Tianjin

Authors: Lyu Haocheng

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Tianjin in Stellarium, across the Milky Way

Tiān Jīn (天津, Celestial Ford or Celestial Ferry), a Chinese constellation consists of 9 stars, located in Cygnus. This constellation is regarded as the "ferry or bridge of the Milky Way in the sky" because it spans across the Milky Way.

Concordance, Etymology, History

The imagery of a celestial ferry had already taken root in the Chinese imagination more than two millennia ago. The great poet Qu Yuan (c. 340–278 BCE) of the Warring States period—often called China's first romantic poet—wrote in his masterpiece Li Sao ("On Encountering Sorrow"):

At dawn I set forth from the Celestial Ferry (Tianjin); By dusk I had reached the westernmost horizon.

This magnificent line describes the poet's spiritual journey through the heavens, unbounded by earthly limits. Though Qu Yuan was not necessarily referring to the specific constellation later codified as Tianjin, his verse reveals that the image of a "Ferry of the Milky Way" had already entered the Chinese literary imagination in very ancient times. The earliest recorded description of what would later become the Tianjin constellation appears in Sima Qian's (c. 145–86 BCE) Records of the Grand Historian (Shiji). In the "Treatise on Celestial Offices," Sima Qian wrote:

Beside Wangliang (王良), there are eight stars cutting across the Milky Way, called Tianhuang ("Celestial Pier"). Beside Tianhuang is the River Star (Jiangxing). When the River Star stirs, men wade across the waters.

According to scholars of later eras, Tianhuang (another name for Tianjin) and the River Star together comprised the nine stars of the future Tianjin constellation. The River Star is Deneb, the brightest of the nine, while the other eight constitute the "pier." The omen that "men wade across the waters" would later inspire another constellation, Ren (Humans), consisting of five stars placed adjacent to Tianjin. (There is also another Chinese constellation named Tianhuang, consisting of five stars in the constellation Auriga, which should not be confused with the Tianhuang associated with Tianjin.) After Chen Zhuo (active 3rd century CE) unified the Chinese constellation system, the name of Tianjin was fixed. The Book of Jin (Jinshu, 晋书) states in its "Treatise on Astronomy":

Tianjin consists of nine stars lying across the Milky Way. It is also called Tianhan (a name of the Milky Way) or Tianjiang (Celestial River). It presides over the ferries and bridges of the Four Great Rivers (the Yangtze, Yellow, Huai, and Ji, refers to all rivers in general), thereby enabling the gods to traverse the four directions. If one star is missing, the fords and passes are blocked.

Tianjin and the Legend of the Cowherd and Weaver Girl

Weaving Girl (Zhinü), Cowherd(Niulang) and the Celestial Ford (Tianjin)

For those less concerned with the formal constellation, Tianjin lives on in a more beloved story—the legend of the Cowherd and the Weaver Girl.

The Weaver Girl (Zhinü) was a celestial maiden who wove the clouds and rosy dawns. The Cowherd (Niulang) was a handsome mortal who fell in love with her. They married and had two children, but the Queen Mother of the West was furious. She scratched a great river across the sky—the Milky Way—to separate them forever. The lovers could only weep across the celestial river once a year, on the seventh night of the seventh lunar month, when a flock of magpies would form a bridge with their wings, allowing them to meet for one fleeting embrace.

In many folk traditions, the bridge of magpies is none other than the Tianjin constellation itself. The nine stars of Tianjin stretch across the Milky Way exactly where the magpies are said to alight. Every summer, stargazers can see the "Summer Triangle"—Deneb (one star of Tianjin), Vega (the Weaver Girl), and Altair (the Cowherd)—forming a vast triangle in the eastern sky, the stars of the lovers and their bridge.

Tianjin in Geography

The Tianjin constellation was so well known that its name was later applied to several places on Earth. In traditional Chinese thought, there was a long‑held principle of xiang tian fa di (“modeling the earthly upon the heavenly”), whereby human constructions were deliberately designed to mirror celestial patterns.

Tianjin Bridge (Luoyang)

The clearest example is the Tianjin Bridge built across the Luo River in Luoyang during the Sui dynasty (605 CE). Following xiang tian fa di, the Luo River was conceived as the earthly counterpart of the Milky Way (Tianhan), and the bridge that spanned it was accordingly named after the "Celestial Ford" constellation. The bridge was part of a larger celestial allegory in the Sui‑Tang eastern capital, where seven key structures (including Heavenly Tower and Heavenly Street) mirrored the Sun, Moon, and five visible planets. Its stone pier foundations have been excavated in modern times.

Tianjin Municipality

The modern city of Tianjin also owes its name to this constellation. According to the History of Jin (Jinshi, 金史), a Tianjin River (天津河) already existed by 1206 CE. It was named after the constellation, taking its meaning from the phrase "a bridge across the Milky Way, a thoroughfare serving all waterways" (Tianhan Jinliang, Tongcao Zhongji, 天汉津梁、通漕众济), which explicitly draws on the celestial concept. The Tianjin River was designated as a section of the Grand Canal, serving as a key channel for grain transportation. Around the same time, another waterway, the Tongji River (通济渠), was also named based on the same phrase. The two rivers were placed under the unified management of a single patrol officer, known as the Tianjin River Patrol Officer.

A later, widely known tradition dates to the Ming dynasty. In 1400, Zhu Di, the Prince of Yan, boarded ships at the Tianjin River near what is now the Jinhua Bridge on the South Canal during the Jingnan Campaign against his nephew, the Jianwen Emperor. From this point, he switched from overland to waterborne advance and sailed south along the Grand Canal. After seizing the throne and ascending as the Yongle Emperor, he reportedly renamed the settlement Tianjin, meaning the "Ford of the Son of Heaven (Emperor)" (Tianzi Jindu, 天子津渡), in commemoration of his departure point. In 1404, he formally established the Tianjin Guard, which is traditionally regarded as the founding date of the city.

Beyond Earth

In 2019, the International Astronomical Union named a lunar crater at the Chang'e‑4 landing site "Tianjin". Together with neighboring craters Zhinü (Weaver Girl) and Hegu (Cowherd), it recreates the Summer Triangle on the lunar surface – with Tianjin again representing the celestial bridge.

Identification of stars

Tianjin Star is quite prominent in the sky, corresponding to the 9 stars in the constellation Cygnus, without controversy.

Star Names or Orders(Qing)	Ho PENG YOKE	Yi Shitong Based on catalogue in 18th century	Pan Nai based on Xinyixiangfayao Star Map	Pan Nai based on catalogues in Yuan dynasty	SUN X. & J. Kistemaker Han Dynasty	Boshun Yang before Tang dynasty	Boshun Yang Song Jingyou(1034)
1st	γ Cyg	γ Cyg	γ Cyg	γ Cyg	γ Cyg	γ Cyg	γ Cyg
2nd (Determinative)	δ Cyg	δ Cyg	δ Cyg	δ Cyg	δ Cyg	δ Cyg	δ Cyg
3rd	ο1 Cyg	30 Cyg	ο1 Cyg	ο1 Cyg	ο1 Cyg	ο1 Cyg	ο1 Cyg
4th	α Cyg	α Cyg	α Cyg	α Cyg	α Cyg	α Cyg	α Cyg
5th	ν Cyg	ν Cyg	ν Cyg	ν Cyg	ν Cyg	ν Cyg	ν Cyg
6th	τ Cyg	τ Cyg	τ Cyg	τ Cyg	τ Cyg	τ Cyg	τ Cyg
7th	υ Cyg	υ Cyg	υ Cyg	υ Cyg	υ Cyg	υ Cyg	υ Cyg
8th	ζ Cyg	ζ Cyg	ζ Cyg	ζ Cyg	ζ Cyg	ζ Cyg	ζ Cyg
9th	ε Cyg	ε Cyg	ε Cyg	ε Cyg	ε Cyg	ε Cyg	ε Cyg

Maps (Gallery)

• Tianjin
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  Tianjin on Cheonsang Yeolcha Bunyajido
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  Tianjin on Suzhou Star Map
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  Tianjin on Yixiang Kaocheng star map (18th century)

IAU Working Group on Star Names

In 202x, the name of the historical constellation "xxx" was suggested to be used for one of the stars in this constellation. ...

Decision: ...

References

References (Chinese)