More than 2,100 years ago, Greek astronomer Hipparchus mapped out the stars — and for a long time, this had been considered humanity’s earliest attempt to assign numerical coordinates to stellar bodies. But despite its fame, the treatise was only known to exist through writings of another ancient astronomer named Claudius Ptolemy, who compiled his own celestial inventory some 400 years later. 

Until now, that is.

Researchers believe they’ve found fragments of Hipparchus’ lost, historical document hidden in a book of medieval Greek manuscripts. 

“This new evidence is the most authoritative to date and allows major progress in the reconstruction of Hipparchus’ Star Catalogue,” reads a study on the find published in the journal History of Astronomy this week. Beyond cartography, the discovery could shed new light on the overall work of Hipparchus — who’s also known as the father of trigonometry — and on the history of astronomy. 

Hipparchus is often considered the greatest astronomer of ancient Greece. Parts of his star map appear to have shown up in the Codex Climaci Rescriptus, a book of Syriac texts in which pages were erased so they could be rewritten on, but still bear visible traces of their earlier form. This particular palimpsest is housed at the Greek Orthodox St Catherine’s Monastery on Egypt’s Sinai Peninsula.

Teams from the Early Manuscripts Electronic Library, the Lazarus Project and the Rochester Institute of Technology revealed the erased text and numbers using different wavelengths of light, a technique known as multispectral imaging. 

Researchers from Sorbonne Universite and the University of Cambridge were then able to decipher the descriptions of four constellations. Not only did this seem to unveil Hipparchus’ star maps, but the team also says the newly revealed numerical evidence is highly consistent with real stellar coordinates. This would make Hipparchus’ Catalogue more accurate than Ptolemy’s much later version. 

Further, as cutting-edge digital technologies continue to recover vital cultural heritage lost to damaged and deteriorating documents, the study scientists say the Codex Climaci Rescriptus could yet reveal even more of Hipparchus’ stellar observations.