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Medieval Palimpsest Reveals Ancient Star Map

Updated: Nov 29, 2022

Scholars recently uncovered a remarkable map of the cosmos that had been hiding for centuries beneath the text of a medieval manuscript.

When searching for evidence of an older Christian text hiding underneath the text of the Codex Climaci Rescriptus at the Museum of the Bible in Washington, DC, researchers were shocked to find Greek lettering instead.

Describing stories from the Old and New Testaments, the Codex was written by scribes at St. Catherine’s Monastery (above) in Egypt around the 10th century.

The book was a palimpsest, meaning that the parchment had been repurposed by scraping off the original ink so the medieval scribes could reuse the valuable parchment underneath. To find out what the original manuscript might have been, during the summer of 2012, students and their Cambridge University professor started submitting the pages to different wavelengths of light.

When a student uncovered under the medieval text a fifth-century passage about star origin myths by the Greek astronomer Eratosthenes, they knew they were onto something spectacular.

So the students and professor continued scanning in the pages over the following years. Finally, during the pandemic lockdown, the professor had the time to combine the images and analyze the findings. What he found was shocking: in Greek was written the length and width, in degrees, of the constellation Corona Borealis, as well as the coordinates for other stars in the constellation.

By comparing in what year was the constellation existed at those coordinates, the professor and other historians were able to determine that the underlying text was written in 129 BC, the same year when it was believed that the legendary Greek astronomer Hipparchus was cataloging the location of 850 visible stars in the night sky.

Although scholars know that Hipparchus’ star catalog was revered and studied for hundreds of years, no extant copy has survived to this day, leading some to postulate that the star catalog was just a myth. Based on this new evidence, however, it is now believed that Hipparchus was the original author of the text found underneath the medieval text. Since the underlying text was written sometime during the fifth century AD, it was most likely transcribed from perhaps one of his second-century BC star catalogs.

Most likely using a sighting tube or an armillary sphere, Hipparchus' calculations as described in the Codex was correct to within one degree. This was an astonishing feat for that time, as the telescope had not yet been invented.

Researchers now believe that additional pages from Hipparchus' original star catalog may be hiding in the more than 160 palimpsests still housed at St. Catherine's Monastery or at the DC museum.

The Museum of the Bible is owned by Hobby Lobby founder Steve Green, who purchased the Codex in 2010 at auction from Westminster College at Cambridge University.


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