Zeta Tauri
Zeta Tauri (ζ Tau, ζ Tauri, Shurnarkabti-sha-shūtū) is a binary star in the zodiac constellation Taurus, the Bull. It has an apparent visual magnitude of 3.0, which is bright enough to be seen with the naked eye. Parallax measurements place it at a distance of roughly 440 light-years from the Earth.
In Chinese astronomy, Zeta Tauri is called 天關, Pinyin: Tiānguān, meaning Celestial Gate, an asterism within the Net (畢宿 Bì Xiù) mansion (see also: Chinese constellation). 天關 (Tiānguān) has also been transliterated as Tien Kwan.
Technically, Tiānguān refers not just to Zeta Tauri but to an asterism of which Zeta Tauri is the main star, alongside
113 Tau,
126 Tau,
128 Tau,
129 Tau,
130 Tau and
127 Tau (see Taurus (Chinese astronomy)).
Properties
This is a single-lined spectroscopic binary system, which means the two components are orbiting so close to each other that they can not be resolved with a telescope. Instead, the orbital motion of the primary component is indicated by Doppler effect shifts in the absorption lines in its spectrum. The two components are separated by an estimated distance of about 1.17 Astronomical Units, or 117% of the distance from the Earth to the Sun. They are following circular orbits with a period of nearly 133 days.