The world’s oldest star map was found hidden in an ancient codex


In 2012, a student at Cambridge University identified what he suspected was an ancient Greek star map hidden behind text in a medieval codex. Compiled with astronomical data from the 2nd century AD, this is the oldest celestial chart ever discovered.

In the modern digital world, the task of Identifying stars, planets and satellites, and working out what to do with plants depending on where the moon is in its cycle, is the labor of apps. Star Map Tracker, Star Gazer and Stellarium Mobile all bring the night sky alive at the touch of a button.

In ancient times, people with higher than average IQs often attempted to record the passage of the stars using only their eyes, crude wooden tools and mathematics. Today, we celebrate an astronomical discovery from the old analogue world as scientists announce “the oldest star chart ever discovered.”

Woodcut Illustration of Hipparchus observing the sky with a telescope from Alexandria. ( Archivist / Adobe Stock)

Rediscovering the Lost Greek Star Chart

Hipparchus was the famous Greek mathematician, astronomer and geographer who lived in the 2nd century BC. Not only was Hipparchus the father of trigonometry but he also worked out the great cycle known as precession of the equinoxes. He calculated that the gradual shift (wobble) in the orientation of Earth’s axis of rotation takes about 26,000 years to complete a cycle.

Cambridge student Jamie Klair originally came across a Greek passage associated with Eratosthenes, who was a librarian and chief astronomer at the legendary Library of Alexandria. This was found on a parchment in the archives of St. Catherine’s Monastery on Egypt’s Sinai Peninsula. Then, in 2012, Peter Williams, a biblical scholar at Cambridge University, identified what he suspected was Hipparchus’s attempt to map the entire night sky hidden within the document.

St. Catherine Monastery in Egypt, where the medieval codex was discovered. ( efesenko / Adobe Stock)

When Modern Technology Reveals Ancient Secrets

According to a recent study published in the Journal for the History of Astronomy , a team of scientists applied multispectral imaging in 2017 to reveal “nine folios of pages containing hints of a text that had been written over.”

During the 2021 lockdowns, student Peter Williams spent endless hours inspecting the hidden text on the parchment found in the St. Catherine’s Monastery and he noticed “odd numbers” hidden within the folios.

Perplexed as to what these numbers might have represented, but suspecting they were the coordinates of celestial bodies, Wiliams sought a second opinion from the French historian Victor Gysembergh at the French National Scientific Research Center (CNRS) based in Paris. According to a report in Nature, Gysembergh said “it was immediately clear we had star coordinates.”

The medieval codex found in the archives of St. Catherine’s Monastery under ordinary lighting. (Museum of the Bible / CC BY-SA 4.0 )

Clearing Up Historical Misinterpretations

The Cambridge researchers took Earth’s precession and worked the cycle backwards. They discovered the coordinates of the stars on the ancient star chart roughly matched the precessional angle of our planet around 129 BC, during the time Hipparchus was working on a star chart.

Furthermore, star coordinates in the hidden text found at St. Catherine’s Monastery in Egypt match those left behind by the great astronomer in his Commentary on the Phaenomena, belonging to the constellations Ursa Major, Ursa Minor and Draco.

Until multispectral imaging revealed the set of lost numbers printed behind more recent text on the lost parchment in St. Catherine’s Monastery, the oldest known star chart was compiled in the 2nd century AD by the Greek astronomer Claudius Ptolemy. This recent discovery pushes the oldest known star chart back almost 400 years to the 2nd century AD.

The medieval parchment with tracings of the older writing as revealed by multispectral analysis, is believed to be the oldest star chart ever discovered. (Museum of the Bible / CC BY-SA 4.0 )

Newly Discovered Star Chart Brings End to Speculation

It is not yet clear who wrote the recent version of Hipparchus’ star chart. However, Dr. Mathieu Ossendrijver, a historian of astronomy at the Free University of Berlin, told Nature that the star chart “has been hovering in the literature as an almost hypothetical thing.” Now, having identified Hipparchus’ work using multispectral imaging, what was once a thing of speculation “has become very concrete,” according to Ossendrijver.

This new discovery represents the oldest star chart ever discovered. However, it should be considered that the earliest star constellation ever recorded by humans was scratched onto the face of a mammoth tusk tablet some 32,500 years ago.

Featuring a human-like figure with arms and legs outstretched shaped like the constellation Orion, Dr. Michael Rappenglueck, formerly of the University of Munich, told BBC in 2003 that mysterious notches carved on its sides and on its back “could be a primitive pregnancy calendar ” used to estimate when a pregnant woman would give birth.

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