A new study has re-ignited academic debate over the origins of the world’s earliest star chart, placing an ancient Chinese manuscript—the Star Manual of Master Shi—at the forefront of world astronomical history. Using a cutting-edge artificial intelligence technique, researchers at the Chinese National Astronomical Observatories dated this manuscript to around 355 BCE, placing its origin over two centuries earlier than previously believed and making it the oldest star catalog ever discovered.

The Dunhuang map—distinct from the chart studied in the new research—is an early Chinese star map from the Tang Dynasty (CE 618–907). Public domain

The study, currently under review by Research in Astronomy and Astrophysics, applied the Generalized Hough Transform, a sophisticated computer vision method, to digital images of the manuscript. The method, widely used in image processing, allowed researchers to compare the positions of stars that were listed in the catalog with modern-day astronomical coordinates, accounting for distortions due to Earth’s axial precession and positional inaccuracies in ancient recordings.

Dating back as far as Shi Shen, the prominent Chinese astronomer of the Warring States period, the Star Manual of Master Shi (石氏星经) has long perplexed historians due to star position discrepancies that would appear to span centuries. This study, however, describes these inconsistencies not as errors of observation but as a series of periodic updates. Based on the study, the catalog originated in the 4th century BCE, with a comprehensive round of updates being made around CE 125—possibly during Zhang Heng’s tenure, the famous Eastern Han astronomer and inventor of the armillary sphere.

Zhang Heng, twice Grand Astrologer (Taishi Ling), oversaw systematic astronomical observations and conceivably incorporated new data into the catalog. As a result, the manuscript is a composite of two distinct eras—one 4th-century BCE and the other 2nd-century CE. This layered history, the researchers argue, explains the temporal spread of the star positions recorded in the chart.

Clay tablet with two columns of inscription. Astronomical treatise, tablet 1 of the series Mul-Apin (“the plough star”) which includes a list of the three divisions of the heavens, the dates (in the ideal 360-day year) of the rising of principal stars and of those which rise and set together, and the constellations in the path of the moon; nearly complete. Credit: British Museum, CC BY-SA 4.0

However, the findings have sparked mixed opinions in the scholarly world. Despite ongoing controversy, the significance of the discovery is widely accepted. The Chinese text pre-dates the Hipparchus Star Catalog (c. 130 BCE), which for a long time was considered the oldest structured celestial record in the Western tradition. While Babylonian sources as old as the 8th century BCE do describe star positions, they do not have the graphical mappings and organized layouts of the Star Manual of Master Shi, which contains more than 120 constellations and an arrangement of the night sky.

Aside from the science, this discovery has cultural significance. For many decades, ancient Chinese achievements in astronomy were downplayed by Western scholars. These new findings confirm China’s foundational contribution to humanity’s search for knowledge about the universe.

While debates about the details of dating persist, the Star Manual of Master Shi today is a testament to Chinese scientific achievement in the past. If confirmed, this chart predates its Greek and Babylonian counterparts both in form and layout.