Oldest Map of the Night Sky Feared to Have Been Lost; May Have Been Discovered Recently in Medieval Parchment

The earliest attempt to map the night sky may have just been found on medieval parchment preserved at the St. Catherine's Monastery on the Sinai Peninsula in Egypt. Scholars have discovered what seems to be part of the Greek astronomer Hipparchus' long-lost star catalog hidden beneath Christian texts, which they have searched for centuries.

James Evans, a historian of astronomy at the University of Puget Sound, said that the "rare" and "remarkable" map proves that Hipparchus indeed mapped the heavens centuries before anyone else attempted. It also shows the crucial moment in the birth of science when astronomers start measuring and predicting the sky instead of just observing them.

Once Lost, Now Found: Finding Hipparchus' Map of the Night Sky

It was in 2012 when Jamie Klair, the student of leading biblical scholar Peter Williams, noticed something bizarre behind the letters of the Christian manuscript that he was analyzing at the University of Cambridge, Science Alert reports. The famous passage was often attributed to Eratosthenes, the astronomer and chief librarian at the Library of Alexandria.

Five years later, multispectral imaging of the parchment revealed nine folios of pages that contained text written over. Williams studied the results carefully during the second year of the pandemic and noticed odd numbers in St. Catherine's Monastery folios. He sent the page to scientific historians in France, who were shocked to see star coordinates.

"It was immediately clear we had star coordinates," says historian Victor Gysembergh from the French national scientific research center to Nature's Jo Marchant.

Experts cannot tell with full certainty that they know who wrote the coordinates, but they do know that the Hipparchus was working on a star catalog of the western's night sky between 162 and 127 BCE.

Several historical texts have referred to him as "the father of astronomy" and credited him for discovering how the Earth wobbles on its axis, known as precession, and for being the first to calculate the Sun's and Moon's motions.

Researchers worked backward to trace out Earth's precession at the time the map was made and found that the stars' coordinates roughly matched Earth's expected precession in 129 BCE, within the lifetime of Hipparchus. Also, many of the coordinates in the parchment matched his only work left, the Commentary on the Phaenomena, though the text can be difficult to decipher.

The Birth of Astronomy

The discovery of what was thought to be the lost earliest known map of the night sky gives a renewed opportunity for astronomers to see what Hipparchus was working on, Nature reported.

It sheds light on a key development in Western civilization, the "mathematization of nature," that scholars seek to understand how people go from simply describing the sky to measuring, calculating, and predicting them.

Mathieu Ossendrijver, a historian of astronomy at the Free University of Berlin, agrees that Hipparchus was a pivotal figure in "turning astronomy into a predictive science," as earlier astronomical writers do not care about numerical accuracy in describing orbits and celestial spheres.

Hipparchus is thought to be inspired by Babylonian astronomers who had no interest in how the Solar System was arranged in three dimensions. Instead, they made accurate observations and developed mathematical methods to create celestial bodies' models and predict events' timing, such as the lunar eclipse.

The team hopes to further uncover the star coordinates in the parchment as imaging techniques improve to gather a larger data set to study. They have yet to decipher several parts of the Codex Climaci Rescriptus.

They published their findings in the study, titled "New evidence for Hipparchus' Star Catalogue revealed by multispectral imaging," in the Journal for the History of Astronomy.

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