| Observation data Epoch J2000.0 Equinox J2000.0 |
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|---|---|
| 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 | |
The Bayer designation Beta Sagittarii (β Sgr, β Sagittarii) is shared by two star systems, β¹ Sagittarii and β² Sagittarii, in the constellation Sagittarius. The two stars are separated by 0.36° in the sky. Beta Sagittarii also has the traditional name Arkab, from the Arabic عرقوب carqūb meaning hamstring.
Beta-1 Sagittarii, also called Arkab Prior since it leads β² across the sky, is a binary star lying 378 light years from Earth. Arkab Prior A is a spectral type B9 main sequence dwarf which has an apparent magnitude of +3.96. Arkab Prior B is a type A3 dwarf with an apparent magnitude of +7.4. The two stars are separated in the sky by 28 arcseconds, which puts them at least 3300 astronomical units apart.
| Observation data Epoch J2000.0 Equinox J2000.0 |
|
|---|---|
| Constellation | Sagittarius |
| Right ascension | 19h 23m 13.2s |
| Declination | -44° 47' 59" |
| Apparent magnitude (V) | +4.27 |
| Distance | 139 ± 5 ly (43 ± 2 pc) |
| Spectral type | F2III |
| Other designations | |
Beta-2 Sagittarii, also called Arkab Posterior since it trails β¹ across the sky, is a spectral type F2 giant which has an apparent magnitude of +4.27. It is 137 light years from Earth.
USS Arkab (AK-130) was a United States Navy Crater class cargo ship named after the star.
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