Zi Wei Star as the name aptly suggests is used as an axiom for the study of Zi Wei Dou Shu. There had been alot of speculations on the identities of the Zi Wei Star. I insist on Thuban (α Draconis) as the original Zi Wei whereas in modern times, many people had insisted on Polaris. Here, we will investigate both historical records and also astronomical sciences.Every asterisms in Chinese astrology had all been referenced to mythological entities, especially during the Tang Dynasty, a period where there seemed to be many syncretism between Buddhistic and Taoist belief systems.
From the stars within the three enclosures closest to the celestial poles, to the 28 mansions, all had some personality. There are three entities that we will be particularly interested in to research on, namely: 1. 太极天皇大帝 (Tai Ji Tian Huang Da Di) from the Gou Chen (勾陈) area, 2. 北极紫微大帝 (Bei Ji Zi Wei Da Di) from the Bei Ji (北極) cluster, and 3. 天乙/太乙 (Tian Yi and Tai Yi) of Zi Wei You Heng (紫微右垣). From the above mythical figures, you might have figured out that Bei Ji Zi Wei Dai Di (also known as North Pole Zi Wei Emperor) may have some relevance to Zi Wei, and you are probably correct. This is the correct name given to this star. The Bei Ji cluster means North Pole in Chinese and consists of β Ursae Minoris, γ Ursae Minoris, 5 Ursae Minoris, 4 Ursae Minoris and Σ 1694. Consequently, β Ursae Minoris itself is known as 北極二 ( the Second Star of North Pole.), representing 帝 (Di), meaning Emperor, hence Zi Wei (紫微). Henceforth are we quick to assume that β Ursae Minoris also known as Kochab as the Zi Wei Pole Star? Yes and no, but we will get to that later.
Tai Ji Tian Huang Da Di, also known as the Supreme Heavenly Emperor sits in the Gou Chen area, and astronomically it really is Polaris at α Ursae Minoris. However do you notice that there is no direct reference to the star as that of Zi Wei? Perhaps it might be interesting for you to note that while Polaris is our axis mundi in current time, Kochab was at a slightly close proximity to the original celestial pole (although not near enough to be a pole star) back in Tang Dynasty which happens to fall between the classical period between 1500 BC- 500 AD). The Chinese back then might have regarded Kochab as Zi Wei, but many cultures of antiquity including the Chinese people did not really consider Kochab as the true pole star. What about Tian Yi (Celestial Great One) and Tai Yi (Primordial Great One) at Zi Wei You Heng (Zi Wei Right Enclosure)? These two entities are found at the 右樞 (You Shu; Right Pivot) known as Thuban (α Draconis) on constellation Draco. It is not referenced as Zi Wei. From the look of it, I should not be staking my claim that Zi Wei lies in Thuban, and that I should have said that the true Zi Wei lies in Kochab instead. However I am sticking on to my claim.
One thing that you might need to observe is that the axial precession of the Earth had given rise to different pole stars since times of antiquity. In 3000 BC, Thuban was indeed used as the celestial pole as a reference in many ancient cultures until 1900 BC. Subsequently there was no pole stars used as the axis mundi (not even Kochab) up until about 1500 AD whereby Polaris was used as a reference. We should look at another piece of evidence from also the Tang Dynasty: The Dunhuang Star Map. There is indication of Tian Huang (天皇) and North Pole/Bei Ji (北極) in the star map, but the interesting thing is that Zi Wei (紫微) actually lies somewhere.. not anywhere at North Pole/Bei Ji, not even in Thuban (α Draconis) but at Al Dhibain (η Draconis)! Now the thing is η Draconis was never a pole star. This goes to show that the ancient astronomers/astrologers possibly had some idea that Zi Wei is right over at the Draco constellation but missing about a little distance away from the actual Thuban, and that it does not really sit at Kochab. However the Zi Wei on the Dunhuang Star Map totally contradicts that of the mythological location of Bei Ji Zi Wei Da Di.
Let’s check if these are clear: 1. Zi Wei star is referred to as the axis mundi, the Pole Star used for circumpolar observations in astrology in all Chinese metaphysical texts, 2. Pole Star during times of antiquity had traditionally always been Thuban. 3. Polaris may be the new Pole Star, but it has nothing to do with being the Zi Wei star as evinced by examples above. 4. Zi Wei star location is not fixed in historical records, and many times they do not pertain to the exact location of the Pole Star, which contradicts point 1. If we go by the assumption that point 4 is subjected to some historical errors and since it is contradictory, the historical evidences are not valid, by the only inference I see the linkage between Point 1 and 2 and backed by Point 3, is that the true Zi Wei lies at Thuban.