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Epoch J2000.0 Equinox J2000.0
|Right ascension||15h 34m 48.1s|
|Declination||+10° 32' 15"|
|Apparent magnitude (V)||combined: +3.80
AB: 4.2 + 5.2
CD: 14.7 + 15.2
|Distance||210 ± 11 ly
(64 ± 3 pc)
|Spectral type||AB: F0IV + F0IV|
Delta Serpentis (δ Serpentis, δ Ser) is a star system 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"., along with α Ser (Unukalhai), ε Ser (Ba, Pa), δ Oph (Yed Prior), ε Oph (Yed Posterior), ζ Oph (Han) and γ Oph (Tsung Ching).
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)
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 δ Serpentis, β Herculis, γ Herculis, κ Herculis, γ Serpentis, β Serpentis, α Serpentis, ε Serpentis, δ Ophiuchi, ε Ophiuchi and ζ Ophiuchi. Consequently, δ Serpentis itself is known as 天市右垣六 (Tiān Shì Yòu Yuán liù, English: the Sixth Star of Right Wall of Heavenly Market Enclosure), represent the state Qin (秦) (or Tsin), together with θ Capricorni and 30 Capricorni in Twelve States (asterism).
The system consists of a pair of binary stars separated by 66 arcseconds. The primary component, Delta Serpentis A, is a yellow-white F-type subgiant with an apparent magnitude of +4.2. It is classified as a Delta Scuti type variable star and its magnitude varies by 0.04 with a period of 0.134 days. Its binary companion, Delta Serpentis B, is also a F-type subgiant which is slightly dimmer, with a magnitude of +5.2. A and B are separated by four arcseconds on the sky, and perform one orbit around their centre of mass once every 3200 years. The 14th magnitude stars Delta Serpentis C and 15th magnitude Delta Serpentis D form the second binary sub-system. They are separated from each other by 4.4 arcseconds.
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