Astronomy:Alpha Sagittae

From HandWiki
Short description: Star in the constellation Sagitta
α Sagittae
Location of α Sagittae (circled)
Observation data
Equinox J2000.0]] (ICRS)
Constellation Sagitta
Right ascension  19h 40m 05.79185s[1]
Declination +18° 00′ 50.0046″[1]
Apparent magnitude (V) +4.38[2]
Characteristics
Evolutionary stage Red clump[3]
Spectral type G1 II[4]
B−V color index 0.777±0.014[5]
Astrometry
Radial velocity (Rv)+1.72±0.16[6] km/s
Proper motion (μ) RA: +14.630±0.257[1] mas/yr
Dec.: −20.160±0.276[1] mas/yr
Parallax (π)8.5307 ± 0.1848[1] mas
Distance382 ± 8 ly
(117 ± 3 pc)
Absolute magnitude (MV)−0.96[7]
Details
Mass2.95[3] M☉
Radius17.89±0.57[8] R☉
Luminosity340[4] L☉
Surface gravity (log g)2.36±0.07[3] cgs
Temperature5,630±45[3] K
Metallicity [Fe/H]+0.03±0.06[3] dex
Rotational velocity (v sin i)10[9] km/s
Age151[10] Myr
Other designations
Sham, Alsahm, α Sge, 5 Sagittae, BD+17°4042, FK5 1133, GC 27215, HD 185758, HIP 96757, HR 7479, SAO 105120, PPM 136737, CCDM J19401+1801A, WDS J19401+1801A[11]
Database references
SIMBADdata

Alpha Sagittae, formally named Sham /ˈʃæm/,[12][13] is a single[14] star in the northern constellation of Sagitta. Alpha Sagittae is the Bayer designation, which is latinized from α Sagittae and abbreviated Alpha Sge or α Sge. It is visible to the naked eye as a yellow-hued star with an apparent visual magnitude of +4.38.[2] Despite the name, this is not the brightest star in the constellation – that distinction belongs to Gamma Sagittae. Based upon parallax measurements, Alpha Sagittae is approximately 382 light-years from the Sun. It is moving further away from the Earth with a heliocentric radial velocity of 1.7 km/s.[6]

This is an evolved bright giant with a stellar classification of G1 II.[4] It is 151 million years old[10] with 2.95 times the mass of the Sun[3] and has expanded to around 17.9 times the Sun's radius.[8] It is radiating 340 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 5,630 K.[3] There is an X-ray source within 12″ of these coordinates.[15]

The evolutionary state of Alpha Sagittae has been historically unclear. Its temperature and luminosity place it within the Hertzsprung gap, a region of the H-R diagram where stars more massive than the sun are evolving rapidly away from the main sequence towards becoming red giants. However, the chemical composition of its surface indicates that it has already experienced the first dredge-up of fusion products that occurs soon after a star reaches the red giant branch. It also lies within the Cepheid instability strip, but is not a Cepheid variable.[16] It belongs to a small group of known stars that have been called carbon-deficient red giants and may have experienced binary mass exchanges.[17] A 2025 publication concluded that the star is on the horizontal branch, based on its location on the temperature-surface gravity diagram and abundances of carbon and oxgen.[3]

Nomenclature

This star bore the traditional name Sham (or Alsahm), which derives from the Arabic word سهم sahm, meaning "arrow", the name formerly having been applied to the whole constellation. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[18] to catalogue and standardize proper names for stars. The WGSN approved the name Sham for this star on 12 September 2016 and it is now so included in the List of IAU-approved Star Names.[13]

In Chinese, 左旗 (Zuǒ Qí), meaning Left Flag, refers to an asterism consisting of Alpha Sagittae, Beta Sagittae, Delta Sagittae, Zeta Sagittae, Gamma Sagittae, 13 Sagittae, 11 Sagittae, 14 Sagittae and Rho Aquilae. Consequently, the Chinese name for Alpha Sagittae itself is 左旗一 (Zuǒ Qí yī, English: the First Star of Left Flag).[19]

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 Brown, A. G. A. (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics 616: A1. doi:10.1051/0004-6361/201833051. Bibcode: 2018A&A...616A...1G.  Gaia DR2 record for this source at VizieR.
  2. ↑ 2.0 2.1 Høg, E. (2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics 355: L27–L30. Bibcode: 2000A&A...355L..27H. 
  3. ↑ 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 Bale, B.; Tautvaišienė, G.; Minkevičiūtė, R.; Drazdauskas, A.; Mikolaitis, Š; Stonkutė, E.; Ambrosch, M. (2025-11-01). "Chromospherically active stars: Lithium and CNO abundances in northern RS CVn stars" (in en). Astronomy & Astrophysics 703: A128. doi:10.1051/0004-6361/202556683. ISSN 0004-6361. Bibcode: 2025A&A...703A.128B. 
  4. ↑ 4.0 4.1 4.2 Mallik, Sushma V. (December 1999). "Lithium abundance and mass". Astronomy and Astrophysics 352: 495–507. Bibcode: 1999A&A...352..495M. 
  5. ↑ Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters 38 (5): 331. doi:10.1134/S1063773712050015. Bibcode: 2012AstL...38..331A. 
  6. ↑ 6.0 6.1 Soubiran, C.; Bienaymé, O.; Mishenina, T. V.; Kovtyukh, V. V. (2008). "Vertical distribution of Galactic disk stars. IV. AMR and AVR from clump giants". Astronomy and Astrophysics 480 (1): 91–101. doi:10.1051/0004-6361:20078788. Bibcode: 2008A&A...480...91S. 
  7. ↑ Kovtyukh, V. V.; Gorlova, N. I.; Belik, S. I. (2012). "Accurate luminosities from the oxygen λ7771-4 Å triplet and the fundamental parameters of F-G supergiants". Monthly Notices of the Royal Astronomical Society 423 (4): 3268. doi:10.1111/j.1365-2966.2012.21117.x. Bibcode: 2012MNRAS.423.3268K. 
  8. ↑ 8.0 8.1 Baines, Ellyn K. et al. (May 7, 2025). "Vintage NPOI: New and Updated Angular Diameters for 145 Stars" (in en). The Astronomical Journal 169 (6): 293. doi:10.3847/1538-3881/adc930. ISSN 1538-3881. Bibcode: 2025AJ....169..293B. 
  9. ↑ Böhm-Vitense, Erika (November 2004). "Rotation and Lithium Surface Abundances, Revisited". The Astronomical Journal 128 (5): 2435−2442. doi:10.1086/425053. Bibcode: 2004AJ....128.2435B. 
  10. ↑ 10.0 10.1 Takeda, Yoichi; Sato, Bun'ei; Murata, Daisuke (2008). "Stellar Parameters and Elemental Abundances of Late-G Giants". Publications of the Astronomical Society of Japan 60 (4): 781. doi:10.1093/pasj/60.4.781. Bibcode: 2008PASJ...60..781T. 
  11. ↑ "5 Sge". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=5+Sge. 
  12. ↑ Kunitzsch, Paul; Smart, Tim (2006). A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations (2nd rev. ed.). Cambridge, Massachusetts: Sky Pub. ISBN 978-1-931559-44-7. 
  13. ↑ 13.0 13.1 "Naming Stars". IAU.org. https://www.iau.org/public/themes/naming_stars/. Retrieved 16 December 2017. 
  14. ↑ 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. doi:10.1111/j.1365-2966.2008.13596.x. Bibcode: 2008MNRAS.389..869E. 
  15. ↑ Greiner, J.; Richter, G. A. (March 2015). "Optical counterparts of ROSAT X-ray sources in two selected fields at low vs. high Galactic latitudes". Astronomy & Astrophysics 575: 67. doi:10.1051/0004-6361/201322844. A42. Bibcode: 2015A&A...575A..42G. 
  16. ↑ Vanture, Andrew D.; Wallerstein, George (1999). "Carbon, Nitrogen, and Oxygen Abundances of Selected Stars in the Hertzsprung Gap". Publications of the Astronomical Society of the Pacific 111 (755): 84. doi:10.1086/316306. Bibcode: 1999PASP..111...84V. 
  17. ↑ Bond, Howard E. (2019). "Carbon-deficient Red Giants". The Astrophysical Journal 887 (1): 12. doi:10.3847/1538-4357/ab4e13. Bibcode: 2019ApJ...887...12B. 
  18. ↑ "IAU Working Group on Star Names (WGSN)". International Astronomical Union. https://www.iau.org/science/scientific_bodies/working_groups/280/. Retrieved 22 May 2016. 
  19. ↑ Script error: The function "in_lang" does not exist. AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 3 日



Retrieved from "https://handwiki.org/wiki/index.php?title=Astronomy:Alpha_Sagittae&oldid=4214871"