Kap-2

Its story

Kappa-2 Boötis carries the traditional name Asellus Tertius —«the third donkey colt»— and pairs with Kappa-1 as a double visible in a small telescope, separated by 13.5 arcseconds. It is an A8 subgiant pulsing as a Delta Scuti variable: its brightness flickers gently every 1.08 hours as it nears the end of its main-sequence life with a nearly exhausted hydrogen core. At 162 light-years, it beats quietly across the cloak of the Herdsman.