The Vatican Observatory astronomer and columnist Br Guy Consolmagno SJ has a fascinating piece at the UK Jesuit e-journal Thinking Faith about the star which the Magi followed.
Is there an astronomical explanation? Consolmagno's science makes him sceptical of Matthew's account; but his theology makes him ask questions too: if this is a pious story of Jesus being recognized by wise Gentiles, why have the Magi coming from the east, and not from Rome or Athens? And why were they astrologers, given that Jews did not approve of astrological forecasts?
I can only leave open the possibility that the story in Matthew is a parable with a message, but not a factual account of an actual astronomical event.
Of course, the other extreme is also possible. Maybe there was a totally miraculous star, zooming about the sky like a UFO, guiding three kings to the stable in Bethlehem.
I don’t particularly like this interpretation either, however. For one thing, it’s internally inconsistent. Why wouldn’t anyone in Jerusalem notice such a star?
And so on. It's fascinating, learned stuff. 
He considers the possibility of a supernova -- spectacular, unusual lights in the sky which appear perhaps once every 400 years. Or there are "wanderers" -- planets which change their position in the sky -- which have been considered by many astronomers over the ages.
The trick, though, is to find a solution that is consistent with the temporal setting of Matthew (probably in the spring, when shepherds would be out at night tending their flocks, in a year while Herod was still alive and king); consistent with the description of the ‘star’ (something to do with its rising); consistent with an explanation of how it would indicate the birth of a king, and how Judea would be indicated as the location of this birth; and consistent with the apparent fact that only astrologers were wise to this event.
My own personal favorite solution to these constraints is in Michael Molnar’s 2000 book, The Star of Bethlehem. He argues that there was a conjunction of all the planets and the new Moon, similar to that used by Augustus to support his own royal birth, occurring in the constellation Aries (which he argues is connected with Judea), in late March of 4 BC. Most appealing, this conjunction occurred when the planets rose with the Sun in the east – hence fitting the Matthew description, while explaining why only astrologers were aware of this event. They could calculate its occurrence, but no one, not even them, would actually see these planets: they’d be hidden in the glare of the rising Sun.
It’s all quite neat. And indeed it’s rather startling to realise that such an event really did occur in the sky about the time when Jesus may well have been born. If you have a planetarium program, you can look it up for yourself.
But was this really what Matthew was talking about? There’s hardly a consensus on this point.
And that's just as well, he concludes.
Because the real message is outside the realm of astronomical calculations. The events that draw each one of us to encounter our Saviour are rooted in our own lives, our own histories, our own belief systems. Every such set of events is inherently improbable. And thus, we each have our own unique story to tell of how we wound up worshiping at the manger.
