20♉52 to 25♉26
The eighteenth Chinese lunar mansion is named 昴宿 Mǎo Su, “Hairy Head Mansion.” It is the fourth of the seven mansions of the White Tiger of the West.
The fourth asterism of the Hairy Head Mansion is called 天陰 Tiānyīn, “Yin Force.” It represents the yin energy in the sky, the dark area on the north side of the mountain, or the officials who hunt with the emperor. It is composed of five stars of the Aries constellation. [1]
| 2000 | 2050 | IAU | Chinese | Orb |
| 23♉24 | 24♉06 | τ¹ Ari | Tianyin Yi (1) | 1°00′ |
| 21♉57 | 22♉39 | ζ Ari, Al Butain IV | Tianyin Er (2) | 1°00′ |
| 23♉29 | 24♉21 | τ² Ari | Tianyin San (3) | 1°00′ |
| 20♉52 | 21♉34 | δ Ari, Botein | Tianyin Si (4) | 1°10′ |
| 25♉26 | 26♉08 | 66 Ari | Tianyin Wu (5) | 1°00′ |
Constellation Tianyin, the Yin Force
20♉52 to 25♉26
The five stars of the Yin Star are west of the Pleiades, signifying ministers who accompany the emperor on hunts and participate in conspiracies. If they are not clear, secrets will be leaked. [2]
The five stars of Tianyin govern the ministers who accompany the emperor on hunts. If they are not bright, it is auspicious; if they are bright, it signifies the leakage of forbidden words. [3]
The meaning of the name Celestial Yin Force is unclear, but it can be literally interpreted as the yin force which is retractive, passive, contractive and receptive in nature.