Delta Serpentis

Delta Serpentis (δ Serpentis, δ Ser) is a star system in the constellation Serpens, in its head (Serpens Caput).

It is approximately 210 light years from Earth. The light from the four stars in the system give a combined apparent magnitude of +3.80.

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.

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)