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Theta2 Sagittarii
  | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Sagittarius |
| Right ascension | 19h 59m 51.35684s[1] |
| Declination | −34° 41′ 52.0797″[1] |
| Apparent magnitude (V) | +5.30[2] |
| Characteristics | |
| Spectral type | A4/A5 IV[3] |
| U−B color index | +0.06[2] |
| B−V color index | +0.17[2] |
| Astrometry | |
| Radial velocity (Rv) | −17.60[4] km/s |
| Proper motion (μ) | RA: +108.23[1] mas/yr Dec.: −69.51[1] mas/yr |
| Parallax (π) | 20.62 ± 0.28 mas[1] |
| Distance | 158 ± 2 ly (48.5 ± 0.7 pc) |
| Absolute magnitude (MV) | +1.87[5] |
| Details | |
| Mass | 1.93[6] M☉ |
| Luminosity | 14[7] L☉ |
| Surface gravity (log g) | 4.07±0.14[6] cgs |
| Temperature | 8,113±276[6] K |
| Rotational velocity (v sin i) | 45.2±0.5[8] km/s |
| Age | 809[6] Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
Theta2 Sagittarii, Latinized from θ2 Sagittarii, is a solitary[10] star in the zodiac constellation of Sagittarius. It is faintly visible to the naked eye with an apparent visual magnitude of +5.30.[2] The star is progressing in the general direction of the Sun with a radial velocity of −17.60 km/s.[4] Based upon an annual parallax shift of 20.62 mas as seen from Earth,[1] it is located around 158 light years from the Sun. The star is drifting closer with a radial velocity of −17.6 km/s.[4]
The spectrum of Theta2 Sagittarii matches a stellar classification of A4/A5 IV,[3] indicating that, at the estimated age of 809 million years,[6] this is an evolving A-type subgiant star. It is a suspected Am star and may display photometric variability, at least during a 1992 observation period.[11] The star has an estimated 1.93[6] times the mass of the Sun and is radiating 14[7] times the Sun's luminosity from its photosphere at an effective temperature of 8,113 K.[6] It is spinning with a projected rotational velocity of 45.2 km/s.[8]
Theta2 Sagittarii has a pair of visual companions. Component B is a magnitude 11.3 star at an angular separation of 32.8 arc seconds along a position angle of 165°, as of 2000. Component C lies at an angular separation of 1.5 arc seconds along a position angle of 104° from component B, as of 1965.[12] Neither is physically associated with Theta2 Sagittarii itself.[10]
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