Thuban is a white star in Draco that was the pole star when the Egyptian pyramids were built, before the slow wobble of Earth’s axis moved the pole away.
At a glance
| type | white star (class A) |
|---|---|
| distance from the Sun | 303 light-years (92.9 pc) |
| its light left it | 303 years ago |
| luminosity | 324 × the Sun |
| radius | 6.38 × the Sun |
| surface temperature | 9,700 K |
| constellation | Draco (Dragon) |
Read off the piece’s own catalogue, the same values it draws with.
About Thuban
Thuban is a white star of class A, wider than the Sun and far more luminous. It is a spectroscopic binary, with a companion revealed by the shifting lines in its spectrum.
Earth’s axis wobbles slowly like a spinning top, a motion called precession, so the point in the sky it aims at traces a great circle over an immense span of time. In the time of the Old Kingdom of Egypt that point lay near Thuban; it has since moved towards Polaris, and Thuban will one day be near the pole again.
Its name comes from the Arabic for snake or dragon. Despite its letter alpha it is not the brightest star of Draco; Eltanin, in the dragon’s head, outshines it.
What you see in the piece
In the piece Thuban is a modest white point in the tail of Draco, far fainter than it would need to be to stand out. Fly out and it parts from the dragon’s other stars, which lie at many different distances.
Questions
Was Thuban the pole star?
Yes. Because of the slow precession of Earth’s axis, Thuban lay close to the north celestial pole when the Egyptian pyramids were built.