Beta2 Sagittarii
Beta2 Sagittarii is a star in the southern zodiac constellation of Sagittarius. It is visible to the naked eye, having an apparent visual magnitude of +4.29. Based upon an annual parallax shift of 24.31 mas as seen from Earth, it is located 134 light-years from the Sun.
Based upon variations in its proper motion, this is a probable astrometric binary system. As such, its two components would be designated Beta2 Sagittarii A and B.
Nomenclature
β2 Sagittarii is the system's Bayer designation. The designations of the two components as Beta2 Sagittarii A and B derive from the convention used by the Washington Multiplicity Catalog for multiple star systems, and adopted by the International Astronomical Union.In 2016, the International Astronomical Union organized a Working Group on Star Names to catalog and standardize proper names for stars. The WGSN approved the name Arkab Posterior for Beta2 Sagittarii on 5 October 2016 and it is now so included in the List of IAU-approved Star Names. For such names relating to members of multiple star systems, and where a component letter is not explicitly listed, the WGSN says that the name should be understood to be attributed to the brightest component by visual brightness.
In Chinese, 天淵, meaning Celestial Spring, refers to an asterism consisting of Beta2 Sagittarii, Beta1 Sagittarii and Alpha Sagittarii. Consequently, the Chinese name for Beta2 Sagittarii itself is 天淵一