MENLO PARK, California, USA — An international team of researchers is working to restore what is believed to be the oldest surviving map of the night sky, hidden for centuries beneath religious texts in an ancient Syriac manuscript. Studies suggest the celestial chart may date back to the renowned Greek astronomer Hipparchus, who lived between 190 and 120 BC.
The manuscript, known as the Codex Climaci Rescriptus, is a rare example of a palimpsest — a manuscript in which older texts were scraped off and overwritten, often by medieval monks, due to the scarcity and cost of writing materials. In this case, a Syriac text was written over an older Greek layer containing precise astronomical data.
The modern story of this discovery began in 2022, when a detailed analysis of the sixth-century manuscript revealed that the hidden Greek text might be part of an ancient star catalog. Astronomical references within the text immediately drew researchers’ attention, particularly those related to the precession of the Earth’s axis — a phenomenon known as axial precession or the “wobble” of the Earth’s axis — first documented by Hipparchus.
Now, several pages of the manuscript are undergoing advanced scanning using a particle accelerator known as a synchrotron at Stanford University’s National Accelerator Laboratory in California. This technology produces ultra-precise X-rays by accelerating electrons to near-light speeds, allowing scientists to detect the chemical composition of different inks without causing any damage to the fragile pages.
The success of the technique lies in the chemical contrast between the inks. The Syriac overlay, written by medieval monks, contains iron-rich ink, while the underlying Greek text shows a calcium-based chemical signature. This difference enables researchers to separate the layers and reveal the original writing that has remained hidden for more than a millennium.
Scientists have already recovered descriptions of certain stars and references to the constellation Aquarius, one of the star groups recognized since antiquity. Researchers hope that continued scanning will uncover additional astronomical coordinates recorded by Hipparchus.
Historian Victor Gysembergh, from the French National Centre for Scientific Research (CNRS), said the findings could shed light on fundamental questions about the origins of science. He noted that the coordinates discovered so far are “astonishingly precise, especially considering they were determined with the naked eye centuries before the invention of the telescope.”
Evidence indicates that the manuscript was originally found at Monastery of St. Catherine in Sinai, Egypt — the world’s oldest continuously inhabited Christian monastery. Today, it is held in the collection of the Museum of the Bible in Washington, which carefully transported it to the laboratory for scientific analysis.
Moving the manuscript required meticulous procedures. The pages were placed in custom frames within climate-controlled containers and handled manually to prevent damage. Even the lighting in the examination room was carefully adjusted to help preserve the ink.
Despite these efforts, reconstructing the complete star map remains a monumental task. Only eleven pages have been scanned so far, while the full manuscript spans approximately 200 pages scattered across collections and libraries around the world. International collaboration will be essential to gather and study the entire set.
Nevertheless, researchers view the current progress as a rare opportunity to rediscover a scientific achievement once thought lost. After more than two millennia, Hipparchus’ star map may once again reveal how early humans viewed the cosmos—and how, relying only on the naked eye and simple methods, they were able to chart the stars that still shine above us today.
