Phi Sagittarii
 Location of φ Sagittarii (circled) |
|
| Observation data Epoch J2000 Equinox J2000 |
|
|---|---|
| Constellation | Sagittarius |
| Right ascension | 18h 45m 39.38610s |
| Declination | –26° 59′ 26.7944″ |
| Apparent magnitude (V) | 3.17 |
| Characteristics | |
| Spectral type | B8.5 III to B7 IV |
| U−B color index | –0.36 |
| B−V color index | –0.11 |
| Astrometry | |
| Radial velocity (Rv) | +21.5 km/s |
| Proper motion (μ) |
RA: +50.61 mas/yr Dec.: +1.22 mas/yr |
| Parallax (π) | 13.63 ± 0.19mas |
| Distance | 239 ± 3 ly (73 ± 1 pc) |
| Details | |
| Mass | 4–4.2 M☉ |
| Radius | 4.8 R☉ |
| Luminosity | 475 L☉ |
| Temperature | 14,990 K |
| Rotational velocity (v sin i) | 35 km/s |
| Age | 1.65 × 108 years |
| Other designations | |
| Database references | |
| SIMBAD | data |
Phi Sagittarii (Phi Sgr, φ Sagittarii, φ Sgr) is a star in the southern constellation of Sagittarius. With an apparent visual magnitude of 3.17, it is the ninth-brightest star in the constellation and is readily visible to the naked eye. Parallax measurements place it at a distance of roughly 239 light-years (73 parsecs) from the Earth.
The stellar classification of this star has been rated at B8.5 III and B7 IV, with a luminosity class of III indicating it is a giant star, while a class of IV suggests it is still a subgiant star. Both represent stages in the evolution of a star after it has exhausted the hydrogen at its core. This energy is being radiated from the star's outer envelope at an effective temperature of 14,990 K, which produces the blue-white hue typical of B-type stars.
In the past, this star catalogued as a spectroscopic binary and a companion was apparently detected through lunar occultation. However, it is most likely a solitary star and any nearby stars are merely optical companions.
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