Tiansi

Bronze chariot in Qin dynasty (220 BCE -206 BCE) with four hourses

Tiansi profile card of modern star name (CC BY Sadegh Faghanpour for IAU-WGSN).

Tiān Sì (Heavenly Quadriga, 天駟) comprises four of the five stars forming the constellation Wangliang (王良) and represents the four horses pulling the chariot. It may thus be regarded as a constituent sub-constellation/asterism of Wangliang (王良).

Concordance, Etymology, History

Given the intimate cultural association between Tiansi and Wangliang, the two must have been conceived simultaneously. In their earliest stage, however, they might be regarded as distinct constellations, as recorded in the Tianguan shu (Book of Heaven Officials, 天官書). Only later, in the Shishi xing jing (Shi’s Star Canon, 石氏星經) later , were they formally unified into a single constellation under the name Wang Liang. Nevertheless, even long after their amalgamation, tradition continued to recognize the leftmost four stars of Wangliang as the “Quadriga” and some star map explicitly marked them as Tian Si.

It should be noted that the lodge Fang (the fourth of the Twenty-Eight Lodges) also bore the alternate name Tian Si (“Heavenly Quadriga”), a designation that had already been in use at least as early as the late sixth century BCE—earlier than the historical figure of Wang Liang himself. The only difference lies in that Fang comprises four stars representing the quadriga, yet it lacks a corresponding charioteer such as Wang Liang.

Identification of stars

Star Names	Orders(Qing)	Ho PENG YOKE	Yi Shitong Based on catalogue in 18th century	Pan Nai based on Xinyixiangfayao Star Map and Huangyou Catalogue	SUN X. & J. Kistemaker Han Dynasty	Boshun Yang before Tang dynasty	Boshun Yang Song Jingyou(1034)
Wangliang (王良) (Determinative)	1st	beta Cas	beta Cas	beta Cas	beta Cas	beta Cas	beta Cas
Tiansi	2nd	kappa Cas	kappa Cas	gamma Cas	gamma Cas	gamma Cas	gamma Cas
	3rd	gamma Cas	eta Cas	eta Cas	eta Cas	eta Cas	eta Cas
	4th	eta Cas	alpha Cas	alpha Cas	alpha Cas	alpha Cas	alpha Cas
	5th	alpha Cas	lambda Cas	zeta Cas	zeta Cas	zeta Cas	zeta Cas

Maps (Gallery)

historical map	modern identification (Yang 2023)	same in Stellarium 24.4
Wangliang in Suzhou Star Map	Wangliang Reconstructed by Boshun Yang (2023) based on Huangyou Star Catalogue in 1052 CE	Wangliang before 17th Century in Stellarium
Wangliang in Jesuits Star Map in 17th Century	Wangliang Reconstructed by Yi Shitong (1981) based on Qing Star Catalogue in 18th Century	Wangliang after 17th Century in Stellarium

Tiansi stickfigure of modern star name (CC BY Sadegh Faghanpour for IAU-WGSN).

Star Name Discussion (IAU)

In 2025, the name of the historical constellation Tiān Sì (Heavenly Quadriga, 天駟) was proposed for a star in its region, with discussion focusing on γ Cassiopeiae.

On November 12, 2025 adopted the name Tiansi for γ Cas (27 Cas, HR 264, HD 5394, HIP 4427). γ Cas is a multiple system, and the name specifically refers to the massive primary star γ Cas Aa, which is a B0.5IVe star. The star is a famous eruptive variable, indeed the prototype of the γ Cas class, whose magnitude has varied historically between about magnitude 1.6 and 3.4. In recent years, the mean Johnson V magnitude has been around 2.17 (Smith & Henry 2021).

References

References (Chinese)