The Nebra Sky Disc is a 3,600-year-old artifact widely recognized as the oldest known depiction of the cosmos. Recent findings published in Scientific Reports have shed new light on the intricate techniques used to craft this extraordinary Bronze Age artifact.

The 3,600-year-old Nebra Sky Disk. Credit: Frank Vincentz

The Sky Disc was discovered in 1999 on the Mittelberg hill near Nebra, Germany, by treasure hunters Henry Westphal and Mario Renner. Found alongside bronze swords, axes, a chisel, and spiral armbands, the artifact was sold to private dealers before being recovered in 2002 through a police sting operation. It is now housed at the State Museum of Prehistory in Halle, Germany, and has been part of UNESCO’s “Memory of the World” register since 2013.

Adorned with gold inlays depicting celestial bodies such as the Sun, Moon, and stars, the disc is attributed to the Únětice culture, which thrived during the Central European Bronze Age (2300–1600 BCE). Despite its relatively small size—measuring about 12 inches (31 cm) in diameter and just a few millimeters thick—it represents a profound understanding of astronomy and metalworking.

The recent study by the State Office for Heritage Management and Archaeology Saxony-Anhalt, in collaboration with the Otto von Guericke University Magdeburg and DeltaSigma Analytics GmbH, reveals that the disc was crafted through a highly sophisticated H๏τ-forging process. Using advanced metallographic techniques, including energy-dispersive X-ray spectroscopy, electron backscatter diffraction, and light microscopy, researchers uncovered a manufacturing process involving approximately ten cycles of heating to 700°C, forging, and annealing.

The Nebra Sky Disc with the marked sample extraction point. Credit: J. Lipták, Munich, Reproduced with permission by State Office for Heritage management and Archaeology, Saxony-Anhalt—State Museum of Prehistory

Dr. Harald Meller, State Archaeologist, remarked, “That the investigations continue to produce such fundamental new findings more than 20 years after the Sky Disc was secured not only once again demonstrates the extraordinary character of this find of the century, but also how highly developed the art of metal processing was already in the Early Bronze Age.”

To better understand the craftsmanship, renowned coppersmith Herbert Bauer created a replica of the Sky Disc using a cast blank. Bauer’s experiments revealed that the original artifact required fewer forging cycles than the replica, suggesting that the original cast blank was both larger and thinner. These findings underscore the remarkable skills of Bronze Age metalworkers, who were not only proficient casters but also adept at advanced techniques such as H๏τ forging.

Pictures of the different replicas. Credit: Dieck, S., Michael, O., Wilke, M. et al. Sci Rep (2024)

Archaeologists believe the Sky Disc played a significant role in the agricultural and ritual practices of the Únětice culture, serving as a tool for astronomical observation and a symbol of cosmic order. Its layered creation over four distinct phases and eventual deposition as a ritual offering highlight its cultural and spiritual importance.

Dr. Meller emphasized, “The Sky Disc shows how important it is to re-examine seemingly well-known finds when new methods become available.”

These latest findings confirm that early Bronze Age artisans possessed advanced knowledge of metallurgy, enabling them to create unique and enduring works of art like the Nebra Sky Disc—a true marvel of human innovation.

More information: Dieck, S., Michael, O., Wilke, M. et al. (2024). Archaeometallurgical investigation of the Nebra Sky Disc. Sci Rep14, 28868. doi:10.1038/s41598-024-80545-5