Around this time of year, astronomers are often asked “What was the star of Bethlehem, exactly?”. It’s a difficult question, because we have so little information to go on, and what we have precludes most any possible scientific explanation. Still, it might be fun to look at some of the most popular ideas, and seeing what holes we can find in them.
The story of the magi (or Wise Men) is told in the first twelve verses of Matthew chapter 2 and goes something like this: The magi arrive in Jerusalem, from the East, trying to find the King of the Jews – they saw his star rising in the East and have come to worship. The chief priests and teachers tell them of a prophecy by Micah that a great ruler will be born in Bethlehem. The magi head out to Bethlehem (which was about ten kilometers south, two hours by foot), and find that the star is guiding them and eventually stops above the birthplace of Jesus (I’ve left out the political intrigues and machinations of King Herod, since we’re investigating astronomy, not infanticide).
So, to explain exactly what the Star of Bethlehem was, we need to find a natural phenomenon which meets these characteristics: It was visible for long enough that the Magi were able to travel from their home country (usually assumed to be Persia) to Jerusalem, and have time to make inquiries around Jerusalem before being ushered into audience with King Herod. For about 2 hours it moved visibly, directing the magi precisely to a specific location, and finally it stopped moving directly above the stable where Jesus was born.
The most common theories are that the Star was a comet, a planetary conjunction, a very bright meteor, a nova, or a supernova.
The first two have a common problem – they are both the sort of things that astrologers are interested in. However the bible, and Jewish law in general, has always been very much against astrology. It seems unlikely that God would use astrological signs to tell people about the birth of the Christ, and that Matthew would so happily record it as proof of Jesus’s divinity! But there’s more wrong than just that. A comet was universally seen as a BAD omen – the death of a king, for example. The magi were looking for a birth, not a death.
A planetary conjunction, however, could mean anything – astrology back then was even more disorganised and contradictory than it is now with practitioners frequently seeming to just invent their own interpretations of signs as they pleased. Even so, a conjunction (When two or more objects in the sky move very close to each other) does not match the description given. First of all, it does not appear as “A star”, and secondly, they don’t last long enough – anything from a few days to a few weeks.
Novae and Supernovae are two very different things, but appear similar in some ways. In both cases, a new star appears in the sky for a period, and then fades away. A supernova is usually vastly brighter than a nova – some notable supernovae have been visible during daylight, and cast shadows at night – although if it is far away it might not appear that bright to us at all. But these objects also have the problem of duration – How long does it take to travel by foot (or even camel) from Persia to Jerusalem?
Finally we have the bright meteor. These never last more than a few seconds, since they are objects travelling at many tens of thousands of kilometers per hour smashing through the atmosphere. A meteor could match what many of us imagine as a Star of Bethlehem, but not what is described in the Bible.
There is one detail that we have to look at separately. The Christmas star shone for an extended time in the East, and the magi somehow knew to travel West to Jerusalem. Once there, the same star guided them directly to the birthplace – it was moving. Finally, it stopped moving directly above the birthplace. This was no astronomical object, if they were able to tell what building it was above! In fact, there is no natural phenomenon which behaves in this way.
Conclusions, then? That depends on whether you consider the Bible to be the inviolate word of God, or just an interesting collection of religious mythology. If you’re a skeptic, then you can write the whole thing off as fiction, or a mutation of many related Birth-Of-A-King legends that were popular in ancient times, especially since there are no other records (not even in the other 3 Gospels) of the Star of Bethlehem. And if you are a Christian, then you accept it as a supernatural miraculous event – God made a light in the sky which led the magi. It wasn’t a natural event, it wasn’t a star or a comet or any of the other popular ideas.
In the end, we apply the words of a wise man: Faith does not require evidence, and Evidence does not require faith. There’s not enough evidence to prove that there even was a star, and it is ultimately our own decision whether to apply Faith or Evidence.
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