A piece of parchment that is about a thousand years old is starting to reveal writing that scribes tried to erase long ago. Researchers in the Bay Area used powerful X-ray scanning this week to detect faint ancient Greek text hidden beneath a medieval religious manuscript, including an ancient Greek star map.
The recovered lines include star coordinates linked to Hipparchus, a second-century B.C. mathematician and astronomer whose work helped shape early scientific astronomy.
Scholars have hunted for Hipparchus’ original star measurements for years. Much of his writing did not survive as a complete work. That is why even small fragments of numbers and labels can matter.
A manuscript reused by monks
The parchment comes from a manuscript known as the Codex Climaci Rescriptus. It is a palimpsest, a document created when someone scraped away older writing and reused the page for a new text.
Parchment was costly in the Middle Ages. Books required large numbers of animal skins, and scribes often recycled pages rather than start from scratch. In this case, monks at Saint Catherine’s Monastery in Egypt’s Sinai Desert reused the parchment for a Syriac religious text connected to St. John Climacus, a monk from late antiquity.
The older Greek layer did not disappear completely. It lingered as faint smudges and traces embedded in the animal skin.
X-rays that read chemistry, not ink
The method does not rely on what the human eye can see. It relies on what remains on the page at the atomic level. Researchers scan the parchment with X-rays and measure how the materials respond. Different inks carry different chemical signatures. Those signatures can remain even after scraping.
A 1,000-year-old parchment is giving up erased secrets. Using X-ray scanning, researchers recovered hidden ancient Greek text beneath a medieval religious manuscript — including star coordinates linked to Hipparchus and references to “Aquarius.” pic.twitter.com/enu36JCqeY
— Tom Marvolo Riddle (@tom_riddle2025) January 26, 2026
Minhal Gardezi, a physics Ph.D. student working with the team, said the visible ink used by medieval scribes shows a strong iron signal. The underlying Greek writing produces a stronger calcium signal. By mapping where those elements appear, researchers can separate the layers and make the erased text stand out.
The scans create what scientists call elemental maps. Those maps show where chemical traces cluster across the page, allowing software to reconstruct letters and numbers that the eye cannot pick out.
Early results on 11 pages
The team began scanning 11 pages supplied by the Museum of the Bible in Washington, D.C., which holds part of the larger manuscript. Other sections of the codex sit in collections around the world. By the next morning, monitors showed lines of ancient Greek emerging from beneath the visible text.
Victor Gysembergh, a scholar leading the effort, said the team has already spotted the Greek word for “Aquarius” and descriptions of “bright” stars in that constellation. He said the new scans offer a level of detail that earlier imaging methods could not reach.
Multispectral photography had revealed some fragments in the past. The new X-ray approach can recover finer characters and more complete sequences of numbers, researchers said.
Handling fragile parchment with care
The work also required strict conservation steps. Elizabeth Hayslett, a conservator with the Museum of the Bible, prepared the folios for travel in controlled conditions to protect the parchment from damage. During scanning, staff kept the work area dim to reduce further fading.
Scientists also monitored the radiation dose. Uwe Bergmann, a visiting professor of X-ray science involved in the project, said each brief pulse of X-ray light hits a spot about the width of a human hair. The team kept exposure below levels they consider safe for the material, comparing it to the kind of caution used in medical imaging.
A window into the birth of science
Hipparchus is often credited with some of the earliest precise measurements of star positions. Scholars say his work helped lay the groundwork for later astronomy and navigation.
The recovered coordinates may also speak to a long-running debate about the Roman astronomer Ptolemy. Historians have argued for years over how much Ptolemy relied on earlier data and whether he copied Hipparchus too closely.
Gysembergh said comparisons between the newly recovered measurements and Ptolemy’s surviving records could show when Ptolemy used Hipparchus’ observations and when he relied on other sources.
The next phase will shift from imaging to reading. Scholars of ancient Greek will work through the recovered text and numbers to rebuild more of the star catalog and confirm what the long-hidden coordinates can say about early astronomy.
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