Attempts to seek an astronomical explanation for the Star of Bethlehem are in my view misguided. Relatively common events such as planetary conjunctions, comets or bright meteors would not have persuaded three wise men worthy of the name to stock up on gold, frankincense and myrrh and head west to Bethlehem in search of the Messiah, dropping in on King Herod en route. The people of the East were sophisticated astronomers who had in all probability been studying the heavens since prehistoric times, and they would have been aware that these things were nothing out of the ordinary.
More feasible is the idea that they saw a supernova - an event of the type that might only happen every few centuries. This idea formed the basis of Sir Arthur C. Clarke's classic short story The Star, about a Catholic priest who queried his faith when he realised the explosion had wiped out an alien civilization. More recently, American cosmologist Frank Tipler has suggested that a Type 1C hypernova - a stupendously powerful supernova - in the Andromeda Galaxy was what the Magi might have seen.
But even the supernova theory has one fatal flaw. The world at around 4 BC - the presumptive birth date of Christ - lay well within the realms of recorded history, and a supernova had it occurred would have been widely noted and recorded. But the Star of Bethlehem is attested only once, in the Gospel according to St Matthew (Matt 2: 1-12), which is believed to have actually been written by an anonymous Christian decades after the events it describes.
It is far more likely that that the reference to a star is no more than a metaphor, rather like the present-day usage of the word to describe notable actors, footballers, musicians, etc and that the "star" of Bethlehem is simply an allusion to Jesus rather than an astronomical phenomenon.
© Christopher Seddon 2008