JUPITER. The name of the greatest god of Roman mythology. And the name of the largest planet of our solar system. Jupiter has been known from ages-old to the present as the King Planet. This greatest of planets is a “gas giant,” approximately eleven times the size of Earth and over 300 times more massive. It circles the Sun far beyond Earth, in an orbit of about twelve years duration. In ancient times, planets like Jupiter were considered “wandering stars.” Since humans have assigned kingly qualities to this giant wanderer for dozens of centuries, might it have something to do with our Star announcing the birth of a king? That will be our working theory.It’s not enough to have a kingly name and reputation, of course. To be Matthew’s Star, Jupiter as viewed from Earth would have to do peculiar things. More precisely, as considered by a magus viewing from the Middle East during the years 3 and 2 BC, Jupiter’s movements would have to satisfy all nine identifying characteristics of the Star. In September of 3 BC at the time of the Jewish New Year, Rosh ha-Shanah, Jupiter began to do just that.
A magus watching Jupiter that September saw two objects moving so close that they appeared to touch. This close approach of celestial bodies is sometimes called a ‘conjunction.’ Our Middle Eastern viewer saw Jupiter coming into a close conjunction with the star, Regulus. Regulus takes its name from the word root which yields our word ‘regal.’ The Babylonians called Regulus Sharu, which means ‘king.’ The Romans called Regulus Rex, which means ‘king.’ So to start things, at the beginning of the new Jewish year, the Planet of Kings met the Star of Kings.
This conjunction may have indicated kingship in a forceful way to a Babylonian magus (satisfying one qualification for the Star), but would it have startled him? Probably not.
Jupiter’s royal dance
Jupiter glides slowly past Regulus about every 12 years. Let’s assume our magus enjoyed a 50-year career, say from age 20 to age 70. We don’t know how old the Magi were, but if our man was in the second half of his career, he might have seen such a pass two or three times before. Jupiter’s orbit wobbles relative to Regulus, so not every conjunction is as close as the one he saw in 3 BC. Perhaps our magus recorded this event with some interest, but it is hard to imagine great excitement. Not from this alone. But, of course, there is more.
The planets move against the field of fixed stars. From Earth, they appear to be “active.” For example, were you to watch Jupiter each night for several weeks, you would see that it moves eastward through the starry field. Each night Jupiter rises in the east (satisfying a second Star qualification). Each night it appears to be slightly farther east in the field of fixed stars. All of the planets move like this.
But the wandering stars exhibit another, stranger motion. Periodically, they appear to reverse course and move backward through the other stars. This may seem odd, but the reason is simple enough: we watch the planets from a moving platform—Earth—hurtling around the Sun in its own orbit. When you pass a car on the freeway, it appears to go backward as it drops behind. For similar reasons, when the Earth in its orbit swings past another planet, that planet appears to move backward against the starry field. Astronomers call this optical effect retrograde motion.
In 3/2 BC, Jupiter’s retrograde wandering would have called for our magus’ full attention. After Jupiter and Regulus had their kingly encounter, Jupiter continued on its path through the star field. But then it entered retrograde. It “changed its mind” and headed back to Regulus for a second conjunction. After this second pass it reversed course again for yet a third rendezvous with Regulus, a triple conjunction. A triple pass like this is more rare. Over a period of months, our watching magus would have seen the Planet of Kings dance out a halo above the Star of Kings. A coronation.