Zeta Sagittarii
star system in the constellation Sagittarius
Zeta Sagittarii (ζ Sagittarii, abbreviated Zeta Sgr, ζ Sgr) is a triple star system and the third-brightest star in the constellation of Sagittarius after Kaus Australis and Nunki. Based upon parallax measurements, it is about 88 light-years (27 parsecs) from the Sun.
The three components are designated Zeta Sagittarii Aa (officially named Ascella , the traditional name for the entire system), Ab and B. The Washington Double Star Catalog cites a component separated 72.3" from the system, but it is a background star unrelated to the pair.
Nomenclature
ζ Sagittarii (Latinised to Zeta Sagittarii) is the system's Bayer designation. The designations of the three components as ζ Sagittarii Aa, Ab and B derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).
It bore the traditional name Ascella, from a Late Latin word meaning armpit. In the catalogue of stars in the Calendarium of Al Achsasi al Mouakket, this star was designated Thalath al Sadirah, which was translated into Latin as Tertia τού al Sadirah, meaning third returning ostrich. In 2016, the IAU organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems. It approved the name Ascella for the component Zeta Sagittarii A on 12 September 2016 and it is now so included in the List of IAU-approved Star Names.
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This entry incorporates text from “Zeta Sagittarii” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.