Tiangang (天綱)
Tiangang
Authors: Lyu Haocheng
| Asterism Info | |
| Native | 天綱 |
|---|---|
| Romanisation | Tiān Gāng |
| IPA | /tʰjɛn˥.kɑŋ˥/ |
| Translation | Celestial Rope |
| Position (2000) | |
| Right ascension | 22h 31m 30.89s |
| Declination | −32° 20′ 36.0″ |
| Area | 0 sq. deg. |
| Stars | |
| Bright stars | 1 |
| Bayer/Flamsteed stars | 1 |
| Stars brighter than 3.00m | 0 |
| Brightest star | β Psc (4.29m) |
| Taxonomy | |
| category of asterism | constellation |
| IAU- constellations | PsA |
Tiān Gāng (天綱, Celestial Rope) is a traditional Chinese asterism belonging to the Shi (室) mansion, the sixth of the seven mansions of the Black Tortoise of the North in the Twenty-Eight Mansions system. Among the Three Schools of ancient Chinese astronomy, it is classified as a Wu Xian asterism. The asterism consists of a single star located southwest of Běiluò Shīmén (北落師門, α Piscis Austrini). In modern constellation boundaries, Tiangang lies within Piscis Austrinus (the Southern Fish). The name "Tiān Gāng" literally means "Celestial Rope" — a reference to the large ropes used to pitch tents — and symbolically represents the Celestial Military Tent of the emperor on campaign.
Concordance, Etymology, History
The Chinese character 綱 (gāng) originally means a rope — specifically the main rope of a net. Tiangang thus means "the celestial rope." Wu Xian (巫咸) states: "Tiangang is a great rope; it is used to set up tents, as required when the Son of Heaven goes on tours, bestows rewards, and encamps in the field." Tiangang thus came to symbolize the military tent of the emperor.
This interpretation is echoed in Li Bo's Tianwen Daxiang Fu (天文大象賦 / Rhapsody on the Great Images of the Celestial Sphere), which describes: "The Celestial Money accumulates like a mountain of tribute; the Celestial Rope provides rest and a field banquet." Here, Tiangang is depicted as the emperor’s resting place and banquet site during military campaigns.
The Book of Jin (Jinshu, 晋书) states in its "Treatise on Astronomy": "One star southwest of Beiluo Shimen is called Tiangang; it governs the military tent." The History of Song, Treatise on Astronomy (Songshi · Tianwen Zhi, 宋史·天文志) adds: "Tiangang, one star, southwest of Beiluo Shimen — it governs the military tent and palace lodges, where the Son of Heaven gathers for hunting expeditions."
Tiangang is located adjacent to Beiluo Shimen (北落師門) — the gate of the northern military camp; Tiangang is the emperor’s tent within that camp — the command post where the emperor presides when personally leading a campaign. Together with the surrounding asterisms — Lěibìzhèn (壘壁陣, Line of Ramparts), Yǔlínjūn (羽林軍, Palace Guard) — they form a complete celestial military encampment.
Identification of stars
The identification of Tiangang has shifted over time. The early Tiangang star was likely γ PsA. The Tongzhan Daxiangli Xingjing (通占大象曆星經) records Tiangang as two stars, although the star numbers in this text are known to contain numerous errors. This alternative identification, however, appears only in this text; the mainstream tradition consistently records it as a single star. If accepted, they would correspond to γ and δ PsA.
During the Northern Song Huangyou reign (1052 CE), the observation of Tiangang was revised to β PsA, and this identification became fixed. The Yuan dynasty Tianwen Huichao (天文匯抄, 14th century) instead placed it at γ Gru, far from Beiluo Shimen; the late Ming Xianglin star map (象林, 17th century) followed a similar identification. However, most contemporary star charts continued to depict it beside Beiluo Shimen, indicating that the β PsA identification remained a mainstream tradition.
In the late Ming, the Jesuit-led official star catalogue deleted Tiangang altogether. It was restored in the 18th-century Qing catalogue Yixiang Kaocheng (儀象考成), but reassigned to δ PsA.
| Star Names or Orders(Qing) | Han Dynasty
(SUN X. & J. Kistemaker[1]) |
before Tang dynasty: 3rd to 6th Century
(Boshun Yang[2]) |
Song Dynaty: Huangyou, 1052
(Pan Nai[3], based on Xinyixiangfayao Star Map) |
Yuan dynasty: 1279-1368
(Pan Nai[4]) |
Qing dynasty: 18th Century
(Yi Shitong[5]) |
Ho PENG YOKE[6] |
|---|---|---|---|---|---|---|
| Tiangang | β PsA | γ Psc | β Psc | γ Gru | δ PsA | δ PsA |
Maps (Gallery)
IAU Working Group on Star Names
In 2026, the name "Tiangang" was proposed for β PsA in this constellation, as β PsA represents the later identification of the star.
Decision: ...
References
- ↑ Sun Xiaochun. & Kistemaker J. The Chinese sky during the Han. Leiden: Brill. 1997, Pp241-6.
- ↑ B.-S. Yang杨伯顺, Zhongguo Chuantong Hengxing Guance Jingdu ji Xingguan Yanbian Yanjiu 中国传统恒星观测精度及星官演变研究 (A Research on the Accuracy of Chinese Traditional Star Observation and the Evolution of Constellations), PhD thesis, (Hefei: University of Science and Technology of China, 2023). 235-296.
- ↑ Pan Nai潘鼐. Zhongguo Hengxing Guance shi中国恒星观测史[M]. Shanghai: Xuelin Pree. 1989. Fig 55.
- ↑ Pan Nai潘鼐. Zhongguo Hengxing Guance shi中国恒星观测史[M]. Shanghai: Xuelin Pree. 2009. p435-443.
- ↑ Yi Shitong伊世同. Zhongxi Duizhao Hengxing Tubiao中西对照恒星图表1950. Beijing: Science Press.1981.
- ↑ P.-Y. Ho, “Ancient And Mediaeval Observations of Comets and Novae in Chinese Sources,” Vistas in Astronomy, 5(1962), 127-225.
