Star of wonder and of science

04 January 2019

Andrew Davison balances the astronomical explanations for the Star with its cosmic significance

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The Adoration of the Magi, led by a star: fresco by Giotto from the Scrovegni Chapel (completed 1305)

The Adoration of the Magi, led by a star: fresco by Giotto from the Scrovegni Chapel (completed 1305)

ASTRONOMERS — among them two luminaries of early modern astronomy, Tycho Brahe (1546-1601) and Johannes Kepler (1571-1630) — have had the Star of Bethlehem in their sights for some time. Indeed, even to translate St Matthew’s account, you need to decide whether there’s a hint of stargazing vocabulary in his Gospel. The Authorised Version (“We have seen his star in the east, and are come to worship him”) suggests not. In contrast, the NRSV gives us “We observed his star at its rising, which is favoured today.

To the modern eye, there are two distinctive aspects of Matthew’s account. On the one hand, the sky announces, informing the Magi of the birth of the King of the Jews. That is all they need to direct them to Jerusalem. Once there, Micah’s prophecy would suffice to send them on to Bethlehem.

At this point, however, the star plays its second part, as pathfinder: “There, ahead of them, went the star that they had seen at its rising, until it stopped over the place where the child was.”

Astronomically plausible contenders for what Matthew might be describing are varied, but they tend to fit better with the first aspect than the second.


SOME discussions — though not all — mention a meteor, but generally only to dismiss it. Meteors fall too often to be remarkable, and last only seconds. A comet is another possibility, popular with artists. Giotto’s depiction, among his frescoes for the Arena Chapel, in Padua, is particularly notable. Painted just into the 14th century, the inspiration is Halley’s Comet, which had appeared in October 1301. It is moving to see this artist, who was so instrumental in bringing the observation of nature and a new naturalism into Western art, recalling that event in paint.

A comet, however, is a poor contender for the story. The appearance of a comet — something new, and out of kilter within the otherwise ordered systems of the heavens — was associated with disaster.


A further possibility is the brief appearance of a “new” (previously invisible) star: a nova, or supernova. The former are more common, flaring up during the life-course of some two-star systems. Supernovae are far rarer, but entirely more spectacular. They are the final stage in certain sorts of star death, and convert mass into energy so rapidly that a single star, at its passing, can momentarily outshine a galaxy of maybe 400 billion stars.

Records from China suggest a nova in 5 BC, but of a relatively modest kind. (That, we should note, is in the right time-frame: the birth of Christ is probably best dated to about 7-2 BC.)

Within the Epiphany story, a nova-burst in the sky might fit the bill, lasting for a while before fading. As with a comet, however, this unexpected event would likely not be seen as propitious. Better to turn to our final, and favoured, contender for catching the ancient imagination (whether of Magi, or of Gospel-writer): a planetary conjunction.


THANKS to light pollution, few of us are in touch with the changing sky. If we were, we could distinguish two sorts of motion. The backdrop is composed of stars, which seem to pan across the sky over the course of an evening, as the earth rotates. (There are also some gentle changes over the cycle of a year.) Across that background move the planets the word derives from the Greek for “wanderer”. Their remarkably complicated courses are set by the interrelation of their orbits with ours.

Kepler was a lucky man: he was alive during a rare supernova, in 1604. The year before, however, he witnessed the conjunction of Jupiter and Saturn in the night sky (the Christmas night sky, no less), and that sent him to his calculations. He was able to determine that something similar had happened in 7 BC, and with spectacular effect, since those planets then drew near three times in rapid succession.

Another candidate for the wondrous sight, the following year, would have been the clustering of three planets: Jupiter, Saturn, and Mars. Both of these events happened in the constellation of Pisces (said to be associated, for reasons I cannot fathom, with Judaea and the Jews). If we want to tie Matthew’s story to an astronomical event, something like this seems to be the best candidate.

Planetary conjunctions — or novae, for that matter — perform what I called the star’s first task: tipping off the Magi that something was afoot. That would suffice to get them to Jerusalem, where Micah would point them to Bethlehem. What it might mean, however, for the star to perform the second task — to “go ahead of them”, or to “stop over the place where the child was” — is far less clear. On the planetary hypothesis, the best fit may be the pause of a planet, as it changes direction in the sky.


THIS is probably as far as we can go, and it may already be too far. The temptation to ask scientific questions of an ancient claim about the night sky is strong and obvious, but, in doing so, we risk anachronism. Neither Matthew nor his contemporaries thought in terms such as supernovae. Their purpose was theological.

On that front, at least two principal themes emerge. First, we see both that there was a message for those who would hear it, and that those who did included Gentile magicians from the ends of the earth. Matthew’s Gospel, which is considered the most “Jewish”, here seems to take up themes from Isaiah (for instance), with its interweaving of the particular and the universal; and the idea of one nation — even of one representative figure — as the hope for the whole world. In our days of happily constructive interfaith relations, we might think of the Magi as the patron saints of dialogue and recognition across traditions.

The second theme is creation responding to the incarnation of the Son of God as the pivotal event in earth’s history. Even if a nova is not the best candidate for the Star, there is an informative link to be made with the medieval Christmas carol whose refrain is “Nova! Nova!” A new thing has happened — radically, world-changingly new — and creation, even the unchanging heavens, is caught up in its own act of homage.


THE development of astronomy since the time of Copernicus, Kepler, and Galileo is indisputable and magnificent; but, if we approach the story too much in astronomical terms, we may diminish elements that Matthew, his first readers, and subsequent generations thought important. In particular, modern astronomy offers a story that unfolds, relentlessly, over billions of years.

Planetary conjunctions, we now know, are baked into the celestial mechanics of our solar system. That might suffice to tip off observant watchers (the first theological angle), but it offers little of creation’s responding to God’s new gift (the second).

If heavenly messages are all we look for in the story, the facts familiar to modern astronomy might still fit the bill. If, however, we want something more dynamic, with creation making its response to God’s work, we will be left wanting, and the astronomical explanation may simply look like a divine stage effect.


A PARALLEL approach to the darkened sky on Good Friday is even more crushing, reducing it to the somewhat brief and partial lunar eclipse (there can be no solar eclipse near the Passover) on Friday 3 April AD 33.


Better than that to have the sun occluded in horror for three whole hours, even if only in the story. Better to have creation recoil in horror at the crucifixion of God incarnate — even if only as literature — than to have celestial stage machinery grinding its billion-year course.

So, too, perhaps, with the Star of Bethlehem, although the choice is less stark. A planetary conjunction has poetry, but I would only reluctantly give up on a tale of the sky’s bursting into amazed and grateful light, as Christ grows within his mother’s womb. We may do better with the story as story than with the story as science.


Canon Andrew Davison is Starbridge Lecturer in Theology and Natural Sciences in the University of Cambridge, Fellow of Corpus Christi College, and the Canon Philosopher of St Albans Cathedral.

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