On Friday this week, the waxing crescent Moon will sweep over the star gamma virginis in the constellation Virgo with Jupiter standing by, south of the Moon where the star Spica is at its back. This is a beautiful sight and it triggers one of the most famous legendary elements of Roman history.
The gamma star in Virgo is named Porrima, for a goddess of prophecy. Porrima was one of many types of female oracles that populated the ancient world, which included among them the sibyls.
Perhaps one of the most famous sibyls was the Cumaean Sibyl, not only because of the way Michelangelo painted her in an old and muscular form on the ceiling of the Sistine Chapel, but because of her role in rendering prophecy. The Cumaean Sibyl prophesied by “singing the fates” and writing on oak leaves. She would arrange these leaves inside the entrance of her cave, and if the wind blew and scattered them, she wouldn’t reassemble them to form the original prophecy again.
The sibyls' prophecies were recorded in the Sibylline Books. Legend holds that once, the Cumaean Sibyl offered nine of these books to the last king of Rome; he declined to purchase them, because she demanded too high a price, so she burned three and offered him the remaining six at the same price. He refused again, so she burned three more and repeated her offer. Finally the king relented and purchased the last three at the full original price and had them preserved in a vault in the temple of Jupiter.
Now when you look for this story in the sky this week, you’ll first see the Moon waxing through the front region of Virgo, like the cave of the Cumaean Sibyl, where she is singing her fates and preparing her prophecy. Then on Friday, an hour after sunset, the Moon will sweep over the star of the ancient goddess of prophecy, facing the planet Jupiter like the temple where the Sibylline books were kept.
In legend the temple was eventually burned down, and the oracular utterances contained in the books there were lost, so that they could only be known by those who could read the stars.