The Nebra sky disk is a bronze disk of around 30 cm diameter and a weight of 2.2 kg, with a blue-green patina and inlaid with gold symbols.
These are interpreted generally as a sun or full moon, a lunar crescent, and stars (including a cluster interpreted as the Pleiades). Two golden arcs along the sides, marking the angle between the solstices, were added later. A final addition was another arc at the bottom surrounded with multiple strokes (of uncertain meaning, variously interpreted as a Solar Barge with numerous oars, as the Milky Way, or as a rainbow).
The disk is attributed to a site near Nebra, Saxony-Anhalt, in Germany, and associatively dated to c. 1600 BC. It has been associated with the Bronze Age Unetice culture.
The disk is unlike any known artistic style from the period, and was initially suspected of being a forgery, but is now widely accepted as authentic.
The precise dating of the Nebra skydisk depended upon the dating of a number of Bronze Age weapons, which were offered for sale with the disk and said to be from the same site. These axes and swords can be typologically dated to the mid 2nd millennium BC. Radiocarbon dating of a birchbark particle found on one of the swords to between 1600 and 1560 BC confirmed this estimate. This corresponds to the date of burial, at which time the disk had likely been in existence for several generations.
According to an initial analysis of trace elements by x-ray fluorescence by E. Pernicka, then at the University of Freiberg, the copper originated at Bischofshofen in Austria, while the gold was thought to be from the Carpathian Mountains. A more recent analysis found that the gold used in the first phase was from the river Carnon in Cornwall, United Kingdom.The tin content of the bronze was also from Cornwall.
The disk is possibly an astronomical instrument as well as an item of religious significance. The blue-green patina of the bronze may have been an intentional part of the original artifact.
It reconfirms that the astronomical knowledge and abilities of the people of the European Bronze Age included close observation of the yearly course of the Sun, and the angle between its rising and setting points at summer and winter solstice. While much older earthworks and megalithic astronomical complexes such as the Goseck circle or Stonehenge had already been used to mark the solstices, the disk is the oldest known “portable instrument” to allow such measurements. Pásztor, however, sees no evidence that the disk was a practical device for solar measurements.
Nebra disk can be linked to the solar calendar reconstructed by Alexander Thom from his analysis of standing stone alignments in Britain.