Delta Sagittae
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 430 light years from Earth, based on its Gaia Data Release 2 parallax.
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Sagitta |
| Right ascension | 19h 47m 23.26653s |
| Declination | +18° 32′ 03.5203″ |
| 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 |
| Variable type | LB? |
| Astrometry | |
| Radial velocity (Rv) | 2.5 ± 0.9 km/s |
| Proper motion (μ) | RA: -6.514 mas/yr Dec.: 0.849 mas/yr |
| Parallax (π) | 5.9674 ± 0.2597 mas |
| Distance | 550 ± 20 ly (168 ± 7 pc) |
| Absolute magnitude (MV) | −2.58 |
| 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 | 108 R☉ |
| Luminosity | 1,888 - 1,923 L☉ |
| Surface gravity (log g) | 0.74 ± 0.10 cgs |
| Temperature | 3,660±170 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 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. It is also a variable star, with its brightness changing between a maximum of magnitude 3.75 and a minimum of 3.83 in an unpredictable way.
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.