Beta Sagittae
Star in the constellation Sagitta
From Wikipedia, the free encyclopedia
Beta Sagittae, Latinized from β Sagittae, is a single[11] star in the northern constellation of Sagitta. It is a faint star but visible to the naked eye with an apparent visual magnitude of 4.38.[2] Based upon an annual parallax shift of 7.7237 mas as seen from the Gaia satellite, it is located 420 light years from the Sun. The star is moving closer to the Sun with a radial velocity of −22 km/s.[5]
 | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Sagitta |
| Right ascension | 19h 41m 02.93907s[1] |
| Declination | +17° 28′ 33.7528″[1] |
| Apparent magnitude (V) | 4.38[2] |
| Characteristics | |
| Spectral type | G8 IIIa CN 0.5[3] |
| U−B color index | +0.89[4] |
| B−V color index | +1.05[4] |
| R−I color index | +0.50[4] |
| Astrometry | |
| Radial velocity (Rv) | −22.0±0.3[5] km/s |
| Proper motion (μ) | RA: 7.682 ± 0.258[6] mas/yr Dec.: −32.987 ± 0.279[6] mas/yr |
| Parallax (π) | 7.7237±0.1941 mas[6] |
| Distance | 420 ± 10 ly (129 ± 3 pc) |
| Absolute magnitude (MV) | −1.39+0.22 −0.20[7] |
| Details[8] | |
| Mass | 3.755±0.050 M☉ |
| Radius | 25.7±0.4 R☉ |
| Luminosity | 369±11 L☉ |
| Surface gravity (log g) | 2.20±0.02 cgs |
| Temperature | 4,990±20 K |
| Metallicity [Fe/H] | +0.00±0.03 dex |
| Rotational velocity (v sin i) | 9.1±0.7[7] km/s |
| Age | 129[9] Myr |
| Other designations | |
| β Sge, 6 Sagittae, BD+17°4048, FK5 1513, GC 27236, HD 185958, HIP 96837, HR 7488, SAO 105133, PPM 136766[10] | |
| Database references | |
| SIMBAD | data |
This is an evolved red giant[9] with a stellar classification of G8 IIIa CN 0.5.[3] The suffix notation indicates a mild overabundance of the cyanogen molecule in the spectrum. Beta Sagittae is an estimated 129 million years old[12] with 3.755 times the mass of the Sun, and has expanded to 25.7 times the Sun's radius. The star is radiating 369 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,990 K.[8]
Naming
In Chinese, 左旗 (Zuǒ Qí), meaning Left Flag, refers to an asterism consisting of β Sagittae, α Sagittae, δ Sagittae, ζ Sagittae, γ Sagittae, 13 Sagittae, 11 Sagittae, 14 Sagittae and ρ Aquilae. Consequently, the Chinese name for β Sagittae itself is 左旗二 (Zuǒ Qí èr, English: the Second Star of Left Flag.)[13]