Tianguan (Zeta Tauri)
Tianguan (Zeta Tauri) is a star in the constellation Taurus, magnitude 3.0.
The Celestial Gate at the tip of the Bull’s horn — beside which a ‘guest star’ blazed in 1054.
In July 1054 Chinese astronomers recorded a ‘guest star’ near Tianguan, bright enough to be seen in daylight for 23 days. It was a star exploding as a supernova, and its wreckage is the Crab Nebula, M 1, a supernova remnant about a degree from Tianguan in our sky. Tiānguān itself means the Celestial Gate — a frontier gate within the Net, one of the Chinese lunar mansions.
Tianguan is a pair too close for any telescope to split, revealed only by the shifting lines in its spectrum. The main star is a giant of more than 11 solar masses, spinning fast and wrapped in a disc of gas thrown off from its equator — a Be star. A one-armed spiral wave runs through that disc, which may be wobbling under the pull of the companion. That companion has about the Sun’s mass and may be a white dwarf feeding on the gas, which would explain the hard X-rays the system gives off.
Tianguan (Zeta Tauri) is 440 light-years away: the light we see from it set off around 1585, 25 years before Galileo first turned a telescope to the sky.
Did you know?
- A year of 133 days. The two stars of Tianguan circle each other every 133 days on circular orbits, a little farther apart than Earth is from the Sun.
- Eclipses that vanished. Watching from Croatia’s Hvar Observatory in 1981–1986, astronomers saw what looked like eclipses. Later studies, including Hipparcos data, could not confirm them.
The blue-white 3rd-magnitude star at the tip of the Bull’s southern horn. The Crab Nebula, M 1, lies just over a degree to its north-west — this is the usual jumping-off point for finding it.
When and where to see it
It is best placed in the evening sky around January, when it crosses the meridian at about 10 pm local time (around midnight in December). It can be seen from everywhere north of 69°S and never sets north of 69°N.
At its highest it stands 61° up from 50°N, 76° up from 35°N, 69° up from the equator, 34° up from 35°S.
Facts
- Type
- Star
- Constellation
- Taurus
- Designations
- Zeta Tauri, ζ Tau, 123 Tau, HR 1910, HD 37202, HIP 26451
- Magnitude
- 3.0
- Position
- RA 5h 37.6m, Dec +21° 9′ (J2000)
- Spectral type
- B1IVe_shell
- Colour
- blue-white (B−V -0.19)
- Distance
- 440 light-years
- Discovered
- Known since antiquity
Open AstroPilot to see when Tianguan (Zeta Tauri) is highest tonight from your location, how easy it is with your telescope or binoculars, and an eyepiece view.