Kappa Boötis

Kappa Boötis is a double star in the constellation Boötes. Its name is a Bayer designation that is Latinized from κ Boötis, and abbreviated Kappa Boo or κ Boo. This star has the traditional name Asellus Tertius, which is pronounced and is Latin for "third donkey colt". The components have an angular separation of 13.5 arcsec; viewable in a small telescope. Kappa Boötis is approximately from Earth.

Properties

κ¹ Boötis is itself a double-lined spectroscopic binary star system. The primary component is an F-type main-sequence star star of class F2V, while the secondary is half the mass and much fainter.
κ² Boötis is classified as a Delta Scuti type variable star with a period of 1.08 hours Its brightness varies from magnitude +4.50 to +4.58. It is a slightly evolved A8 subgiant, which indicates the hydrogen at its core is all but exhausted. This star has more than double the mass of the Sun and nearly three times its girth. It has a high rate of spin, showing a projected rotational velocity of 128 km/s. The star is radiating 28 times the luminosity of the Sun from its photosphere at an effective temperature of 7,760 K.
A 17th-magnitude star nearly two arc-minutes away has been identified as a member of the multiple system with an estimated orbital period of 177,000 years. It is itself a close binary system consisting of two similar low-mass stars in a 234-year orbit.

Nomenclature

κ² Boötis, the brighter star of the pair, is also designated HD 124675, while κ¹ Boötis is HD 124674. The two stars share the Flamsteed designation 17 Boötis, but they have separate entries in the Hipparcos catalogue: HIP 69483 and HIP 69481 respectively.
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 κ Boötis, ι Boötis and θ Boötis. Consequently, the Chinese name for κ Boötis itself is 天槍一