December is the traditional month for the immensely-popular “Christmas Star” skyshows presented at planetariums around the world. In these, the various theories that have been put forth to explain it are examined, as we shall do here.
Two very important factors need to be kept in mind in looking for the source of the Christmas Star. One deals with an uncertainty in time — that of the actual date of the first Christmas, which scholars say may have occurred as early as 7 BC. The other is uncertainty in terminology. In those remote days, just about any bright object that attracted people’s attention in the night sky was apt to be called a “star.”
One easily dismissed theory is that the Christmas Star was a bright meteor — what astronomers call a fireball or bolide. As most of us know from experience, meteors are very fleeting, typically lasting only a matter of seconds. Even a bright one could hardly have led the Wise Men halfway across the Orient! A related suggestion is that it was a great comet — something like Hale-Bopp, seen worldwide in 1997. This is more likely, since these objects stay in the sky sometimes for many months or more. Also, their scimitar-like tails do indeed look like some cosmic finger pointing down at a particular spot on the horizon. And it so happens that a great comet actually did appear in the year 7 BC.
Another possibility is that the Star was a planetary conjunction — the coming together in the sky of two or more of the brighter planets. A number of these did occur during the period we’re considering, the most spectacular involving Mars, Jupiter and Saturn. But at no point did they approach each other close enough to appear as a single brilliant object. There’s also the fact that such objects move rather slowly in their orbits. The Wise Men watching the sky over a period of many weeks would surely have recognized them as the familiar planets and not have called such an obvious grouping a “star.”
Two other explanations remain for the Christmas Star. The first involves the enigmatic subject of unidentified flying objects or UFOs. Proponents of this theory cite the fact that the star led the Wise Men, finally stopping and hovering over the town of Bethlehem. Such behavior is very characteristic of many reported sightings of these strange lights. But here we need to keep in mind that the daily rotation of our planet causes all celestial objects to slowly move from east to west across the night sky.
The final theory of what the Christmas Star might have been is that of a supernova explosion, in which a supermassive star literally blows itself to smithereens. At their peak, supernovas become so bright that they cast shadows at night and can be seen in broad daylight! The search continues for historical and astronomical evidence that one of these extremely rare events actually did occur around the time of Christ’s birth. Should this be the true explanation for the Christmas Star, isn’t it ironic that nature used the spectacular death of a super-sun to announce the birth of what many consider to be the greatest King that ever lived?
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Guest post: This article originally appeared on the Edmund Scientific site, as part of their Sky Talk series. The article was written by James Mullaney, former assistant editor at Sky & Telescope and author of five books on stargazing. Edmund Scientific has graciously agreed to let us post these articles to provide additional resources for Earth Science and Astronomy educators.
