Delta Serpentis, Latinized from δ Serpentis, is a binary star system in the constellationSerpens, in its head (Serpens Caput). The light from the two stars in the system give a combined apparent magnitude of +3.80,[3] 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.[2] The system is moving closer with a radial velocity of ~42 km/s, and may come to within 115 light-years in 1.2 million years.[3]
The primary, component A, is a yellow-white F-typesubgiant with an apparent magnitude of +4.25. It is classified as a Delta Scuti typevariable star and its magnitude varies by 0.04 with a period of 0.1557 days.[11] Its binary companion, 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,[12] and perform one orbit around their centre of mass once every 3,200 years.
Naming
It was a member of indigenous Arabic asterismal-Nasaq al-Yamānī, "the Southern Line" of al-Nasaqān "the Two Lines",[13] 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).[14]
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)[15]
^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. ISBN1-931559-44-9.