Alpha Sagittae

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

Location of α Sagittae (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Sagitta
Right ascension 19h 40m 05.8s [1]
Declination +18° 00′ 50″ [1]
Apparent magnitude (V) +4.39[2]
Evolutionary stage G1II[2]
Radial velocity (Rv) 1.72 ± 0.16[1] km/s
Proper motion (μ) RA: 15.09 ± 0.16[3] mas/yr
Dec.: -19.65 ± 0.15[3] mas/yr
Parallax (π) 7.67 ± 0.24[3] mas
Distance 430 ± 10 ly
(130 ± 4 pc)
Other designations
Sham, Alsahm, α Sagittae, α Sge, Alpha Sge, 5 Sagittae, BD+17°4042, CCDM J19401+1801A, GC 27215, HD 185758, HIP 96757, HR 7479, IDS 19356+1747 A, PPM 136737, SAO 105120, WDS J19401+1801A

Alpha Sagittae (Alpha Sge, α Sagittae, α Sge) is a star in the constellation Sagitta. It has the traditional proper name Sham or Alsahm which comes from the Arabic word سهم sahm and means Arrow, the name formerly having been applied to the whole constellation. Alpha Sagittae is the third brightest star and is four times more massive and 340 times brighter than the Sun.[4]

In Chinese, 左旗 (Zuǒ Qí), meaning Left Flag, refers to an asterism consisting of α Sagittae, β Sagittae, δ Sagittae, ζ Sagittae, γ Sagittae, 13 Sagittae, 11 Sagittae, 14 Sagittae and ρ Aquilae. Consequently, α Sagittae itself is known as 左旗一 (Zuǒ Qí yī, English: the First Star of Left Flag.)[5]

α Sge is a yellow bright giant star of apparent magnitude +4.38 and spectral class G1 II about 430 ± 10 light years from Earth. It has a luminosity 340 times that of the Sun with a surface temperature of 5,333 K.[2] The star's radius is roughly 20 times solar (R) while its mass is 4 times solar (M).


  1. ^ a b c SIMBAD, Alpha Sagittae (accessed 22 May 2015)
  2. ^ a b c Mallik, Sushma V. (December 1999), "Lithium abundance and mass", Astronomy and Astrophysics, 352: 495–507, Bibcode:1999A&A...352..495M 
  3. ^ a b c van Leeuwen, F. (2007). "Validation of the New Hipparcos Reduction". Astronomy and Astrophysics. 474 (2): 653–64. arXiv:0708.1752free to read. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. 
  4. ^ "Sagitta". Retrieved 2012-05-23. 
  5. ^ (Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 3 日