Nebra Sky Disc: The world's oldest depiction of astronomical phenomena — and it may depict the Pleiades

The Nebra Sky Disc was discovered in an artifact hoard in 1999, when metal detectorists illegally excavated it from an ancient religious site on a hill near Nebra, a town in the German state of Saxony-Anhalt. After police recovered the disc in 2002, archaeologists studied the unique object, revealing it's up to 3,800 years old and the world's oldest depiction of astronomical phenomena. (The next oldest is a star map on the ceiling of an ancient Egyptian tomb from about 3,500 years ago.)

The Sky Disc was crafted from about 8.8 pounds (4 kilograms) of bronze, according to the State Museum of Prehistory in Halle, Germany, where the object is on display. The bronze was flattened into a disc 12.6 inches (32 centimeters) in diameter and then decorated with 1.8 ounces (50 grams) of gold inlay representing a boat, a crescent moon, a full moon or a sun, and a series of stars.

Based on the style of the axes and the carbon dating of wood in the hilts of swords recovered along with the disc in the metal hoard, experts think the Sky Disc was buried around 1600 B.C., during the Early Bronze Age, but it may have been created two centuries earlier.

Some research has questioned the disc's authenticity, saying that it probably didn't come from Nebra and was about 1,000 years more recent, based on a soil and chemical analysis of the artifact. A subsequent study countered those claims and found that the disc was authentic and from Nebra but that it was made in several stages.

Close examination of the disc revealed that it was made in at least five phases. Initially, the bronze disc included the full moon or sun, the crescent moon and 32 stars. Then, two arcs were placed on each side of the disc. A third arc, perhaps representing a boat, was then added to the bottom. In the fourth phase, the rim of the disc was perforated, suggesting it may have been attached to a support, like a pole for ceremonial use. Finally, the left arc was removed before the disc was buried with the metal hoard. But experts don't know exactly when the disc was made or how much time passed between the phases of decoration.

The Nebra Sky Disc appears to represent the night sky, with several stars forming the Pleiades, or "Seven Sisters," star cluster. The golden arcs on each side of the disc may represent the horizons, marking the summer and winter solstices, and the boat may be a mythical one that brought the sun across the sky from east to west in the daytime and back at night.

By aligning the Sky Disc with the plateau on Mittelberg Hill, where it was found, the western horizon arc aligns with the Brocken, a high mountain that the sun disappears behind on the summer solstice. This suggests the Sky Disc may have been used to keep track of important astronomical dates in prehistory.

But who used the Sky Disc and who buried it are still mysteries, partly because it was recovered by treasure hunters and not in a scientific excavation. The treasure hunters damaged the gold sun or full moon, scratched the surface, and cleaned it improperly. Given the numerous well-furnished burial mounds of important people that dotted the landscape of central Germany as early as 2000 B.C., however, perhaps the Sky Disc once belonged to a Bronze Age chieftain.

For more stunning archaeological discoveries, check out our Astonishing Artifacts archives.