Leidian (雷電)
Authors: Boshun YANG, Susanne M Hoffmann
Léi Diàn (Thunder and Lightning, 雷電) is a six-star Chinese asterism belonging to the outer asterisms of the Gan school. It lies south of Yingshi. Although modern reconstructions of its membership and outline vary, all major identifications place it in the present-day constellation Pegasus. This asterism might have been created in late Western Han. Its primary image is thunder and lightning. In the same sector of the sky, it forms a meteorological cluster with Pīlì (Thunderclap) and Yúnyǔ (Cloud and Rain).
Since August 2026, Leidian is also a modern IAU-star name; it refers to the star ρ Peg in Pegasus.
Concordance, Etymology, History
The two elements of the name already distinguished sound from light in early lexical thought. The Shuowen jiezi 說文解字explains the archaic graph 靁 as the movement caused when yin and yang press against one another, with 畾 evoking a revolving form; it defines 電 as the flash produced by the excitation of yin and yang. The Eastern Han Shiming釋名 gives phonetic glosses: thunder (léi) resembles the rumble of objects turning against an obstruction, while lightning (diàn) is so called because it vanishes as soon as it appears. These are not modern meteorology, but they show a clear conceptual pairing of two related yet distinct phenomena.
Because thunder is invisible, it was rendered through the tangible technology of the drum. In the Eastern Han Lunheng論衡, Wang Chong王充 reports that painters represented thunder as a string of connected drums and portrayed Leigong, the Thunder Lord, as a strongman pulling the drums with one hand and striking them with a mallet in the other. Wang’s purpose was to refute a literal divine-drum explanation, but his criticism preserves evidence for a visual convention: by the Eastern Han, the Thunder Lord, linked drums, and the striking mallet formed a recognizable image. The asterism thus stood between two modes of knowledge—natural interaction between yin and yang, and a materialized image of drums, divinity, and heavenly authority.
Identification of stars
Leidian underwent a substantial change in membership. Yang Boshun dates the major alteration to the Huangyou period (1049-1054 CE) of the Northern Song and distinguishes an early to Jingyou pattern from the Huangyou pattern; Yi Shitong’s Qing numbering represents another catalogue tradition influenced by European astronomy.
| Star Names or Orders(Qing) | Han Dynasty (SUN X. & J. Kistemaker[1]) | 3rd to 6th Century (Boshun Yang[2]) | Song Dynaty (Boshun Yang[2], 1034 CE) | Song Dynasty (Pan Nai[3], 1052 CE) | Song Dynasty (Boshun Yang[2], 1052 CE) | Qing Dynaty (Yi Shitong[4], 18th Century) |
|---|---|---|---|---|---|---|
| 1st | σ Peg
（determinative） |
σ Peg
（determinative） |
σ Peg
（determinative） |
σ Peg
（determinative） |
σ Peg | ζ Peg
(42 Peg) |
| 2nd | ρ Peg | HIP 113445 | HIP 113445 | 52 Peg | ρ Peg
（determinative） |
ξ Peg
(46 Peg) |
| 3rd | 55 Peg | ρ Peg
(50 Peg) |
ρ Peg
(50 Peg) |
55 Peg | 59 Peg | σ Peg
(49 Peg) |
| 4th | 58 Peg | 55 Peg | 55 Peg | 58 Peg | 58 Peg | 55 Peg |
| 5th | 66 Peg | 58 Peg | 58 Peg | 66 Peg | 66 Peg | 66 Peg |
| 6th | 70 Peg | 57 Peg | 57 Peg | 77 Peg | 70 Peg | 70 Peg |
Maps (Gallery)
The configurations of Leidian depicted in the three early star maps share a common pattern, whereas the Suzhou star map, engraved in the thirteenth century during the Song dynasty, begins to show noticeable changes.
When European Jesuits in the late Ming dynasty (1630s) reidentified this asterism on the basis of European star catalogues, they not only assigned different constituent stars to it but also failed to reconstruct it in full, leaving three stars unaccounted for. Jesuits in the Qing dynasty restored the asterism to its full complement, although their identification of its stars had already diverged from the traditional one.
Moreover, although the star maps in the Xin Yixiang Fayao used by Pan Nai ultimately derive from the Song dynasty, they actually belong to a revised Qing-dynasty edition and therefore display a high degree of similarity to eighteenth-century versions.
| historical map | modern identification | same in Stellarium |
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IAU Working Group on Star Names
In 2026, the name of the historical constellation "Leidian" was suggested to be used for ρ Peg in this constellation, for it is relatively brighter and was determinative star.
Decision: ...
References
- ↑ Sun Xiaochun. & Kistemaker J. The Chinese sky during the Han. Leiden: Brill. 1997, Pp241-6.
- ↑ 2.0 2.1 2.2 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).
- ↑ Pan Nai潘鼐. Zhongguo Hengxing Guance shi中国恒星观测史[M]. Shanghai: Xuelin Pree. 1989.
- ↑ Yi Shitong伊世同. Zhongxi Duizhao Hengxing Tubiao中西对照恒星图表1950. Beijing: Science Press.1981.
