Born under a wandering star

Owen Gingerich ponders astrology and Christ's premature birth.

On a bleak, mile-high peak towering above the headwaters of the Euphrates stands the impressive mortuary monument of Antiochus I, a Greek-speaking monarch of the first

century BC. Among the huge heads and bas-reliefs on Nemrud Dagh, one slab is particularly intriguing. Bearing a star-studded lion with a crescent moon on its breast and three labelled planets above its back, the stele proves to be an astronomically datable configuration, corresponding to July 7, 62 BC, Mars, Mercury and Jupiter in conjunction provided a favourable omen for King Antiochus's coronation.

While such a stone horoscope is essentially unique, other artefacts, especially coins from the first century BC, also point to a strong cultural interest in planetary astrology. It was a series of coins from Antioch, bearing a moon, a star (planet) and the zodiacal constellation Aries, that triggered Michael Molnar's curiosity about the symbolism involved. A numismatist and an astronomer, he launched an investigation that brought him into what George Sarton, the positivist father of modern history of science, once called "a wretched subject", namely, early astrology. And from there the trail led to a fresh interpretation of the "star" of the magi.

A small ocean of ink has already been spilled in attempts to identify the Star of Bethlehem. Most look for a conspicuous omen, a supernova, perhaps, or a bright comet, or an arresting planetary conjunction. But the astrologers from the East saw a sign not so apparent to the denizens of Judea or to King Herod's court, and thus surely something less obvious and more arcane was involved. Yet, if the biblical story is historically sound,there was a portent so compelling as to force the wise men on a journey to verify their conjectures.

Hypotheses with astrological overtones have been on the table for several centuries. In 1604 Johannes Kepler suggested that the great conjunction of Jupiter and Saturn in Pisces in 5 BC, could have ignited a nova to become the magi's star. Close approaches or conjunctions of Jupiter and Saturn are common enough, coming just about every 20 years. But Kepler's was no ordinary conjunction: it was the first conjunction in many centuries to fall near a fiery zodiacal sign. As the immediate forerunner of the 800-year cycle of conjunctions that took place in successive 200-year sequences in the fiery, earthy, airy, and watery signs of the zodiac, it could perhaps have produced a new star. After all, Kepler had witnessed precisely such a phenomenon under similar circumstances in October 1604, when the last well-observed galactic supernova blazed forth within a degree or two of the conjoined planets. Armed with this information, Kepler went to work with chronology to show that, paradoxically, Jesus was born several years BC.

Today's commentators have dropped the untenable notion of a conjunction triggering a supernova, but many have concentrated on the so-called "triple conjunction" in Pisces in 7 BC, where faster-moving Jupiter bypassed Saturn, then retrograded past a second close approach, before conjuncting once more in its normal forward motion. This has set interpreters to work to understand why Pisces would be seen as a constellation particularly pointing to Judea.

That is all a big mistake, Molnar has concluded, especially since early Greek astrologers are practically unanimous and specific in assigning the role to Aries. And the sign of Aries on the Antiochan coins signifies the annexation of Judea, which took place around 6 BC. Intrigued by these and other ancient coins, Molnar set out to find how various astrological motifs acted as credentials for the rulers minting the money, a task that led to an examination of what elements were seen as favourable portents for regal horoscopes.

Ultimately Molnar discovered that April 17, 6 BC offered a close arrangement of planets in and near Aries that would, to the perceptive eye of an astrologer, signify "incredible regal conditions" for the birth of a king in Judea. Regal Jupiter was so closely conjoined to the Moon that it was in fact occulted by it for an hour or so. The Sun was also in Aries, the sign of its so-called exaltation, while Venus in nearby Pisces was also in its sign of exaltation. Saturn and Jupiter rose before the Sun, a textbook example of "regal attendance", while Mars and Mercury followed the Moon, satisfying the lunar attendance criterion. Not easily visible by eye because of the proximity of the Sun, the configuration could be calculated by knowledgeable astrologers. "The excitement of the magi is now understandable," Molnar writes, and quotes Matthew's account: "When they saw the star, they rejoiced with exceeding great joy." Furthermore, the Greek words of Matthew's gospel are loaded with expressions that have technical astrological significance - "went before" and "stood over" described what Jupiter was doing "in the east" (in the ascendant).

Having read innumerable Christmas star accounts over the years, I find Molnar's carefully situated analysis particularly compelling, surely one of the most cogent presentations of our century. It makes good sense in the cultural context of its time, and lends credibility to the historical authenticity of the story of the magi coming to Jerusalem in search of a new-born king. There is, of course, no independent evidence that the astrologers from the East actually located the baby Jesus. That part of the tradition could be a midrash , an instructive juxtaposition of various memories to form a story of meaningful moral import. Molnar seems persuaded that Jesus was actually born on April 17, 6 BC, but his interpretation does not rise or fall with this detail.

The apostle Paul railed against the contemporary idolatry of astrology when he warned the Ephesians "against the cosmic powers, against the authorities and potentates of this dark world, against the superhuman forces of evil in the heavens"; it would actually weaken my faith in 20th-century Christianity to believe that Christ was born on an astrologically chosen day. Nevertheless, for an ancient world accustomed to signs and wonders, such a packaging of the circumstances of Christ's birth could have made excellent strategic sense, like American presidential candidates being born in log cabins. In any event, the chronologers do agree that Jesus was born a few years BC - so those who wish to celebrate the 2,000th anniversary of Christ's birth in the very year have already missed the occasion.

Owen Gingerich is an astronomer and historian of science at the Harvard-Smithsonian Centre for Astrophysics in Cambridge, Massachusetts, United States.