Beta Serpentis, Latinized from β Serpentis, also named Zhou,[ system in the constellation Serpens, in its head (Serpens Caput). It is visible to the naked eye with a combined apparent visual magnitude of +3.65.][ Based upon an annual stellar parallax of 21.03 milliarcsecond as seen from Earth,][ it is located around 155 from the Sun. The system is a member of the Ursa Major Moving Group.][
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Components
The visual magnitude +3.68 primary, component A, is either an ordinary A-type main-sequence star or somewhat evolved subgiant with a stellar classification of A2 V[ or A2 IV,][ respectively. The star is about 610 million years old with 1.8 the mass of the Sun. It is spinning rapidly with a projected rotational velocity of 216.6 km/s, which causes it to have an oblate shape, as well as hotter temperatures in the poles due to gravity darkening. The equatorial radius measures and has an effective temperature of 6,967 Kelvin, while the polar radius measures and has an effective temperature of 9,359 K.][
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The secondary component, visual magnitude 9.7 B, lies at an angular separation of 30.6 . It is a main-sequence star with a class of K3 V.[
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There is a magnitude +10.98 visual companion, designated component C, located 202 away.[
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Nomenclature
It was a member of the indigenous Arabic asterism al-Nasaq al-Sha'āmī, "the Northern Line" of al-Nasaqān "the Two Lines",[ along with Beta Herculis (Kornephoros), Gamma Herculis (Hejian) and Gamma Serpentis (Zheng).][
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According to the catalogue of stars in the Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars, al-Nasaq al-Sha'āmī or Nasak Shamiya was the title for three stars: β Ser as Nasak Shamiya I, Gamma Serpentis as Nasak Shamiya II, Gamma Herculis as Nasak Shamiya III (excluding Beta Herculis).[
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In Chinese, 天市右垣 (Tiān Shì Yòu Yuán), meaning Right Wall of Heavenly Market Enclosure, refers to an asterism which represents eleven old states in China and which marks the right borderline of the enclosure, consisting of β Serpentis, Beta Herculis, Gamma Herculis, Kappa Herculis, Gamma Serpentis, Delta Serpentis, Alpha Serpentis, ε Serpentis, Delta Ophiuchi, Epsilon Ophiuchi and Zeta Ophiuchi.[ 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, .] Consequently, the Chinese name for β Serpentis itself is 天市右垣五 (Tiān Shì Yòu Yuán wu, ), representing Zhou dynasty (周, the dynasty in China),[ AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 6 月 24 日 ][ English-Chinese Glossary of Chinese Star Regions, Asterisms and Star Name , Hong Kong Space Museum. Accessed on line November 23, 2010.] together with Eta Capricorni and 21 Capricorni in Twelve States (asterism).[
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In R. H. Allen's 1899 book Star Names, this Chinese name was transliterated as Chow,[ and this spelling has been used into the 21st century,][ but the pinyin transliteration is Zhou.]
