British Museum

Poor Balthassar’s almanac. This ancient Babylonian astronomical text, dating to 8 B.C.E., was written in wedge-shaped cuneiform script impressed into a clay tablet. The text details the movements of the moon and the planets over the course of the upcoming 13 months—the year 7/6 B.C.E.—and indicates that the celestial bodies would be following some unusual paths. Particularly, the tablet shows that Jupiter and Saturn would remain together in the constellation Pisces for 11 months, coming into close conjunction three times.

The tablet describes the end of the conjunction as follows: “Month 10 [called Tebet], the 1st of which [December 23] will follow the 29th of the previous month. Jupiter and Saturn in Pisces, Venus in Scorpio, Mars in Aquarius. On the 5th, solstice. On the 10th, Venus will reach Sagittarius…On the 15th, moonset after sunrise. On the 26th, Mars will reach Pisces.”

While only a single copy remains of most ancient Babylonian astronomy tablets, the almanac for 7/6 B.C.E. is known from four copies (including this copy in the British Museum)—an indication that ancient scribes and astronomers recognized the rare and exciting nature of a triple conjunction, which occurs only once every 800 years.