Beta Sagittarii

β¹ Sagittarii

Location of Beta Sagittarii (circled)
Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Sagittarius
Right ascension	19h 22m 38.3s
Declination	−44° 27' 32"
Apparent magnitude (V)	+3.96
Distance	378 ± 42 ly (116 ± 13 pc)
Spectral type	B9V
Other designations
Arkab Prior, CCDM J19226-4428A, CPD-40  8955, FK5 1502, GC 26703, HD 181454, HIP 95241, HR 7337, PPM 325041 , SAO 229646, WDS J19226-4428A

Beta Sagittarii (β Sagittarii, abbreviated Beta Sgr, β Sgr) is the common designation shared by two star systems in the constellation of Sagittarius, themselves designated β¹ Sagittarii (itself a binary star) and β² Sagittarii. β¹ and β² Sagittarii are approximately 378 and 139 light years, respectively, from Earth. The two systems are separated by 0.36° in the sky.

β¹ Sagittarii's two components are designated β¹ Sagittarii A, also named Arkab Prior, and β¹ Sagittarii B (sometimes designated Arkab Prior A and B). β² Sagittarii is named Arkab Posterior. Beta Sagittarii is also referred to by the traditional name Arkab.

β Sagittarii (Latinised to Beta Sagittariii) is the system's Bayer designation; β¹ and β² Sagittarii, those of its two constituents. The designations of β¹'s components - β¹ Sagittarii A 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).

The system's traditional name Arkab derives from the Arabic عرقوب ^carqūb meaning Achilles Tendon. The two constituents bore the traditional names Arkab Prior and Arkab Posterior since β¹ leads β² (or β² follows β¹) across the sky. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN states that in the case of multiple stars the name should be understood to be attributed to the brightest component by visual brightness. The WGSN approved the names Arkab Prior and Arkab Posterior for β¹ Sagittarii A and β² Sagittarii on 5 October 2016 and they are now so entered in the IAU Catalog of Star Names.