Beta Sagittae

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β Sagittae
Sagitta constellation map.svg
Red circle.svg
Location of β Sagittae (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Sagitta
Right ascension 19h 41m 02.93907s[1]
Declination +17° 28′ 33.7528″[1]
Apparent magnitude (V) 4.38[2]
Spectral type G8 IIIa CN 0.5[3]
U−B color index +0.89[4]
B−V color index +1.05[4]
R−I color index +0.50[4]
Radial velocity (Rv)−22.0±0.3[5] km/s
Proper motion (μ) RA: 7.682 ± 0.258[6] mas/yr
Dec.: −32.987 ± 0.279[6] mas/yr
Parallax (π)7.7237 ± 0.1941[6] mas
Distance420 ± 10 ly
(129 ± 3 pc)
Absolute magnitude (MV)−1.39+0.22
Mass4.33[8] M
Radius27±3[9] R
Luminosity392[10] L
Surface gravity (log g)2.79[7] cgs
Temperature4,850[7] K
Metallicity [Fe/H]–0.03[7] dex
Rotational velocity (v sin i)9.1±0.7[7] km/s
Age129[11] Myr
Other designations
β Sge, 6 Sagittae, BD+17°4048, FK5 1513, GC 27236, HD 185958, HIP 96837, HR 7488, SAO 105133, PPM 136766[12]
Database references

Beta Sagittae, Latinized from β Sagittae, is a single[13] star in the northern constellation of Sagitta. It is a faint star but visible to the naked eye with an apparent visual magnitude of 4.38.[2] Based upon an annual parallax shift of 7.7237 mas as seen from the Gaia satellite, it is located 420 light years from the Sun. The star is moving closer to the Sun with a radial velocity of −22 km/s.[5]

This is an evolved red giant[11] with a stellar classification of G8 IIIa CN 0.5.[3] The suffix notation indicates a mild overabundance of the cyanogen molecule in the spectrum. Beta Sagittae is an estimated 129 million years old with 4.33 times the mass of the Sun,[8] and has expanded to roughly 27 times the Sun's radius.[9] The star is radiating 392[10] times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,850 K.[7]


In Chinese, 左旗 (Zuǒ Qí), meaning Left Flag, refers to an asterism consisting of β Sagittae, α Sagittae, δ Sagittae, ζ Sagittae, γ Sagittae, 13 Sagittae, 11 Sagittae, 14 Sagittae and ρ Aquilae. Consequently, the Chinese name for β Sagittae itself is 左旗二 (Zuǒ Qí èr, English: the Second Star of Left Flag.)[14]


  1. ^ a b Van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357.
  2. ^ a b Fernie, J. D. (May 1983), "New UBVRI photometry for 900 supergiants", Astrophysical Journal Supplement Series, 52: 7–22, Bibcode:1983ApJS...52....7F, doi:10.1086/190856.
  3. ^ a b Keenan, Philip C.; McNeil, Raymond C. (1989), "The Perkins catalog of revised MK types for the cooler stars", Astrophysical Journal Supplement Series, 71: 245, Bibcode:1989ApJS...71..245K, doi:10.1086/191373.
  4. ^ a b c Hoffleit, D.; Warren, Jr., W. H., The Bright Star Catalogue (5th Revised Ed. (Preliminary Version) ed.), CDS. HR 7488, database entry
  5. ^ a b Gontcharov, G. A. (November 2006), "Pulkovo Compilation of Radial Velocities for 35495 Hipparcos stars in a common system", Astronomy Letters, 32 (11): 759–771, arXiv:1606.08053, Bibcode:2006AstL...32..759G, doi:10.1134/S1063773706110065.
  6. ^ a b c Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  7. ^ a b c d e f Carney, Bruce W.; et al. (March 2008), "Rotation and Macroturbulence in Metal-Poor Field Red Giant and Red Horizontal Branch Stars", The Astronomical Journal, 135 (3): 892–906, arXiv:0711.4984, Bibcode:2008AJ....135..892C, doi:10.1088/0004-6256/135/3/892.
  8. ^ a b Liu, Y. J.; et al. (April 2014), "The Lithium Abundances of a Large Sample of Red Giants", The Astrophysical Journal, 785 (2): 12, arXiv:1404.1687, Bibcode:2014ApJ...785...94L, doi:10.1088/0004-637X/785/2/94, 94.
  9. ^ a b Van Belle, G. T.; et al. (2009), "Supergiant temperatures and linear radii from near-infrared interferometry", Monthly Notices of the Royal Astronomical Society, 394 (4): 1925, arXiv:0811.4239, Bibcode:2009MNRAS.394.1925V, doi:10.1111/j.1365-2966.2008.14146.x.
  10. ^ a b McDonald, I.; et al. (2012), "Fundamental parameters and infrared excesses of Hipparcos stars", Monthly Notices of the Royal Astronomical Society, 427: 343, arXiv:1208.2037, Bibcode:2012MNRAS.427..343M, doi:10.1111/j.1365-2966.2012.21873.x.
  11. ^ a b Takeda, Yoichi; Tajitsu, Akito (2014), "Spectroscopic study on the beryllium abundances of red giant stars", Publications of the Astronomical Society of Japan, 66 (5): 91, arXiv:1406.7066, Bibcode:2014PASJ...66...91T, doi:10.1093/pasj/psu066.
  12. ^ "bet Sge". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-11-26.
  13. ^ Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x.
  14. ^ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 3 日