An unusual Greek coin – minted around 120 BC – might have commemorated an occultation of Jupiter by the moon, according to a Classics professor from the University of Windsor in Canada. An occultation is an event when, in the course of its orbit around Earth, the moon happens to pass in front of a star or planet and block it temporarily from view – in this case, the planet Jupiter.
Robert Weir is a Classics professor with an interest in astronomy and ancient coins. He became interested in the coin shown at left, which depicts an ancient king, Antiochos VIII, ruler of the Seleucid Empire, in what is now southeastern Turkey. It was Antiochos VIII who minted this coin. On its reverse side, shown on the image here, there is a depiction of Zeus, Greek king of the gods, holding a sceptre in his left hand. Above the god’s head is an image of a crescent moon, and his right arm is outstretched with a starlike figure (possibly Jupiter) hovering just above his palm.
Professor Wier was curious why Antiochos VIII would mint a piece of currency with such an unusual drawing. He told Archaeology Daily News:
I did some calculations to see what was visible from Antioch, the capital of the Seleucid Empire. I came up with some interesting patterns.
He found that on January 17, 121 BC, the city’s residents would have seen Jupiter blocked out by the moon, an event called an occultation by astronomers today.
Jupiter is the 4th-brightest object in our sky, after the sun, moon and Venus. Seeing the moon pass in front of the planet – blotting it temporarily from the sky – would have been a fascinating and likely unlooked-for event around 120 BC.