If the celestial disk of Nebra, registered since 2013 in the UNESCO “Memory of the World” register, testifies to the ingenuity of the artisans of the Bronze Age, its manufacturing process remained very mysterious for the moment. Recent metallographic analyses, the results of which were published in Scientific Reports on November 21, 2024, reveal that more than 3,600 years ago, fabricators mastered techniques much more advanced than estimated by experts, requiring mastery exceptional bronze processing.
The celestial disk of Nebra. Collection of the National Museum of Prehistory (Landesmuseum für Vorgeschichte) in Halle (Saxony-Anhalt Germany). Wikimedia Commons / Anagoria / CC BY
The Nebra disk, a window on the Bronze Age
As its name suggests, the artifact was discovered near the town Nebra-sur-Unstrut (State of Saxony-Anhal, Germany) in 1999. It is a bronze disc measuring 32 centimeters diameter, decorated with gold inlays representing celestial motifs: the Sun, the Moon and stars, one cluster of which is identifiable as the Pleiades. Considered the oldest known representation of the cosmos, the medium reflects both the astronomical knowledge and symbolic beliefs of Bronze Age societies.
Its use remains debated; it could have served as an astronomical tool, a ritual or symbolic object… In any case, despite its “simple” appearance, forging such a disk with a thickness of a few millimeters was far from being a trivial task for its ancients. users. So, in an attempt to discover their age-old techniques, a small sample taken in 2002 from its outer zone was re-examined, using more modern methods (energy dispersive X-ray spectroscopy, backscattered electron diffraction, etc. .).
Former founders with exceptional know-how
The study ultimately reveals that Nebra’s celestial disk was designed using a complex and sophisticated hot forging process: starting from a perfectly calibrated casting, the metal had to be heated to around 700°C, forged then annealed ten times in a row (at least) to make it malleable and reach its final dimensions. A process which was confirmed through experimental tests, including the creation of a replica from a cast blank, carried out by experienced boilermaker Herbert Bauer. It also had to perform more cycles to obtain an object comparable to the original disk.
Perhaps Bronze Age artisans mastered specific techniques or tools that are no longer used today. They were in any case “exceptional cross-country skiers”Who “thanks to their extensive experience and know-how […] were capable not only of mass-producing numerous axes, but also of forging a unique piece like the celestial disc of Nebra”write the authors of the research in a press release from the Regional Office for Monument Conservation and Archeology of Saxony-Anhalt.
According to Dr Harald Meller, lead archaeologist on the project, while this discovery illustrates the high level of development of the art of metalworking during the Early Bronze Age, it also demonstrates the importance of “re-examine apparently well-known findings when new methods become available”. These studies could bring to light unsuspected treasures on objects that already appeared to be fully explored.
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