15 Sagittarii
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Sagittarius |
| Right ascension | 18h 15m 12.90641s |
| Declination | −20° 43′ 41.7738″ |
| Apparent magnitude (V) | 5.37 |
| Characteristics | |
| Spectral type | O9.7 Iab or B0 Iab |
| B−V color index | 0.007±0.004 |
| Astrometry | |
| Radial velocity (Rv) | −6.3±2.8 km/s |
| Proper motion (μ) | RA: +1.60 mas/yr Dec.: −1.51 mas/yr |
| Parallax (π) | 0.10±0.45 mas |
| Distance | 4,200±650 ly (1,300±200 pc) |
| Details | |
| 15 Sgr Aa | |
| Mass | ~30 M☉ |
| Radius | 28.6±12.5 R☉ |
| Luminosity | 4.47+3.85 −2.07×105 L☉ |
| Surface gravity (log g) | 3.10 cgs |
| Temperature | 28,000±1,000 K |
| Rotational velocity (v sin i) | 83±7 km/s |
| Other designations | |
| 15 Sgr, BD−20° 5054, HD 167264, HIP 89439, HR 6822, SAO 186543, WDS J18152-2044 | |
| Database references | |
| SIMBAD | data |
15 Sagittarii is a blue-hued binary star system in the southern zodiac constellation of Sagittarius. The estimated distance based upon photometry is around 4,200 ly (1,300 pc). It is faintly visible to the naked eye with an apparent visual magnitude of 5.37. The system is moving closer to the Sun with a heliocentric radial velocity of around −6 km/s.
Chini et al. (2012) identify this as a double-lined spectroscopic binary star system. It shows a stellar classification of O9.7 Iab, matching a massive O-type supergiant star. Along with the O-type star 16 Sgr (HD 167263), it is ionizing an H II region along the western edge of the molecular cloud L291.
The Washington Double Star Catalog lists four companions within a 2 arcsecond angular radius.