An ancient catalog of astronomy discovered thanks to advanced technology

Thanks to multispectral imagery, researchers have brought to light extracts from the catalog of Hipparchus, a Greek astronomer who had succeeded in measuring the position of stars in the sky more than 2000 years ago, with remarkable precision.

What is the relationship between the star catalog of the Greek astronomer Hipparchus, written between -170 and -120 BC, and multispectral imaging, a cutting-edge technology? A priori none and yet, this ancient catalog would have remained hidden without the use of these modern means by the teams of the Early Manuscripts Electronic Library, the Lazarus Project and the Rochester Institute of Technology.

Indeed, part of the catalog was hidden in a set of parchments called Codex Climaci Rescriptus. These scrolls have been erased and reused for new scriptures. This ancient form of recycling is called the palimpsest. Thus, one of the parchments contained a poem in ancient Greek, with excerpts from Hipparchus’ star catalog in the comments. But alas, it had been erased in the Middle Ages and subsequently preserved in Egypt, at the monastery of Saint Catherine of Sinai.

© CC / Denysmonroe81

The catalog might have remained invisible if not for the use of multispectral imaging, which involves taking pictures under different electromagnetic wavelengths, to discover what the human eye cannot see. Indeed, the eye only sees the visible spectrum, with a wavelength of 400 nm to 700 nm, but does not perceive infrared (700 nm to 10,000 nm), nor ultraviolet (200 nm to 400 nm). And even if a text has been erased from a parchment, there are still traces that multispectral imagery can find. More important: the method is non-intrusive and does not damage the object to be analyzed.

This technology is used in the medical field, but also in the field of art. It allows, for example, to analyze the different layers of paint that the painter used to create his painting, or even to detect a sketch that was subsequently covered. For example, Lumière Technology used a multispectral camera to analyze Leonardo da Vinci’s Mona Lisa. Thanks to the use of algorithms, she was able to reconstruct the original colors of the painting, which have unfortunately been modified by the yellowing of the varnish that covers the canvas.

Mona Lisa Colors
The image on the right shows the original colors © Lumière Technology

In the case of the Codex Climaci Rescriptus, multispectral imaging revealed notes over 2100 years old, which then had to be analyzed and attempted to be deciphered. This task was entrusted to researchers from the Léon Robin Center for Research on Ancient Thought (CNRS/Sorbonne University) and their British colleagues from Tyndale House in Cambridge. Eventually, descriptions of four constellations could be deciphered.

Surprise: Hipparque’s data, which represent measurements of the position of stars in the sky, are true to the nearest degree. Thus, his catalog would be much more accurate than that of Claudius Ptolemy, another ancient astronomer whose work was carried out nearly 400 years after that of Hipparchus.

Thus, multispectral imagery could save lost texts from oblivion, which would delight scientists and historians.

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