Zeta Sagittae
 Location of ζ Sagittae (circled) |
|
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) |
|
|---|---|
| Constellation | Sagitta |
| Right ascension | 19h 48m 58.65978s |
| Declination | +19° 08′ 31.3516″ |
| Apparent magnitude (V) | +5.00(5.64 + 6.04 + 9.01) |
| Characteristics | |
| Spectral type | A3 Vnn(A1 V + A3 V) |
| U−B color index | +0.06 |
| B−V color index | +0.10 |
| Astrometry | |
| Proper motion (μ) |
RA: +17.63 mas/yr Dec.: +26.27 mas/yr |
| Parallax (π) | 12.79 ± 0.67mas |
| Distance | 260 ± 10 ly (78 ± 4 pc) |
| Orbit | |
| Period (P) | 8487.9±4.9 d |
| Semi-major axis (a) | 0.13605±0.00044″ |
| Eccentricity (e) | 0.7948±0.0019 |
| Inclination (i) | 132.33±0.41° |
| Longitude of the node (Ω) | 340.97±0.68° |
| Periastron epoch (T) | 44199.6 ± 5.9 HMJD |
|
Argument of periastron (ω) (secondary) |
355.3±1.0° |
| Details | |
| ζ Sge A | |
| Mass | 1.80 M☉ |
| Radius | 1.7 R☉ |
| Luminosity | 46 L☉ |
| Surface gravity (log g) | 3.89 cgs |
| Temperature | 8,422±286 K |
| Rotational velocity (v sin i) | 240 km/s |
| Age | 347 Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
Zeta Sagittae (ζ Sagittae) is triple star system in the northern constellation of Sagitta. It is visible to the naked eye, having a combined apparent visual magnitude of +5.00. Based upon an annual parallax shift of 12.79 mas, the distance to this star is approximately 260 light years.
The inner pair is a visual binary system consisting of two A-type main-sequence stars with an orbital period of 23.2 years (8,487.9 d), a semimajor axis of 0.136 arc seconds, and an eccentricity of 0.79. The primary, component A, has a visual magnitude of 5.64 with a stellar classification of A3 Vnn, where the 'nn' suffix indicates "nebulous" lines due to rotation. It is spinning rapidly with a projected rotational velocity of 240 km/s. This is giving the star an oblate shape with an equatorial bulge that is 14% larger than the polar radius.
The secondary member, component B, is a magnitude 6.04 star, while the more distant component C is magnitude 9.01 and lies at an angular separation of 8.330 arc seconds from the other two.
In Chinese, 左旗 (Zuǒ Qí), meaning Left Flag, refers to an asterism consisting of ζ Sagittae, α Sagittae, β Sagittae, δ Sagittae, γ Sagittae, 13 Sagittae, 11 Sagittae, 14 Sagittae and ρ Aquilae. Consequently, ζ Sagittae itself is known as 左旗四 (Zuǒ Qí sì, English: the Fourth Star of Left Flag.)
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