Global InformationBeta1 Sagittarii information
 | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Sagittarius |
| Right ascension | 19h 22m 38.29770s[1] |
| Declination | −44° 27′ 32.2458″[1] |
| Apparent magnitude (V) | +4.01[2] |
| Characteristics | |
| Spectral type | B9 V + A5 V[3][4] |
| U−B color index | −0.39[2] |
| B−V color index | −0.10[2] |
| Astrometry | |
| Radial velocity (Rv) | −10.7±2.7[5] km/s |
| Proper motion (μ) | RA: +13.67[1] mas/yr Dec.: −19.03[1] mas/yr |
| Parallax (π) | 10.40 ± 1.14 mas[1] |
| Distance | approx. 310 ly (approx. 100 pc) |
| Absolute magnitude (MV) | −1.32[6] |
| Details | |
| β1 Sgr A | |
| Mass | 3.67±0.14[7] M☉ |
| Radius | 2.73[4] R☉ |
| Luminosity | 324[7] L☉ |
| Surface gravity (log g) | 3.83[8] cgs |
| Temperature | 11,960[8] K |
| Metallicity [Fe/H] | −0.35[8] dex |
| Rotational velocity (v sin i) | 85±13[4] km/s |
| Age | 224[9] Myr |
| β1 Sgr B | |
| Radius | 1.89[4] R☉ |
| Rotational velocity (v sin i) | 140±21[4] km/s |
| Other designations | |
Arkab Prior, β1 Sgr, CD−44° 13277, FK5 1502, HD 181454, HIP 95241, HR 7337, SAO 229646, WDS J19226-4428A[10] | |
| Database references | |
| SIMBAD | data |
Beta1 Sagittarii, Latinized from β1 Sagittarii, is a binary star system in the zodiac constellation of Sagittarius,[11] next to the southern constellation border with Telescopium. The brighter primary is named Arkab Prior /ˈɑːrkæb ˈpraɪər/, the traditional name of the system.[12][13] It is visible to the naked eye with a combined apparent visual magnitude of +4.01.[2] Based upon an annual parallax shift of 10.40 mas as seen from Earth,[1] it is located roughly 310 light-years from the Sun. At Beta1 Sagittarii's distance, the visual magnitude is diminished by an extinction factor of 0.17 due to interstellar dust.[9]
The pair of stars that constitute this system have an angular separation of 28.3[11] arc seconds, with an estimated physical separation of about 3,290 AU.[4] The primary, Beta1 Sagittarii A, is a B-type main sequence star with a stellar classification of B9 V.[3][4] It is about 95% of the way through its lifespan on the main sequence.[7] The star has around 3.7[7] times the mass of the Sun and 2.7[4] times the Sun's radius. It is an estimated 224[9] million years old and is spinning with a projected rotational velocity of 85 km/s.[4] The star is radiating 324[7] times the luminosity of the Sun from its photosphere at an effective temperature of 11,960 K.[8]
The companion, Beta1 Sagittarii B, is a magnitude 7.4[11] A-type main sequence star with a class of A5 V.[3] It has 1.89[4] times the radius of the Sun and may be spinning faster than the primary with a projected rotational velocity of 140 km/s.[4]
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