Theta Sagittarii

Theta² Sagittarii

Location of θ² Sagittarii (circled)

Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Sagittarius
Right ascension	19^h 59^m 51.3^s
Declination	−34° 41' 52"
Apparent magnitude (V)	+5.30
Distance	157 ± 7 ly (48 ± 2 pc)
Spectral type	A4/A5IV
Other designations
θ² Sagittarii, θ² Sgr, Theta² Sgr, CCDM J19599-3442A, CPD-35  8701, GC 27676, HD 189118, HIP 98421, HR 7624, IDS 19534-3458 A, PPM 299635, SAO 211717

Theta¹ Sagittarii

Location of θ¹ Sagittarii (circled)

Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Sagittarius
Right ascension	19^h 59^m 44.2^s
Declination	−35° 16' 35"
Apparent magnitude (V)	+4.37
Distance	618 ± 105 ly (189 ± 32 pc)
Spectral type	B2.5IV
Other designations
θ¹ Sagittarii, θ¹ Sgr, Theta¹ Sgr, CPD-35 8699, FK5 751, GC 27670, HD 189103, HIP 98412, HR 7623, PPM 299634, SAO 211716.

The Bayer designation Theta Sagittarii (Theta Sgr, θ Sagittarii, θ Sgr) is shared by two star systems, θ¹ Sagittarii and θ² Sagittarii, in the constellation Sagittarius. The two stars are separated by 0.58° in the sky.

θ¹ Sagittarii

Theta¹ Sagittarii (Theta¹ Sgr, θ¹ Sagittarii, θ¹ Sgr) is a spectroscopic binary lying 617 light years from Earth. The primary star, θ¹ Sagittarii A, is a spectral type B2.5 subgiant which has an apparent magnitude of +4.37. The companion star, θ¹ Sagittarii B, is approximately 0.2 arcseconds from the primary, which puts them 31 astronomical units (AU) apart (a Sun-Neptune distance).

Theta¹ Sagittarii is moving through the Galaxy at a speed of 19.9 km/s relative to the Sun. Its projected Galactic orbit carries it between 20,900 and 24,300 light years from the center of the Galaxy.^[1]

θ² Sagittarii

Theta² Sagittarii (Theta² Sgr, θ² Sagittarii, θ² Sgr) is a triple star system 157 light years from Earth. θ² Sagittarii A is a spectral type A4/5 subgiant which has an apparent magnitude of +5.30. Orbiting the primary with a separation on the sky of 30 arcseconds, or at least 1400 AU, is binary star composed of θ² Sagittarii B, a magnitude +10.8 star, and θ² Sagittarii C, with a magnitude of +11.5. B and C are 1.2 arcseconds, or approximately 58 AU apart.

Theta² Sagittarii is moving through the Galaxy at a speed of 34.6 km/s relative to the Sun. Its projected Galactic orbit carries it between 22,800 and 26,100 light years from the center of the Galaxy.^[2]

References

1. Theta-1 Sagittarii (HIP 98412)
2. Theta-2 Sagittarii (HIP 98421)