Delta Serpentis

Delta Serpentis, Latinized from δ Serpentis, is a hierarchical triple star system in the constellation Serpens, in its head (Serpens Caput). The light from the two stars in the system give a combined apparent magnitude of +3.80, which is bright enough to be visible to the naked eye. Based on parallax measurements, it is located at a distance of approximately 230 light years from the Sun. The system is moving closer with a radial velocity of ~42 km/s, and may come to within in 1.2 million years.

The primary, component Aa, is a yellow-white F-type subgiant, two times more massive than the Sun, but with 4.6 times the Sun's radius. It is classified as a Delta Scuti type variable star and its magnitude varies by 0.04 with a period of 0.1557 days. It forms a small pair with Ab, a star of undefined spectral type, with a mass 1.8 times the Sun's mass and a radius 2.5 times larger. Both are separated by and complete an orbit around each other every . They are visible with a combined apparent magnitude of +4.25. The outer, component B, is also an F-type subgiant which is slightly dimmer, with a magnitude of +5.2. A and B are separated by four arcseconds in the sky, and perform one orbit around their centre of mass once every 3,200 years.

Naming

It was a member of the indigenous Arabic asterism al-Nasaq al-Yamānī, "the Southern Line" of al-Nasaqān "the Two Lines", along with α Ser (Unukalhai), ε Ser (Ba), δ Oph (Yed Prior), ε Oph (Yed Posterior), ζ Oph (Han) and γ Oph (Bake-eo).

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 (excluding α Ser, δ Oph, ε Oph, ζ Oph and γ Oph).

In Chinese, (), 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 δ Serpentis, β Herculis, γ Herculis, κ Herculis, γ Serpentis, β Serpentis, α Serpentis, ε Serpentis, δ Ophiuchi, ε Ophiuchi and ζ Ophiuchi. Consequently, the Chinese name for δ Serpentis itself is (, ), representing the state Qin (秦) (or Tsin), together with θ Capricorni and 30 Capricorni (according to Ian Ridpath version) in Twelve States (asterism).

References