accessdate=2012-01-15 }}
13. ^1 2 {{citation | first1=James B. | last1=Kaler | title=ALBALDAH (Pi Sagitarii) | work=Stars | publisher=University of Illinois | url=http://stars.astro.illinois.edu/sow/albaldah.html | accessdate=2012-01-21 }}
14. ^1 {{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 | pages=429–438 |date=June 1895 | bibcode=1895MNRAS..55..429K | doi=10.1093/mnras/55.8.429}}
15. ^1 {{citation | title=The Colour of Stars | date=December 21, 2004 | work=Australia Telescope, Outreach and Education | publisher=Commonwealth Scientific and Industrial Research Organisation | url=http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html | accessdate=2012-01-16 }}
16. ^1 {{citation | first1=Peter | last1=Grego | chapter=7. Observing Venus | title=Venus and Mercury, and How to Observe Them | series=Astronomers' Observing Guides | year=2008 | pages=229–247 | doi=10.1007/978-0-387-74286-1_7 }}