Epsilon Serpentis

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Epsilon Serpentis
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Serpens
Right ascension  15h 50m 48.96622s[1]
Declination +04° 28′ 39.8311″[1]
Apparent magnitude (V) +3.69[2]
Spectral type kA2hA5mA7 V[3]
U−B color index +0.12[2]
B−V color index +0.14[2]
Radial velocity (Rv)−9.4±0.6[4] km/s
Proper motion (μ) RA: +128.19[1] mas/yr
Dec.: +62.16[1] mas/yr
Parallax (π)46.30 ± 0.19[1] mas
Distance70.4 ± 0.3 ly
(21.60 ± 0.09 pc)
Absolute magnitude (MV)+2.04[5]
Mass1.820±0.026[6] M
Radius1.783±0.040[6] R
Luminosity12.134±0.296[6] L
Surface gravity (log g)4.346[7] cgs
Temperature7,928±88[7] K
Metallicity [Fe/H]+0.38[7] dex
Rotational velocity (v sin i)33.1[7] km/s
Age500±200[6] Myr
Other designations
ε Ser, 37 Serpentis, HD 141795, HIP 77622, HR 5892, SAO 121218[8]
Database references

Epsilon Serpentis, Latinized from ε Serpentis, is a single,[9] white-hued star in the constellation Serpens, in its head (Serpens Caput). It is visible to the naked eye with an apparent visual magnitude of +3.69.[2] Based upon an annual parallax shift of 46.30 mas as seen from Earth,[1] it is located 70 light years from the Sun. It is moving closer to the Sun with a radial velocity of −9 km/s.[4]

This is an Am star[10] on the main-sequence with a stellar classification of kA2hA5mA7 V.[3] This notation indicates the spectrum displays the calcium K-line of an A2 star, the hydrogen lines of an A5 star, and the metal lines of an A7 star.[11] It has been examined for the presence of a magnetic field, but the detected level was not statistically significant.[12]

Epsilon Serpentis has an estimated 1.82 times the mass of the Sun and 1.78 times the Sun's radius.[6] The star is radiating 12[6] times the Sun's luminosity from its photosphere at an effective temperature of around 7,928 K.[7] It is a candidate for an infrared excess at a wavelength of 25 μm, suggesting a circumstellar disk of dust with a temperature of 250±70 K may be orbiting roughly 4.2 AU from the host star.[13] The star is around half[6] a billion years old and is spinning with a projected rotational velocity of 33.1 km/s.[7]


Epsilon Serpentis was a member of indigenous Arabic asterism al-Nasaq al-Yamānī, "the Southern Line" of al-Nasaqān "the Two Lines".[14] along with α Ser (Unukalhai), δ Ser, δ Oph (Yed Prior), ε Oph (Yed Posterior), ζ Oph and γ Oph.[15]

According to the catalogue of stars in the Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars, al-Nasaq al-Yamānī or Nasak Yamani were the title for two stars :δ Ser as Nasak Yamani I and ε Ser as Nasak Yamani II (exclude α Ser, δ Oph, ε Oph, ζ Oph and γ Oph).[16]

In Chinese, 天市右垣 (Tiān Shì Yòu Yuán), meaning Right Wall of Heavenly Market Enclosure, refers to an asterism which is represent eleven old states in China which is marking the right borderline of the enclosure, consisting of ε Serpentis, β Herculis, γ Herculis, κ Herculis, γ Serpentis, β Serpentis, α Serpentis, δ Serpentis, δ Ophiuchi, ε Ophiuchi and ζ Ophiuchi.[17] Consequently, the Chinese name for ε Serpentis itself is 天市右垣八 (Tiān Shì Yòu Yuán bā, English: the Eighth Star of Right Wall of Heavenly Market Enclosure), represent the state Ba (巴) (or Pa).[18][19][20]


  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:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357.
  2. ^ a b c d Feinstein, A. (1974), "Photoelectric UBVRI observations of Am stars", Astronomical Journal, 79: 1290, Bibcode:1974AJ.....79.1290F, doi:10.1086/111675.
  3. ^ a b 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/0603770, Bibcode:2006AJ....132..161G, doi:10.1086/504637.
  4. ^ a b 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:1208.3048, Bibcode:2012A&A...546A..61D, doi:10.1051/0004-6361/201219219, A61.
  5. ^ Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015.
  6. ^ a b c d e f g Boyajian, Tabetha S.; et al. (February 2012), "Stellar Diameters and Temperatures. I. Main-sequence A, F, and G Stars", The Astrophysical Journal, 746 (1): 101, arXiv:1112.3316, Bibcode:2012ApJ...746..101B, doi:10.1088/0004-637X/746/1/101.. See Table 10.
  7. ^ a b c d e f David, Trevor J.; Hillenbrand, Lynne A. (2015), "The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets", The Astrophysical Journal, 804 (2): 146, arXiv:1501.03154, Bibcode:2015ApJ...804..146D, doi:10.1088/0004-637X/804/2/146.
  8. ^ "eps Ser". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-09-26.
  9. ^ Rodriguez, David R.; et al. (May 2015), "Stellar multiplicity and debris discs: an unbiased sample", Monthly Notices of the Royal Astronomical Society, 449 (3): 3160–3170, arXiv:1503.01320, Bibcode:2015MNRAS.449.3160R, doi:10.1093/mnras/stv483.
  10. ^ Adelman, Saul J.; Albayrak, Berahitdin (October 1998), "Elemental abundance analyses with DAO spectrograms - XX", Monthly Notices of the Royal Astronomical Society, 300 (2): 359–372, Bibcode:1998MNRAS.300..359A, doi:10.1046/j.1365-8711.1998.01859.x
  11. ^ Walker, Richard (2017), Spectral Atlas for Amateur Astronomers: A Guide to the Spectra of Astronomical Objects and Terrestrial Light Sources, Cambridge University Press, p. 116, ISBN 1316738760.
  12. ^ Shorlin, S. L. S.; et al. (September 2002), "A highly sensitive search for magnetic fields in B, A and F stars", Astronomy and Astrophysics, 392: 637–652, Bibcode:2002A&A...392..637S, doi:10.1051/0004-6361:20021192.
  13. ^ Smith, R.; Wyatt, M. C. (June 2010), "Warm dusty discs: exploring the A star 24 μm debris population", Astronomy and Astrophysics, 515: 16, arXiv:1004.0644, Bibcode:2010A&A...515A..95S, doi:10.1051/0004-6361/200913481, A95.
  14. ^ Kunitzsch, P., Smart, T. (2006), A Dictionary of Modern Star names: A Short Guide to 254 Star names and Their Derivations (Second Revised ed.), Cambridge, MA: Sky Publishing, p. 31, ISBN 1-931559-44-9.
  15. ^ Allen, R. H. (1963). Star Names: Their Lore and Meaning (Reprint ed.). New York, NY: Dover Publications Inc. p. 243. ISBN 0-486-21079-0. Retrieved 2010-12-12.
  16. ^ Rhoads, Jack W. (November 15, 1971), Technical Memorandum 33-507-A Reduced Star Catalog Containing 537 Named Stars (PDF), Jet Propulsion Laboratory, California Institute of Technology.
  17. ^ (in 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.
  18. ^ Allen, Richard Hinckley (1963), "Serpens", Star Names, p. 376
  19. ^ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 6 月 24 日
  20. ^ (in 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.