Iota Boötis


Iota Boötis is a star system in the constellation Boötes. It has the traditional name Asellus Secundus and the Flamsteed designation 21 Boötis. It is approximately 95 light years from Earth.

Nomenclature

This star, along with the other Aselli and λ Boo, were Aulād al Dhiʼbah, "the Whelps of the Hyenas".
In Chinese, 天槍, meaning Celestial Spear, refers to an asterism consisting of ι Boötis, κ2 Boötis and θ Boötis. Consequently,the Chinese name for ι Boötis itself is 天槍二

Components

Iota Boötis has a companion at an angular distance of 38.6 arcseconds, easily separated with binoculars.
The primary component is a white A-type main sequence dwarf with a mean apparent magnitude of +4.75. It is classified as a Delta Scuti type variable star and its brightness varies from magnitude +4.73 to +4.78 with a stable period of 38 minutes.
The companion, HD 234121, is a magnitude +8.27 main sequence star belonging to spectral class K0. It is separated from ι Boo by 1,100 AU.
The Washington Double Star Catalog lists a third component, a 14th magnitude star at 90 arc seconds.