Epsilon Serpentis

ε Serpentis
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Serpens
Right ascension 15h 50m 49.0s
Declination +04° 28 40
Apparent magnitude (V) +3.71
Absolute magnitude (V)+2.04
Distance70.3 ± 1.1 ly
(21.6 ± 0.3 pc)
Spectral typeA2Vm
Other designations
37 Serpentis, HR 5892, HD 141795, SAO 121218, HIP 77622

Epsilon Serpentis (ε Ser, ε Serpentis) is a star in the constellation Serpens, in its head (Serpens Caput).


It was a member of indigenous Arabic asterism al-Nasaq al-Yamānī, "the Southern Line" of al-Nasaqān "the Two Lines".,[1] along with α Ser (Unukalhai), δ Ser (Qin, Tsin), δ Oph (Yed Prior), ε Oph (Yed Posterior), ζ Oph (Han) and γ Oph (Tsung Ching).[2]

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)[3]

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.[4] Consequently, ε Serpentis itself is known as 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).[5][6][7]


Epsilon Serpentis is a white A-type main sequence dwarf with an apparent magnitude of +3.71. It is approximately 70.3 light years from Earth. This star has 1.8 times the Sun's radius and it is radiating 12 times the luminosity of the Sun from its outer envelope at an effective temperature of 8,084 K.[8]


  1. 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.
  2. 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.
  3. Jack W. Rhoads - Technical Memorandum 33-507-A Reduced Star Catalog Containing 537 Named Stars, Jet Propulsion Laboratory, California Institute of Technology; November 15, 1971
  4. (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.
  5. Star Names - R.H.Allen p.376
  6. (Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 6 月 24 日
  7. (Chinese) English-Chinese Glossary of Chinese Star Regions, Asterisms and Star Name, Hong Kong Space Museum. Accessed on line November 23, 2010.
  8. 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:1112.3316Freely accessible, Bibcode:2012ApJ...746..101B, doi:10.1088/0004-637X/746/1/101. See Table 10.
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