Delta Boötis
Double star in the northern constellation Boötes
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Nomenclature
Delta Boötis is a Bayer designation that is Latinized from δ Boötis, and abbreviated Delta Boo or δ Boo. This star is sometimes called Princeps , meaning prince or prime in Latin. The origin of this name is unclear, although it usually appears in an astrological context.
In Chinese astronomy, 七公 (Qī Gōng), meaning Seven Excellencies, refers to an asterism consisting of δ Boötis, 42 Herculis, τ Herculis, φ Herculis, χ Herculis, ν1 Boötis and μ1 Boötis. Consequently, the Chinese name for δ Boötis itself is 七公七 (Qī Gōng qī, English: the Seventh Star of Seven Excellencies). R. H. Allen's Star Names (1899) referred to this asterism as Tseih Kung, "the Seven Princes". The IAU Working Group on Star Names approved the name Qigong for Delta Boötis A on 15 April 2026, after the Chinese constellation.
With β Boötis (Nekkar), γ Boötis (Seginus) and μ Boötis (Alkalurops), this star formed an asterism called in Arabic Al Dhi᾽bah, the female wolves or hyenas; similar names are found in Draco (see Zeta Draconis). Rhoads (1971) listed Thiba as a name for δ Boötis.
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Properties
This system consists of a pair of stars located in physical proximity to each other and sharing a similar motion through space, suggesting that they may form a binary star system. Based upon their angular separation and their distance, they have a projected separation of 3,800 astronomical units (AU). If they are gravitationally bound to each other, the orbital period of the system would be at least 120,000 years.
The brighter member of the pair has a stellar classification of G8 III, indicating that it has exhausted the supply of hydrogen at its core and evolved into a giant star. It now has a radius more than eleven times the radius of the Sun. Compared to the Sun, this star appears deficient in elements other than hydrogen and helium—what astronomers term the star's metallicity. The outer envelope of this star has an effective temperature of 4,810 K, which is what gives it the characteristic yellow hue of a G-type star.
The secondary component has a stellar classification of G0 V, which suggests it is a main-sequence star that may be similar in physical properties to the Sun. The apparent visual magnitude of this star is 7.81, making it much less luminous than the primary component.