Tianguan — Star in Taurus
HIP 26451; Zeta Tauri; 123 Tauri
About Tianguan
Description
Zeta Tauri is a blue star of spectral type B4IIIpe at magnitude 3.0 in Taurus. Located roughly 440 light-years from Earth, it marks the tip of the Bull's southern horn. The 'pe' in its spectral classification indicates it is a shell star — a rapidly rotating star surrounded by a disk of expelled gas. It is also a spectroscopic binary.
Observing Tips
Zeta Tau marks the southern horn tip of Taurus, forming a pair with Beta Tau (Elnath) at the northern horn tip. It is easy to find by following the line of Orion's Belt to the upper left (northwest). The Crab Nebula (M1) lies about 1 degree to the northwest of Zeta Tau, making this star the primary guide for finding one of the most famous deep-sky objects. Best observed from November through March.
History
Zeta Tauri has no widely used traditional proper name, though it has occasionally been called Tianguan in Chinese astronomy, meaning 'celestial gate.' Its proximity to the Crab Nebula (M1) is historically significant — the 1054 supernova that created the Crab Nebula was recorded very close to this star's position.
Fun Facts
Zeta Tau is the most important guide star for finding the Crab Nebula (M1). When Chinese astronomers recorded the 'guest star' of 1054, they described its position relative to Zeta Tau. As a shell star, Zeta Tau's equatorial disk causes its spectrum to show emission lines that vary over time as the disk changes.
Observe
1Physical Properties
2Position & Identifiers
3How easy to spot?
| Equipment | Bortle 3 | Bortle 4 | Bortle 5 |
|---|---|---|---|
| Naked eye Naked eye | Easy | Easy | Easy |
| 50 mm finder 50mm finder | Easy | Easy | Easy |
| 150 mm telescope 150mm scope | Easy | Easy | Easy |
Bortle 3 = rural · 4 = outer suburbs · 5 = suburbs
4Visibility
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5Survey Image
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Explore
7
Size Comparison
8
Compare Stars
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Spectral Classification
10
Hertzsprung-Russell Diagram
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Stellar Lifecycle
12
Blackbody Spectrum
13
Stellar Absorption Spectrum
Simulated absorption spectrum based on spectral type. Hover over lines to identify elements.
14
Stellar Fusion
Discover
15Stellar Notes
16
Light Travel Time Machine
17
Relativistic Travel
Nearby in the Sky
Other targets within a few degrees — pan your scope a little and keep exploring.
Visibility scores assume a 150 mm Newton at Bortle 4.
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