An early medieval manuscript contained the earliest complete map of the stars

Scientists have discovered a fragment of the world's oldest known complete star map. Part of the map, found under text on a sheet of medieval parchment, is thought to be a copy of a long-lost star catalogue from the workshop of the Greek astronomer Hipparchus in the second century BC.

The fragment was hidden beneath nine leaves of the Codex Climaci Rescriptus kept in the monastery of St. Catherine on the Sinai Peninsula. It is a palimpsest where the original texts were scraped from the parchment and replaced with new ones. Researchers initially thought they would find even older Christian texts underneath the newer Aramaic text, but multispectral imaging revealed something much more surprising: numbers giving the longitude and latitude in degrees of the constellation Corona Borealis. Crown) and the coordinates of the stars in its outermost corners.

"I was very excited from the beginning," said team leader Victor Gysembergh, a scientific historian at the French National Centre for Scientific Research (CNRS) in Paris. "It was immediately clear that we had the coordinates of the stars." The researchers' excitement grew when the coordinates allowed them to estimate fairly accurately the date when the coordinates were written down - probably 129 BC.

Hipparchus lived from about 190 BC to 120 BC. He spent most of his later life making astronomical observations from the island of Rhodes. Not much documentation remains of him, but historical texts by his followers credit him with a number of impressive scientific advances. For example, accurate models of the motions of the sun and moon, the invention of the brightness scale for measuring stars, the development of trigonometry, and the probable invention of the astrolabe for calculating the exact position of celestial bodies.

Hipparchos catalogued some 850 stars in the night sky and recorded their exact locations and degrees of brightness. By comparing his own complete star chart with more fragmentary measurements of individualof stars by earlier astronomers, Hipparchos realised that the distant stars had been displaced by 2 degrees from their original positions. He concluded that the apparently fixed positions of the stars were shifting: the Earth was in motion, rotating on its axis like a pinwheel by 1 degree every 72 years.

The scientists took 42 photographs of each of the nine sites using different wavelengths. They then scanned the photos using computer algorithms that showed the original text hidden from human eyes. After reading the coordinates, the experts used the scholar's original idea of planetary precession of the Earth's axis, but in reverse. They thus got the constellation Corona Borealis back to the year when it shone in the sky at the exact spot where the hidden text described it.

The date of the original starry sky record was therefore 129 BC, but it remained to be determined exactly when the copy of the map was made. By dating the nine folios by paleographic identification of points of historically different writing styles, the text was dated to the 5th or 6th century AD. Thus, copies of Hipparchus' catalogue were in use more than 700 years after his death!

By comparing the older record with another separate medieval Latin manuscript called Aratus Latinus, which was also supposed to contain a line ofst copies of Hipparchus' original catalogue, the researchers confirmed that the Aratus manuscript's coordinates for the constellations of the Dragon, the Great Bear and the Little Bear also date from 129 BC. AD. They thus provide fairly convincing, if indirect, evidence that the newly found portion of the map comes from the same source.

"The new fragment makes it much, much clearer," said Mathieu Ossendrijver, a historian of astronomy at the Free University of Berlin"This star catalogue, which had been floating around in the literature as almost a hypothetical thing, has now become very concrete."

Experts hope to scan more pages of the codex for further research. Most of its 146 folios are currently owned by American billionaire and Hobby Lobby founder Steve Green. It is on display at his Museum of the Bible in Washington. In 2021, Hobby Lobby was forced by federal authorities to give up 17,000 smuggled artifacts originally looted during the Iraq War.

Scientists believe there may be other treasures, not just pages of the star catalog, hidden in the more than 160 other palimpsests at St. Catherine's Convent. Earlier analyses have led to the discovery of unknown Greek medical texts, including surgical procedures, recipes for medicines and descriptions of medicinal plants, for example.

Roman Nemec

Sources: livescience.com, nature.com, journals.sagepub.com

St. Catherine's Monastery at Sinai