Xi Serpentis

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Xi Serpentis
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Serpens
Right ascension 17h 37m 35.19983s[1]
Declination −15° 23′ 54.7940″[1]
Apparent magnitude (V) 3.54[2]
Spectral type A9 IIIp Sr[3]
U−B color index +0.12[2]
B−V color index +0.27[2]
Radial velocity (Rv) −42.8±0.7[4] km/s
Proper motion (μ) RA: −42.10[1] mas/yr
Dec.: −59.94[1] mas/yr
Parallax (π) 30.98 ± 0.19[1] mas
Distance 105.3 ± 0.6 ly
(32.3 ± 0.2 pc)
Period (P) 2.2923 d
Eccentricity (e) 0.00
Periastron epoch (T) 2419210.191 JD
Semi-amplitude (K1)
19.4 km/s
ξ Ser Aa
Mass 2.06[6] M
Luminosity 30.6[7] L
Surface gravity (log g) 3.55[3] cgs
Temperature 7,217±41[6] K
Metallicity [Fe/H] +0.07[3] dex
Rotational velocity (v sin i) 54[8] km/s
Age 1.03[6] Gyr
ξ Ser Ab
Mass 0.18[9] M
Other designations
ξ Ser, 55 Ser, BD−15° 4621, FK5 658, HD 159876, HIP 86263, HR 6561, SAO 160700.[10]
Database references

Xi Serpentis (ξ Ser, ξ Serpentis) is a triple star[9] system in the Serpens Cauda (tail) section of the equatorial constellation Serpens. Based upon an annual parallax shift of 30.98 mas as seen from Earth,[1] it is located 105.3 light years from the Sun. The star system is visible to the naked eye with a base apparent visual magnitude of +3.54.[2] It is moving toward the Sun and will make perihelion passage at a distance of 27 ly (8.2 pc) in around 690,000 years.[11]

The inner pair form a single-lined spectroscopic binary with an orbital period of 2.29 days following a circular orbit with an eccentricity of 0.00.[5] The primary, component Aa, has a visual magnitude of 3.54.[12] It is a white-hued G-type giant star with a stellar classification of A9 IIIp Sr.[3] This indicates it is a chemically peculiar Ap star with an abnormal abundance of strontium. The primary has around double[6] the mass of the Sun, while its close companion, component Ab,[12] has only 18%[9] of the Sun's mass.

The third member, component B, is a magnitude 13.0[12] common proper motion companion.[9] As of 2012, it was located at an angular separation of 24 arc seconds along a position angle of 78° from the inner pair.[12] It has about 27% of the Sun's mass and an estimated orbital period of 14,763 years.[9]


In Chinese, Tiān Shì Zuǒ Yuán (天市左垣), meaning Left Wall of Heavenly Market Enclosure, refers to an asterism which is represent eleven old states (and region) in China which is marking the left borderline of the enclosure, consisting of ξ Serpentis, δ Herculis, λ Herculis, μ Herculis, ο Herculis, 112 Herculis, ζ Aquilae, η Serpentis, θ1 Serpentis, ν Ophiuchi and η Ophiuchi.[13] Consequently, ξ Serpentis itself is known as Tiān Shì Zuǒ Yuán shí (天市左垣十, English: the Tenth Star of Left Wall of Heavenly Market Enclosure), representing the region of Nanhai (南海, lit. meaning southern sea)[14][15]


  1. ^ a b c d e f van Leeuwen, F. (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 c d Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV data, SIMBAD, Bibcode:1986EgUBV........0M. 
  3. ^ a b c d Gray, R. O.; et al. (July 2006), "Contributions to the Nearby Stars (NStars) Project: spectroscopy of stars earlier than M0 within 40 pc-The Southern Sample", The Astronomical Journal, 132 (1): 161–170, arXiv:astro-ph/0603770Freely accessible, Bibcode:2006AJ....132..161G, doi:10.1086/504637. 
  4. ^ de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics, 546: 14, arXiv:1208.3048Freely accessible, Bibcode:2012A&A...546A..61D, doi:10.1051/0004-6361/201219219, A61. 
  5. ^ a b Pourbaix, D.; et al. (2004), "SB9: The ninth catalogue of spectroscopic binary orbits", Astronomy and Astrophysics, 424 (2): 727, arXiv:astro-ph/0406573Freely accessible, Bibcode:2004A&A...424..727P, doi:10.1051/0004-6361:20041213. 
  6. ^ a b c d Luck, R. Earle (2015), "Abundances in the Local Region. I. G and K Giants", The Astronomical Journal, 150 (3): 88, arXiv:1507.01466Freely accessible, Bibcode:2015AJ....150...88L, doi:10.1088/0004-6256/150/3/88. 
  7. ^ McDonald, I.; et al. (2012), "Fundamental Parameters and Infrared Excesses of Hipparcos Stars", Monthly Notices of the Royal Astronomical Society, 427 (1): 343–57, arXiv:1208.2037Freely accessible, Bibcode:2012MNRAS.427..343M, doi:10.1111/j.1365-2966.2012.21873.x. 
  8. ^ Royer, F.; et al. (October 2002), "Rotational velocities of A-type stars in the northern hemisphere. II. Measurement of v sin i", Astronomy and Astrophysics, 393: 897−911, arXiv:astro-ph/0205255Freely accessible, Bibcode:2002A&A...393..897R, doi:10.1051/0004-6361:20020943. 
  9. ^ a b c d e Tokovinin, A.; et al. (May 2006), "Tertiary companions to close spectroscopic binaries", Astronomy and Astrophysics, 450 (2): 681–69, arXiv:astro-ph/0601518Freely accessible, Bibcode:2006A&A...450..681T, doi:10.1051/0004-6361:20054427. 
  10. ^ "ksi Ser -- Spectroscopic binary", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2017-03-23. 
  11. ^ Bailer-Jones, C. A. L. (March 2015), "Close encounters of the stellar kind", Astronomy & Astrophysics, 575: 13, arXiv:1412.3648Freely accessible, Bibcode:2015A&A...575A..35B, doi:10.1051/0004-6361/201425221, A35. 
  12. ^ a b c d Mason, B. D.; et al. (2014), The Washington Visual Double Star Catalog, Bibcode:2001AJ....122.3466M, doi:10.1086/323920. 
  13. ^ (Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
  14. ^ (Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 6 月 23 日
  15. ^ (Chinese) English-Chinese Glossary of Chinese Star Regions, Asterisms and Star Name Archived August 10, 2010, at the Wayback Machine., Hong Kong Space Museum. Accessed on line November 23, 2010.