Theta Sagittae (θ Sagittae) is a double star in the northern constellation of Sagitta.[14] With a combined apparent visual magnitude of +6, it is near the limit of stars that can be seen with the naked eye. According to the Bortle scale the star is visible in dark suburban/rural skies. Based upon an annual parallax shift of 22.15 mas as seen from Earth,[15] it is located roughly 147 light years from the Sun.

θ Sagittae

Location of θ Sagittae (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Sagitta
A
Right ascension	20h 09m 56.6470s[1]
Declination	+20° 54′ 54.094″[1]
Apparent magnitude (V)	+6.516[2]
B
Right ascension	20h 09m 56.2405s[3]
Declination	+20° 55′ 04.228″[3]
Apparent magnitude (V)	+8.769[2]
Characteristics
A
Spectral type	F3V[4]
U−B color index	−0.04[5]
B−V color index	+0.38[5]
B
Spectral type	G5V[6]
B−V color index	+0.732[2]
Astrometry
A
Radial velocity (Rv)	−40.92[1] km/s
Proper motion (μ)	RA: +58.387[1] mas/yr Dec.: +98.274[1] mas/yr
Parallax (π)	22.3262 ± 0.0326 mas[1]
Distance	146.1 ± 0.2 ly (44.79 ± 0.07 pc)
Absolute magnitude (MV)	+3.24[7]
B
Radial velocity (Rv)	−43.0[8] km/s
Proper motion (μ)	RA: +64.726[3] mas/yr Dec.: +101.800[3] mas/yr
Parallax (π)	22.3841 ± 0.0305 mas[3]
Distance	145.7 ± 0.2 ly (44.67 ± 0.06 pc)
Absolute magnitude (MV)	+5.58[7]
Details
A
Mass	1.52[9] M☉
Radius	1.45[1] R☉
Luminosity	4.0[1] L☉
Surface gravity (log g)	4.32[9] cgs
Temperature	6,750±229[9] K
Metallicity [Fe/H]	−0.17[8] dex
Rotational velocity (v sin i)	33.6[10] km/s
Age	2.089[9] Gyr
B
Mass	0.95[11] M☉
Radius	0.82[3] R☉
Luminosity	0.516[3] L☉
Surface gravity (log g)	4.526[12] cgs
Temperature	5,394[3] K
Other designations
θ Sge, 17 Sge, BD+20°4453, HD 191570, WDS J20099+2055[13]
A: HIP 99352, HR 7705, SAO 88276
B: HIP 99351, SAO 88275
Database references
SIMBAD	A
	B

The binary pair consists of two stars separated by 502 AU.[16] The primary, component A,[17] is an F-type main sequence star with a stellar classification of F3V.[4] This star is about two billion years old[9] with 52% more mass than the Sun.[9] It forms a double star with a magnitude 8.85 companion,[17] which is located at an angular separation of 11.58 arc seconds along a position angle of 331.1°, as of 2011.[14] The star is sometimes described as a triple star, with a 7th magnitude companion 91″ away.[17] This is an unrelated giant star much further away than the close pair.[18] A fainter star separated by nearly 3′ was also listed as a companion by Struve,[17] again just an accidental optical association.[19]

References