Theta Sagittae
Theta Sagittae (θ Sagittae) is a double star in the northern constellation of Sagitta. With a combined apparent visual magnitude of +6, it is near the limit of stars that can be seen with the naked eye. According to the Bortle scale the star is visible in dark suburban/rural skies. Based upon an annual parallax shift of 22.15 mas as seen from Earth, it is located roughly 147 light years from the Sun.
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Sagitta |
| A | |
| Right ascension | 20h 09m 56.6470s |
| Declination | +20° 54′ 54.094″ |
| Apparent magnitude (V) | +6.516 |
| B | |
| Right ascension | 20h 09m 56.2405s |
| Declination | +20° 55′ 04.228″ |
| Apparent magnitude (V) | +8.769 |
| Characteristics | |
| A | |
| Spectral type | F3V |
| U−B color index | −0.04 |
| B−V color index | +0.38 |
| B | |
| Spectral type | G5V |
| B−V color index | +0.732 |
| Astrometry | |
| A | |
| Radial velocity (Rv) | −40.92 km/s |
| Proper motion (μ) | RA: +58.387 mas/yr Dec.: +98.274 mas/yr |
| Parallax (π) | 22.3262 ± 0.0326 mas |
| Distance | 146.1 ± 0.2 ly (44.79 ± 0.07 pc) |
| Absolute magnitude (MV) | +3.24 |
| B | |
| Radial velocity (Rv) | −43.0 km/s |
| Proper motion (μ) | RA: +64.726 mas/yr Dec.: +101.800 mas/yr |
| Parallax (π) | 22.3841 ± 0.0305 mas |
| Distance | 145.7 ± 0.2 ly (44.67 ± 0.06 pc) |
| Absolute magnitude (MV) | +5.58 |
| Details | |
| A | |
| Mass | 1.52 M☉ |
| Radius | 1.45 R☉ |
| Luminosity | 4.0 L☉ |
| Surface gravity (log g) | 4.32 cgs |
| Temperature | 6,750±229 K |
| Metallicity [Fe/H] | −0.17 dex |
| Rotational velocity (v sin i) | 33.6 km/s |
| Age | 2.089 Gyr |
| B | |
| Mass | 0.95 M☉ |
| Radius | 0.82 R☉ |
| Luminosity | 0.516 L☉ |
| Surface gravity (log g) | 4.526 cgs |
| Temperature | 5,394 K |
| Other designations | |
| A: HIP 99352, HR 7705, SAO 88276 | |
| B: HIP 99351, SAO 88275 | |
| Database references | |
| SIMBAD | A |
| B | |
The binary pair consists of two stars separated by 502 AU. The primary, component A, is an F-type main sequence star with a stellar classification of F3V. This star is about two billion years old with 52% more mass than the Sun. It forms a double star with a magnitude 8.85 companion, which is located at an angular separation of 11.58 arc seconds along a position angle of 331.1°, as of 2011. The star is sometimes described as a triple star, with a 7th magnitude companion 91″ away. This is an unrelated giant star much further away than the close pair. A fainter star separated by nearly 3′ was also listed as a companion by Struve, again just an accidental optical association.