The following originally appeared in the News Review in 2009, and with a few updates, I thought it might be appropriate for the season again:
“... and, lo, the star which they saw in the East went before them, until it came and stood over where the young child was” (Matthew 2:9).
Thus, according to Christian gospel, were the Three Magi led to Bethlehem.
It’s a very nice story, but from a scientific perspective, there is a lot of disagreement over exactly what the Three Magi / Wise Men / Kings were following.
First, it’s unlikely that it was a star at all, as stars do not noticeably move or change brightness from day to day. That leaves the Moon (too common), supernova (exploding stars), comets or planets. Venus, in particular, is bright and can move noticeably over a few weeks.
The computer I’m writing this article on has a planetarium program that can show me exactly what the sky looks like, from any place in the world, on any given date. The location is easy: I just type in ‘Bethlehem’. However, the year is not so straightforward; all we know is that it had to be before King Herod died, somewhere around 4 BC. Throw in the differences between our current Gregorian calendar and the Roman and Julian calendars of the time, and nailing this down to a decade, much less a month, is a guess at best.
If one cycles through the astronomical events a few years prior to Herod’s demise, there was a supernova in 5 BC, an appearance by Halley’s Comet in 12 BC, and a whole lot of planetary conjunctions in between, any one of which would have looked pretty good to a people waiting for the Messiah to come. But, without a date, it could have been anything.
Skip ahead two thousand years to this Christmas. The Moon is full on Christmas Day for the first time in almost 40 years, kind of unusual. Mercury makes a brief appearance on the western horizon, setting an hour after the Sun; Jupiter’s up by midnight and Comet Catalina by 2:15 a.m. All nice, but certainly nothing that might inspire three supposedly ‘wise’ men to journey anywhere.
We will probably never know the inspiration for the Christmas Star, but does it matter, really? Sometimes a narrative is so good that details would just spoil it. Besides, those who enjoy spending evenings looking up at the heavens do not need a special event. What the universe offers up in your own backyard, every night of the year, is inspiration enough.
Merry Christmas.
