Magnitude 3.851 Apparent magnitude (V) 3.851 | Constellation Hercules | |
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People also search for Xi Herculis, Pi Herculis, Tau Herculis | ||
Theta Herculis (θ Her, θ Herculis) is a fourth-magnitude star in the constellation Hercules. It has the traditional name Rukbalgethi Genubi.
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Properties
Theta Her is a variable K-type giant star with stellar classification K1IIaCN. In 1935, French astronomer P. Muller identified Theta Herculis as an irregular variable with a range of magnitudes between 3.7 and 4.1 and a periodicity of roughly 8–9 days.
Etymology
In the Calendarium of Al Achsasi Al Mouakket, this star was designated Rekbet al Jathih al Aisr, which was translated into Latin as Genu Sinistrum Ingeniculi, meaning the left knee of the kneeling man. The traditional name Rukbalgethi Genubi that is encountered in various texts is etymologically similar to the stars Ruchbah and Zubenelgenubi, the term "ruchbah" meaning "knee" while "genubi" signifies "southern"—hence the "southern knee", a meaning which can be gleaned more easily by looking at the accompanying constellation map.
In Chinese, 天紀 (Tiān Jì), meaning Celestial Discipline, refers to an asterism consisting of θ Herculis, ξ Coronae Borealis, ζ Herculis, ε Herculis, 59 Herculis, 61 Herculis, 68 Herculis and HD 160054. Consequently, θ Herculis itself is known as 天紀九 (Tiān Jì jiǔ, English: the Ninth Star of Celestial Discipline.)