There comes a moment early in Handel’s Messiah, where the first bass aria says it all about shadow and light. Backed by unison strings, the words “the people who wandered in darkness” meander melodically over the singer’s whole vocal range, each note like the blind leading the next blind note through an impossible depth of shadows. In a composition that is overflowing with musical tone painting, this moment stands out as paint-by-music—only to be eclipsed by the very next phrase: “They saw a great light.” With these words, the key changes from minor to major, the strings burst into full harmony, and the melody soars upwards. The moment is nothing short of luminous.
Giotto’s Adoration of the Magi. (Source: Wikimedia Commons)
It is also one of the most clever examples of doing double duty in music. The text, a citation from the Old Testament book of Isaiah, is understood by Christian theologians as a prophecy of the birth of Jesus, understood here as divine light. But coming in the Christmas section of Messiah, the great light also alludes to one of the most endearing parts of the Christmas story: The Star of Bethlehem, the wondrous star that in the New Testament settles over the birthplace of Jesus and guides the Magi to the infant. It is with this star that we concern ourselves here, fellow sky walkers.
That star of wonder. As I was growing up, the star always seemed central to me in our family Christmas celebration. Perched atop the tree, our glass star beaconed the holiday season, foretelling the visits from family, bearing, of course, gifts.
And so must the star of wonder have beaconed to the astronomically minded who have sought to explain its appearance through scientific fact. I will be upfront with you, fellow sky walkers: I find this pursuit to somewhat miss the point of Christmas. Nonetheless, it represents some remarkable tours de force in historical astronomy, so let’s begin.
The Magi
A key observation underlying all the astronomical accounts of the Star of Bethlehem rests with the identity of the Magi. It is now traditional to consider the Magi to have been kings, most notably in the carol “We Three Kings.” However, this interpretation did not arise until well after the historical time of Jesus, again by identifying Isaiah’s 800 B.C. prophecies of the Messiah with Christ. In fact, early Christian writing referred to the wise men as magoi, a Greek term derived from the ancient Persian word for Zoroastrian priests, hence wise men. It makes sense for the Magi to have been concerned with a star, as much of Zoroastrianism at that time involved astrological divination. So exactly what kind of stellar observation might have prompted the journey of the Magi?
A conjunction
One line of thinking involves reversing the course of the moons and planets to the years around 6 B.C. or so and looking for especially salient astronomical events. One explanation that comes in this guise is a conjunction of the planets. No less an authority than Johannes Kepler, the 17th-century astronomer, noted an alignment of Jupiter and Saturn in 7 B.C. More recent analyses focus on Jupiter-Venus alignments in 3 B.C. and 2 B.C. The star-gazing Magi would not likely have been fooled into thinking that two planets had merged into a star, but they may well have understood the event as an astrological omen. A similar argument applies to other visually salient cases of celestial mechanics, for instance occultations of Jupiter by the moon in 6 B.C.
Supernova or comet?
A different line of inquiry considers the possibility that the Star of Bethlehem was actually a supernova explosion that might have been observable in the Magi’s time as a new short-lived star. Arthur C. Clarke imagines this in his poignant science fiction story “The Star,” but there are actual historical references that might astronomically align with the Star of Bethlehem. Chinese and Korean texts from around 4 B.C. note what are now understood as several potential novas or supernovas.
Lastly is the possibility of a comet, which has long been part of the iconography of the Star of Bethlehem; the figure shows one such example by medieval painter Giotto. Those Chinese and Korean texts are in fact ambiguous as to whether the astronomical event they report was a star or a comet. A comet would have been of significant interest to the Magi, since comets were taken in those days to be astrological bad omens.
Tracking Leonard's Comet through the end of December 2021. CLICK TO ENLARGE
Leonard as seen through the eyepiece of a telescope. You need a scope or binoculars to see this view. To the naked eye, the comet appears smaller than the width of a finger at arm’s length. (Photos by Marc Vilain)
A comet for the 21st century
From our 21st-century standpoint, comets may no longer be bad omens, but they remain stars of wonder nonetheless. This is all a circuitous means of saying that we presently have in our skies a celestial Christmas gift in the form of Leonard’s comet, technically Comet C/2021 A1.
Until recent days, this comet has been a pre-dawn observation target, but it is now visible just after sunset in western skies, where it should remain observable until the end of December. Head to the Prospect Hill overlook and scan the horizon just after sunset. You will want a pair of binoculars, as this comet is not likely to be easily seen with the naked eye. You are looking for a small spot of fuzz, possibly with a hint of a tail. Do not expect the grandeur of Halley’s comet. To locate it, refer to the sky chart. It may also be helpful to use a planetarium app on your phone: You might need to use the technical designation C/2021 A1, as several comets bear the discovering astronomer Greg Leonard’s name. Also make sure that the app is up to date (as I found out the hard way).
If you don’t see the comet when you first go out, be patient and come back another day. Patience and waiting are part of the season of Advent, after all. The wait is worth it, as you can see from the photo, taken just this week at the Prospect Hill overlook. Note that it can be hard to spot fuzz upon fuzz, and our New England skies are more often than not fuzzy near the horizon. I spent more than one pre-dawn morning this past week, fruitlessly trying to parse cometary fuzz out of pre-dawn fuzz (it did not help that my planetarium app had a bug in how it calculates hyperbolic comet orbits, sending me to look in the wrong part of the sky).
May your holidays be filled with wonder, fellow sky walkers, whichever holidays you have made your own. And may your skies be filled with stars, all of which are wondrous.
Marc Vilain wanders the roads and fields of Harvard at night, to find wonder in the skies.
