New Research These Scientists Say They’ve Identified the Oldest Known Star Chart in the World A new preprint suggests that an ancient Chinese star catalog dates to 355 B.C.E. But other researchers aren’t convinced, arguing that the original coordinates are misaligned by one degree An ancient star map (not the document analyzed in the new research) unearthed in Dunhuang, China, in the seventh century C.E. Public domain via Wikimedia Commons Thousands of years ago, Chinese astronomers studied the sky using an ancient record of constellations and their coordinates. Known as the “Star Manual of Master Shi,” the document is the oldest surviving star catalog in China. But now, scientists say the map dates to the fourth century B.C.E.—some 250 years earlier than previously thought. If their conclusion is correct, it would make the document the oldest known star chart in the world. Boliang He and Yongheng Zhao, both researchers at the National Astronomical Observatories in Beijing,Research in Astronomy and Astrophysics, the manual was created in 355 B.C.E. and modified in 125 C.E. That’s more than 200 years before the ancient Greek astronomer Hipparchus made his star catalog, which has long been considered the world’s oldest. The manual is attributed to Shi Shen, a famous court astronomer during China’s Warring States period. The new date falls around the period historians think Shi may have lived. “Our findings align perfectly with these historical accounts, vividly demonstrating the continuity and completeness of ancient Chinese historical records,” He tells Science’s Joshua Sokol. “These discoveries left us deeply surprised.” A 19th-century artist's portrait of Hipparchus, a Greek astronomer who made one of the world's oldest star maps Public domain via Wikimedia Commons Over thousands of years, Earth’s axis of rotation has slowly shifted, altering the locations of the celestial poles—the points in the sky around which scientists map stars. This slow change is called precession, and it forms the basis of Zhao and He’s research. Accounting for precession in an old star map should allow “modern researchers to precisely date when the catalog must have been created, much like counting rings in a tree trunk can reveal a tree’s age,” according to Science. Zhao and He used a type of A.I. known as computer vision to estimate the position of the celestial north pole at the time the star manual was made. They dated the map using that information. “I think this is pretty definitive,” David Pankenier, an emeritus scholar of Chinese astronomy at Lehigh University in Pennsylvania who wasn’t involved in the study, tells Live Science’s Joanna Thompson. Pankenier adds that the study also confirms previous research by the 20th-century British biochemist Joseph Needham, who specialized in ancient Chinese scientific development. But as Boshun Yang, a science historian at the University of Science and Technology of China, tells Science, “I hold a totally different perspective.” Yang studies the dating of ancient astronomical documents, and he thinks that many of Shi’s coordinates may be misaligned from the celestial north pole by roughly one degree. Previous research has shown that the star map dates to around 103 B.C.E. when taking this potential misalignment into consideration. The new study claims that the map was updated in 125 C.E. in order to account for measurements that appear to have been taken centuries apart. However, the one-degree misalignment theory also removes those discrepancies, as Daniel Morgan, a science historian at France’s Center for Research on East Asian Civilizations, tells Live Science. “It just so happens that if you take this really anodyne consideration into account—that maybe they built an instrument and it was not perfect—then the astronomers’ data analysis perfectly aligns with the human story,” Morgan says. Get the latest stories in your inbox every weekday.