Delta Sagittae
 Location of δ Sagittae (circled) |
|
| Observation data Epoch J2000 Equinox J2000 |
|
|---|---|
| Constellation | Sagitta |
| Right ascension | 19h 47m 23.26253s |
| Declination | +18° 32′ 03.4401″ |
| Apparent magnitude (V) | +3.82 (3.91 / 6.64) |
| Characteristics | |
| Spectral type | M2II + B9.5V |
| U−B color index | +0.98 |
| B−V color index | +1.40 |
| Astrometry | |
| Radial velocity (Rv) | 2.5 ± 0.9 km/s |
| Proper motion (μ) |
RA: -4.31 mas/yr Dec.: 12.35 mas/yr |
| Parallax (π) | 5.49 ± 0.72mas |
| Distance | approx. 590 ly (approx. 180 pc) |
| Orbit | |
| Period (P) | 10.11 yr |
| Semi-major axis (a) | 0.051″ |
| Eccentricity (e) | 0.44 |
| Inclination (i) | 140.0° |
| Longitude of the node (Ω) | 170.2° |
| Periastron epoch (T) | 1979.93 |
|
Argument of periastron (ω) (secondary) |
257.7° |
| Details | |
| δ Sge A | |
| Mass |
3.35+0.335 −0.30 M☉ |
| Radius |
129+13 −12 R☉ |
| Luminosity | 2500 L☉ |
| Surface gravity (log g) | 0.74 ± 0.10 cgs |
| Temperature |
3600+288 −267 K |
| δ Sge B | |
| Mass | 2.9 M☉ |
| Radius | 2.6 R☉ |
| Luminosity | 63 L☉ |
| Temperature | 10000 K |
| Other designations | |
| Database references | |
| SIMBAD | data |
Delta Sagittae (Delta Sge, δ Sagittae, δ Sge) is a binary star in the constellation of Sagitta, with an apparent magnitude of +3.68. The primary component is a red M-type bright giant, and the secondary is a B-type main-sequence star. It is approximately 590 light years from Earth, based on its parallax.
Delta Sagittae is a spectroscopic binary with a composite spectrum, meaning that light from both stars can be detected. It has an orbital period of about 10 years and an eccentricity of about 0.44.
Delta Sagittae is moving through the Galaxy at a speed of 9.8 km/s relative to the Sun. Its projected Galactic orbit carries it between 23,800 and 35,300 light years from the center of the Galaxy.
In Chinese, 左旗 (Zuǒ Qí), meaning Left Flag, refers to an asterism consisting of δ Sagittae, α Sagittae, β Sagittae, ζ Sagittae, γ Sagittae, 13 Sagittae, 11 Sagittae, 14 Sagittae and ρ Aquilae. Consequently, δ Sagittae itself is known as 左旗三 (Zuǒ Qí sān, English: the Third Star of Left Flag.)
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