SLAC Scientists Uncover Secrets of World’s Oldest Star Map

At the SLAC National Accelerator Laboratory in Menlo Park, California, researchers are employing advanced X-ray technology to investigate ancient parchment from a medieval monastery. Their goal is to reveal hidden details of what is believed to be the world’s oldest star map, originally created over 2,100 years ago by the renowned Greek astronomer Hipparchus. This historic catalogue is thought to have detailed more than 800 stars, including their brightness and positions, although the original document has yet to be discovered.

The parchment, which dates back to the sixth century, was found at St. Catherine’s Monastery in the Sinai Desert, where it had been overwritten with Christian texts. The initial discovery of its astronomical content occurred in 2012 when an undergraduate student at the University of Cambridge identified faint traces of Greek inscriptions related to astronomy in the manuscript known as the Codex Climaci Rescriptus.

X-ray Technology Reveals Ancient Texts

On January 21, 2026, lead researcher Victor Gysembergh of the French National Centre for Scientific Research expressed enthusiasm as the X-ray beam illuminated the parchment. “We just have line after line of text showing up, in ancient Greek from the astronomical manuscript,” he noted. The research team is hopeful that they will be able to identify the first star coordinates, which could significantly advance our understanding of early astronomical practices.

The X-ray analysis utilizes beams from SLAC’s synchrotron particle accelerator, the premier high-energy X-ray facility in the western United States. The team is investigating 22 pages of parchment that are approximately the size of standard hardcover book pages. Each page is inscribed with visible black and faded-brown ink from the monks, while remnants of the star map appear as faint smudges.

Researcher Minhal Gardezi from the University of Wisconsin explained that the X-ray technology can rapidly identify chemical traces from erased ink, allowing the team to differentiate between the monks’ later writings and those of Hipparchus. The original star map is believed to have been inscribed using ink derived from tannin-rich oak galls, a common resource in ancient times.

Significance of Hipparchus’ Work

Hipparchus, who lived in the second century B.C., is often regarded as a foundational figure in astronomy. His work laid the groundwork for future astronomers, including Ptolemy, who referenced Hipparchus’s findings in their own research. The connection to this ancient star map is further supported by historical references, solidifying its importance in the study of celestial navigation.

The research team has already begun to see results, with Gysembergh reporting the emergence of the word for the constellation Aquarius during the scanning process. “It could be a section where the manuscript is counting how many stars there are in a constellation,” he remarked. This discovery exemplifies the potential of the project to yield significant insights into how ancient civilizations understood the cosmos.

As the SLAC team continues its work, they are not only contributing to the field of astronomy but also advancing methods for analyzing historical documents. The facility has previously applied similar X-ray techniques to other ancient texts, including the Gutenberg Bible and Confucian manuscripts, exploring the origins of early printing technology.

The ongoing investigation into Hipparchus’s star map has the potential to reshape our understanding of astronomical history. As researchers decode the ancient texts, they hope to uncover valuable information about the early practices of astronomy and the cultural significance of celestial observation in ancient societies.