Delta Sagittae

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Delta Sagittae
Diagram showing star positions and boundaries of the Sagitta constellation and its surroundings
Cercle rouge 100%.svg

Location of δ Sagittae (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Sagitta
Right ascension 19h 47m 23.26253s[1]
Declination +18° 32′ 03.4401″[1]
Apparent magnitude (V) +3.82[2]
(3.91[3] / 6.64)[4]
Spectral type M2II + B9.5V[4]
U−B color index +0.98[5]
B−V color index +1.40[5]
Radial velocity (Rv) 2.5 ± 0.9[6] km/s
Proper motion (μ) RA: -4.31[1] mas/yr
Dec.: 12.35[1] mas/yr
Parallax (π) 5.49 ± 0.72[1] mas
Distance approx. 590 ly
(approx. 180 pc)
Period (P) 10.11 yr
Semi-major axis (a) 0.051″
Eccentricity (e) 0.44
Inclination (i) 140.0°
Longitude of the node (Ω) 170.2°
Periastron epoch (T) 1979.93
Argument of periastron (ω)
δ Sge A
Mass 3.35+0.335
[7] M
Radius 129+13
[7] R
Luminosity 2500[7] L
Surface gravity (log g) 0.74 ± 0.10[7] cgs
Temperature 3600+288
[7] K
δ Sge B
Mass 2.9[4] M
Radius 2.6[4] R
Luminosity 63[4] L
Temperature 10000[4] K
Other designations
δ Sagittae, 7 Sagittae, BD+18 4240, CCDM J19474+1832AB, FK5 743, GC 27391, HD 187076, HIP 97365, HR 7536, IDS 19429+1817 AB, PPM 136976, SAO 105259, WDS J19474+1832AB
Database references

Delta Sagittae (Delta Sge, δ Sagittae, δ Sge) is a binary star in the constellation of Sagitta, with an apparent magnitude of +3.68. The primary component is a red M-type bright giant, and the secondary is a B-type main-sequence star.[2] It is approximately 590 light years from Earth, based on its parallax.[1]

Delta Sagittae is a spectroscopic binary with a composite spectrum, meaning that light from both stars can be detected. It has an orbital period of about 10 years and an eccentricity of about 0.44.[4]

Delta Sagittae is moving through the Galaxy at a speed of 9.8 km/s relative to the Sun. Its projected Galactic orbit carries it between 23,800 and 35,300 light years from the center of the Galaxy.[8]


In Chinese, 左旗 (Zuǒ Qí), meaning Left Flag, refers to an asterism consisting of δ Sagittae, α Sagittae, β Sagittae, ζ Sagittae, γ Sagittae, 13 Sagittae, 11 Sagittae, 14 Sagittae and ρ Aquilae. Consequently, δ Sagittae itself is known as 左旗三 (Zuǒ Qí sān, English: the Third Star of Left Flag.)[9]


  1. ^ a b c d e f van Leeuwen, F.; et al. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752Freely accessible. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. 
  2. ^ a b "* del Sge". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 23 February 2017. 
  3. ^ Calculated from subtracting magnitudes.
  4. ^ a b c d e f g h Eaton, Joel A.; Hartkopf, William I.; McAlister, Harold A.; Mason, Brian D. (1995). "Winds and accretion in delta Sagittae". Astronomical Journal. 109 (4): 1856–1866. Bibcode:1995AJ....109.1856E. doi:10.1086/117412. 
  5. ^ a b Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Bibcode:1986EgUBV........0M. 
  6. ^ Wilson, Ralph Elmer (1953). "General catalogue of stellar radial velocities". Bibcode:1953GCRV..C......0W. 
  7. ^ a b c d e Schröder, K.-P.; Cuntz, M. (2007). "A critical test of empirical mass loss formulas applied to individual giants and supergiants". Astronomy and Astrophysics. 465 (2): 593–601. arXiv:astro-ph/0702172Freely accessible. Bibcode:2007A&A...465..593S. doi:10.1051/0004-6361:20066633. 
  8. ^ Delta Sagittae (HIP 97365)
  9. ^ (Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 3 日