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Part of Hipparchus’ Lost Star Catalog Found Hidden in Medieval Scroll

Hipparchus’ legendary star catalog, thought to be lost, was discovered hidden in a medieval scroll that was originally kept in the library of the Orthodox Monastery of St. Catherine in Sinai, Egypt.

Researchers have discovered what appears to be part of Hipparchus’ long-lost star catalog – the earliest known attempt to map the entire sky – hidden beneath Christian texts.

Hipparchus, the Greek astronomer, is often called the “father of astronomy”. Among other accomplishments, he is credited with discovering the Earth’s precession (how it wobbles on its axis) and calculating the motions of the Sun and Moon. According to historical texts, Hipparchus also compiled a catalog of stars between 162 and 127 BCE.

Scholars have been searching for this catalog for centuries. Now, using a technique called multispectral imaging, they’ve found what appear to be the earliest known remnants of Hipparchus’ star catalogue.

Multispectral imaging is a method that takes visible blue, green, and red images and combines them with an infrared image and an X-ray image of an object. This can expose tiny specks of pigment as well as hidden writings or designs that have been covered by multiple layers of paint or ink. For example, researchers have already used this method to uncover the hidden text on four Dead Sea Scroll fragments that were thought to be blank at the time.

The palimpsest was discovered at Saint Catherine’s Monastery on the Sinai Peninsula in Egypt.

The excerpt is published online this week in the astronomy history review.

The current article is the result of research into the Codex Climaci Rescriptus, a palimpsest originating from Saint Catherine’s Monastery on Egypt’s Sinai Peninsula.

The majority of the manuscript’s 146 leaves, or folios, which originally belonged to St. Catherine’s Greek Orthodox Monastery in the Sinai Peninsula, Egypt, are now in the possession of the Museum of the Bible in Washington, DC. The pages contain the Codex Climaci Rescriptus, a collection of Syriac texts written in the 10th or 11th centuries. But the codex is a palimpsest: a scroll that has been scraped from an older text by the scribe so that it can be reused.

It was common practice at the time to scrape clean old parchment for reuse, and that’s what was done with the codex. Scholars initially believed the older scriptures to be more Christian texts. But in 2012, when Cambridge University professor and Bible expert Peter Williams assigned his summer students to study the pages for a special project, one of them found a Greek passage from the astronomer Eratosthenes.

Williams contacted researchers at the University of Rochester in New York and the Early Manuscripts Electronic Library in California to perform multispectral imaging of the codex pages in 2017.

A leaf from the Codex Climaci Rescriptus in the Green Collection.
A leaf from the Codex Climaci Rescriptus in the Green Collection. Wikipedia

The method resulted in a total of nine folios relating to astronomy that were written between the 5th and 6th centuries, including not only Eratosthenes’ passage on star myths, but also a well-known poem (Phaenomena , written around the 3rd century BCE) which describes the constellations.

During the pandemic lockdown, Williams spent a lot of time studying the resulting images, and one day he noticed what appeared to be the coordinates of the constellation Corona Borealis. He immediately informed science historian Victor Gysembergh of the CNRS in Paris of his discovery.

“I was very excited from the start”, Gysembergh says Nature. “It was immediately clear that we had star coordinates.”

But could Hipparchus be the author of this passage? The authors cite a number of pieces of evidence that appear to link the text to the Greek astronomer, though they are hesitant to assign the text any specific attribution. For example, some of the data is recorded in an odd way that is consistent with the only other surviving work by Hipparchus. The observations recorded in the text were most likely made around 129 BCE, when Hipparchus would have been working on his catalog, according to the authors’ analysis of the astronomical maps.

DOI: Journal of Astronomical History, 2022. https://doi.org/10.1177/00218286221128

Cover photo: This cross-fade edit shows a detail of the palimpsest in ordinary lighting; under multispectral analysis; and with a reconstruction of the hidden text.Credit: Museum of the Bible (CC BY-SA 4.0). Photo by Early Manuscripts Electronic Library/Lazarus Project, University of Rochester; multispectral processing by Keith T. Knox; tracings by Emanuel Zingg.