Thuban (Arabic ثعبان, DMG tU ʿ bān, snake ') is the proper name of the star α Draconis ( Alpha Draconis ) in the constellation Draco. Thuban belongs to the spectral class A0 and has an apparent magnitude of 3.1 mag. Thuban is about 300 light-years away from Earth.
2800 BC served as a Thuban Polaris to determine the northern Himmelpols. Since the Earth's axis in space is not completely stable, but executes a slow precession ( precession ), slowly the situation of the celestial poles shifting. This can take over the function of the polar star in the course of time other stars. In this former special meaning of the star and the labeling Thubans returns as the main star (ie alpha) of the Dragon.