Theta Cephei

Theta Cephei, Latinized from θ Cephei, is a stellar class A7, fourth-magnitude star in the constellation Cepheus. This displays at a metallic-line Am star. It is a white-hued, single-lined spectroscopic binary system, located about 127 light-years from Earth. The pair have an orbital period of 914.3 days; the eccentricity was long thought to be low, at 0.03, but recent calculations have put it at a much higher 0.377. They are separated by $914.3 d$. The companion star is calculated to be about 400 times fainter than the primary. It is completely invisible in the spectrum, but is estimated to be a K7 main sequence star.

Shared with η Cep, this star system has the title Al Kidr. In Chinese, 天鈎 (Tiān Gōu), meaning Celestial Hook, refers to an asterism consisting of 4 Cephei, HD 194298, η Cephei, α Cephei, ξ Cephei, 26 Cephei, ι Cephei and ο Cephei. Consequently, the Chinese name for θ Cephei itself is 天鈎三 (Tiān Gōu sān, the Third Star of Celestial Hook.).