Castelliere di Rupinpiccolo is an ancient hill fort in the province of Trieste, Italy. The hill fort was inhabited in the Middle Bronze Age, and archaeological evidence suggests that occupation continued through the Iron Age until it was abandoned around the 5th century AD.
A press release by the Italian National Institute of Astrophysics (INAF) said that two large circular stones with a diameter of 50 centimeters were recently discovered at the entrance of the hill fort.
According to Paolo Molaro of INAF and researchers from the Ca’ Foscari University of Venice and ICTP, one of the stones represents the sun, while the other is a carved celestial map dating back to the 4th century BC.
A study of the stones was published in the German astronomy journal Astronomische Nachrichten. The authors of the study found that the celestial map depicts the sky above the Rupinpiccolo from around 2500 years ago, making this discovery one of the oldest known celestial maps found in Italy.
The team identified 29 engravings on the stone, corresponding exactly to the constellations Scorpius, Orion, Pleiades and Cassiopeia. Based on the angle of the cut marks on the stone, the researchers suggest that the engravings were probably made by the same person using a hammer and a primitive metal chisel with a 6-7 mm tip.
A particular star, identified as Theta Scorpii and engraved in stone, has disappeared from view in what is now Castelliere di Rupinpiccolo due to its low position on the horizon. However, when researchers used the Stellarium program to simulate the night sky, they discovered that this star could be observed from the ancient hill fortress around 400 BC.
The authors of the study suggest that it could actually be a representation of a supernova. This is a temporary phenomenon that in ancient times would suddenly appear in the night sky for days or months and then fade away.
If this is indeed the case, the researchers link the focal point in the night sky to the 29th engraving, suggesting that it could potentially reveal a black hole left behind by the supernova explosion.