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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