Astronomy – What was the Christmas star?

In St Matthew’s gospel, we are told about the bright Star of Bethlehem which led the wise men to the birthplace of Jesus where they left three gifts. This imagery has become one of the most recognisable features of Christmas around the world.

The Greek word, generally translated as ‘star’ (αστερα – astera/astra from which we get ‘astronomy’) has other meanings too. It can also mean planet, or could refer to other objects such as comets or meteorites. One thing is certain, St Matthew did not mention anything about the brightness of the star, or that it held any significance to anyone but the Magi.

So what possible explanations are there for this significant image of Christmas time?
Could the Magi have seen a supernova? A supernova is when a star explodes and often we can see the star dramatically increasing in brightness. Some of these supernovae are so bright that they can even be seen during the day.

Around the time of these events, the only people recording these celestial events in detail were the Chinese and Koreans. One such star was recorded by the Chinese in the spring of 5 BC, and was seen for more than two months. However, its position in the constellation Capricorn means that it is unlikely that it would have seemed to “lead” the wise men. It simply was in the wrong direction.

How about a comet? Again, we look to the records of the Chinese and two possible comets are listed. One in 5 BC and the other in 4 BC.

One advantage of the comet theory is that comets move across the sky. This could fit the interpretation of the gospel that the star ‘moved’ as it directed the Magi.

In most cultures, a comet was seen as an omen of death and destruction, so it is more likely that the Magi would have run from, rather than go towards such an omen.

Was it a conjunction of Jupiter and Saturn? Kepler put forward the idea that the star could be a close conjunction between Jupiter and Saturn. In rare circumstances the two would appear to form a single, bright star. Unfortunately there was no such conjunction in the relevant period in history.

Interestingly there was a conjunction of Jupiter with two other planets: Saturn and Mars in 5 BC, in the constellation of Pisces. However they would not have joined together as one big star. Rather they would have looked like the recent conjunction of Venus, Jupiter and Saturn we saw just a few weeks ago.

Falling stars look like they are moving. Could it have been one of them? Many artistic impressions of the Christmas story show the star looking like a meteor, or falling star. The problem is that meteors are very short lived, lasting just seconds. There is no way that the wise men could have followed one. Also, early astronomers or astrologers would have been very aware of things in the night sky and would certainly have recognised a meteor as nothing particularly out of the ordinary.

There are a number of candidates that could scientifically explain the Christmas star, however none of them are particularly strong. Barring some archaeological discovery to settle the question, the mystery of the Star of Bethlehem will remain in the realm of faith.
One thing we can all agree on is the message which is attached to this imagery of the Christmas star: “… on Earth peace, good will toward men.” (Luke 2:14).