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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.
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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.
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.