Psi Sagittarii
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Sagittarius |
| Right ascension | 19h 15m 32.42658s |
| Declination | −25° 15′ 24.0569″ |
| Apparent magnitude (V) | +4.86 |
| Characteristics | |
| Spectral type | K2 III + A9 III + A3 V |
| B−V color index | 0.569±0.006 |
| Astrometry | |
| Radial velocity (Rv) | −11.43±1.47 km/s |
| Proper motion (μ) | RA: +45.50 mas/yr Dec.: −31.08 mas/yr |
| Parallax (π) | 10.93±0.31 mas |
| Distance | 298 ± 8 ly (91 ± 3 pc) |
| Absolute magnitude (MV) | 0.06 |
| Orbit | |
| Period (P) | 7,319 d |
| Eccentricity (e) | 0.51 |
| Periastron epoch (T) | 2442418.795 JD |
| Argument of periastron (ω) (secondary) | 2.6° |
| Semi-amplitude (K1) (primary) | 10.0 km/s |
| Semi-amplitude (K2) (secondary) | 13.8 km/s |
| Details | |
| A | |
| Mass | 2.10 M☉ |
| Luminosity | 84 L☉ |
| Ba/Bb | |
| Mass | 1.70/2.70 M☉ |
| Other designations | |
| ψ Sgr, 42 Sgr, CPD−27°6737, HD 179950, HIP 94643, HR 7292, SAO 187882, WDS J19155-2515 | |
| Database references | |
| SIMBAD | data |
Psi Sagittarii, which is Latinized from ψ Sagittarii, is a triple star system in the zodiac constellation of Sagittarius. The star system is located at a distance of 298 light years from the Earth based on parallax, but is drifting closer with a heliocentric radial velocity of −12 km/s. The system is faintly visible to the naked eye has a combined apparent visual magnitude of +4.86.
The inner pair of this triple star system, components Ba and Bb, have an orbital period of 10.78 days and an eccentricity of 0.47. The pair consist of an A-type giant and a less evolved A-type main-sequence star with stellar classifications of A9 III + A3 V, respectively. These in turn share an orbit with the primary, component A, having a period of 20 years and an eccentricity of 0.51. The last is an orange-hued K-type giant with a class of K2 III.