| Observation data Epoch J2000.0 Equinox J2000.0 |
|
|---|---|
| Constellation | Serpens |
| Right ascension | 15h 44m 16.1s |
| Declination | +06° 25' 32" |
| Apparent magnitude (V) | +2.63 |
| Distance | 73.2 ± 1.2 ly (22.5 ± 0.4 pc) |
| Spectral type | K2III |
| Other designations | |
Alpha Serpentis (α Serpentis, α Ser) is a triple star system in the constellation Serpens, in its head (Serpens Caput). Alpha Serpentis has the proper names Unukalhai,[1] from the Arabic عنق الحية ‘Unuq al-Ħayyah "the Serpent's Neck", and Cor Serpentis from the Latin "the Heart of the Serpent". It was a member of the indigenous Arabic asterism al-Nasaq al-Yamānī, "the Southern Line" of al-Nasaqān "the Two Lines".[2] It was a member of indigenous Arabic asterism al-Nasaq al-Yamānī, "the Southern Line" of al-Nasaqān "the Two Lines".,[3] along with δ Ser (Qin, Tsin), ε Ser (Ba, Pa), δ Oph (Yed Prior), ε Oph (Yed Posterior), ζ Oph (Han) and γ Oph (Tsung Ching).[4]
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 this star, δ Oph, ε Oph, ζ Oph and γ Oph)[5]
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 α Serpentis, β Herculis, γ Herculis, κ Herculis, γ Serpentis, β Serpentis, δ Serpentis, ε Serpentis, δ Ophiuchi, ε Ophiuchi and ζ Ophiuchi.[6] Consequently, α Serpentis itself is known as 天市右垣七 (Tiān Shì Yòu Yuán qī, English: the Seventh Star of Right Wall of Heavenly Market Enclosure), represent the state Shu (蜀) (or Shuh)[7][8](together with λ Ser in R.H.Allen's works).[9]
Alpha Serpentis is approximately 70 light years from the Earth and is the brightest star in Serpens.
The primary star, Alpha Serpentis A is an orange K-type giant with an apparent magnitude of +2.63. It has a total luminosity of 70 times solar and a surface temperature of 4300 kelvins. The radius of the star is some 15 times as large as that of the Sun. The magnitude +11.8 Alpha Serpentis B is 58 arcseconds from the primary, and the 13th magnitude Alpha Serpentis C lies 2.3 arcminutes from A.
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