Hipparchus of Nicaea (190-120 BC) was the author of the first stellar catalog. His work contained the position of 850 stars in 48 constellations, supposedly transmitted through universal ecliptic coordinates, a system that allows the position of a celestial object to be determined with respect to the Aries Point (the place where the sun passes from the southern hemisphere to the northern ).
But his text disappeared, disappeared from the face of the earth, nobody knew where he could be hidden. For centuries it was talked about through the references that Ptolemy left in books VII and VIII of his Almagest, written 400 years after Hipparchus. The whereabouts of the original, however, remained a mystery. Until an English university professor commissioned a class assignment from his students, as detailed in an article published in the Journal for the History of Astronomy.
In 2012, the biblical historian Peter Williams, from the University of Cambridge, asked his students to study the Codex Climaci Rescriptus, a compendium of up to 11 manuscripts found in the Orthodox monastery of Saint Catherine (Sinai Peninsula). Eight of the texts are written in Aramaic during the Middle Ages and the rest in classical Greek. The codex is a palimpsest, a group of scrolls from which the original content has been removed and new information written on top.
A student named Jamie Klar was the first to notice that under the Aramaic lines there were half-erased phrases, something common during the Middle Ages because parchment was an expensive and difficult material to obtain. Five years later, a group of researchers decided to photograph those passages using different wavelengths.
Once the original texts were obtained, Meter Williams himself was the one who dedicated himself to unraveling its mysteries during the confinement caused by the Covid-19 pandemic. On nine pages of the Codex Climaci there was astronomical information: passages by the astronomer Eratosthenes of Cyrene (276-194 BC), a poem from the third century that described constellations or a paragraph full of numbers.
The Cambridge professor contacted his colleague Victor Gysembergh, from the French National Center for Scientific Research (CNRS), who soon found out that those figures correspond to coordinates in space and, more specifically, that they described the position of the stars. stars that form the small constellation Corona Borealis.
But it wasn't just that. Hidden beneath those medieval texts was Hipparchus' missing Star Catalogue. And his study has led to important findings. The first, for example, is that the coordinates used by the Greek scientist were the equatorial ones (which take the celestial equator and the vernal equinox as reference) and not the ecliptic ones.
It was also possible to confirm that the passages of Claudius Ptolemy (100-170 AD) on the positions of the fixed stars are not a mere "copy" of the data in the Catalog of Hipparchus from the 2nd century BC, which were much more accurate than those compiled by his successor centuries later. Also, the observations of the four constellations are different.
For the team of researchers, this important discovery sheds new light on the history of astronomy in ancient times and on the beginnings of the history of science. "It illustrates, above all, the power of cutting-edge techniques, such as multispectral imagery, whose application to illegible palimpsests could save lost philosophical, medical, or horticultural texts from oblivion," they conclude.
