Theta2 Sagittarii

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]

For other stars with this Bayer designation, see θ Sagittarii.

Theta² Sagittarii

Location of θ2 Sagittarii (circled)
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
θ2 Sgr, CPD−35°8701, HD 189118, HIP 98421, HR 7624, SAO 211717, WDS J19599-3442[9]
Database references
SIMBAD	data

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]