January 6 is the day traditionally kept by Christian Churches for telling the story of how wise men from the East came to honour the baby Jesus. It’s also when Christmas decorations are taken down because it is “twelfth night”.

The Bible tells us that the wise men followed a star, which stopped over the place where Jesus lay. Did it really happen? Can science explain what such a star could have been? It has become a Christmas tradition that each year, astronomers find themselves answering that question for TV, radio, and blogs!

The short answer is that there are many ideas, but no certainty. Some Bible scholars question whether the stories of the infancy of Jesus are meant to be read as history. Perhaps they were written as symbolic stories – meant to intensify the message that Jesus of Nazareth was God’s Son, a great high priest, and the one who would save the world from sin by his death. On the other hand, if Matthew’s Gospel is giving us an accurate record of what wise visitors from the East actually said, perhaps the star was a miraculous vision given only to them and not seen by anyone else. If that’s true, then astronomy cannot help us.

 But let’s suppose Matthew’s account is accurate, and there was an object in the sky visible to the whole world as well as the travelling wise men. (The Bible doesn’t call them Kings, nor say there were three of them – only that they brought three gifts.) If so, what could the “star” have been?

 Chinese astronomers were meticulous in keeping astronomical records centuries before the birth date of Jesus. If there had been a dramatic new shining object in the heavens – a comet or an exploding star – we can be confident it would appear in their registers. But nothing suitable was seen in the years around the birth of the Christ-child.

 Matthew’s Gospel says that the star appeared to “stop” over the place where the baby lay. It’s probably not trying to describe an orb flying through earth’s atmosphere and hanging 30 feet above the manager. (Anything at the altitude would be far too earthly for astronomy to deal with!) The only thing which astronomers could see visibly moving (before human beings started launching satellites into orbit) are metors – “shooting stars” – which burn up in seconds and could not have led wise men on a journey of weeks or months.

The other sense in which an object can “stop” in the heavens is if it is something which normally moves, but travels very slowly compared to the fixed background of stars. Planets do this, and it’s only wise men and astronomers who have the patience to notice it. The closer a planet is to the Sun, the faster it orbits the Sun, and every so often, those planets further from the Sun than our own Earth get overtaken by our planet’s motion. When that happens, the planet’s position (compared to the stars) seems to pause, move backwards, pause, and start moving on its usual course again. In the period from 7 BC to 3 BC, Jupiter, Saturn and Mars all came close together in the sky (a rare occurrence) and then, some months later, Jupiter appeared to pause in its tracks – the double sign which could prompt the wise men to set out on a journey and then allow the star to “stop” when they got there.

Using the laws of gravity and motion, we can calculate the exact dates when these things happened. There is some doubt among historians about the year in which King Herod died, so it remains unclear whether the wise men could have seen Jupiter behave in this way and visit King Herod in the sequence the Bible describes. The Star of Bethlehem remains enigmatic – and that is perhaps best for any sign in the Bible, which is a more powerful sign if it keeps inviting us to ponder its true meaning.

Meanwhile, the wise men worshipped the Christ Child and, with no star to guide them, returned home to their daily lives. As we take down the Christmas decorations and return to our cycle of work, we have no star to follow, but the memory of the Christmas message of new life and good will to all people, to take with us through the year.

A Happy New Year to you all.

 This blog article was written by Associate Chaplain, Revd Dr Gareth Leyshon, whose PhD is in Astrophysics.