The magi and the Star of Bethlehem (Dreamstime)

O Star of wonder, star of night
Star with royal beauty bright
As Christmas comes around in places where it's celebrated, folk are surrounded by the symbols of the Christian nativity blended with two thousand years of other traditions. It's the creche and the Christmas tree, candles and bells, Santa Claus and the three kings, snow and reindeer. But one of the most interesting to me is the Star of Bethlehem.

According to the Gospel of Matthew, after Jesus was born in Bethlehem, wise men came to Jerusalem asking "Where is the child who has been born king of the Jews? For we observed his star at its rising, and have come to pay him homage."

Opinions on the nature of the "star" range from those who believe it was an actual star of miraculous appearance to those who think it was created by Matthew to glorify the birth story. In between these two are many theories, including those that suggest there was an astronomical reality behind the appearance of the star.

Certainly, there was nothing that behaved like an ordinary star. Except for the Sun, stars are so far away from us that their positions seem to be fixed. They appear to move only as Earth turns and as it orbits the Sun. The stars maintain their relative positions and the movement is too slow for our eyes to follow it.

However the word "star" was not always as restricted as it is now. Everything heavenly was once considered some kind of star. Meteors were shooting stars, planets were wandering stars and comets were hairy stars. This broadens the possibilities.

We can start by eliminating bright fireballs (large meteors). They're pretty spectacular, but they don't last long.

Then we can eliminate bright planets like Venus or Jupiter. Although people these days might not recognize them, they were common sights to people without electric lights and aircraft. Obviously the star would have to be something unusual to get the attention of the wise men and set them off on a long journey.

A better possibility is a nova (short for stella nova, "new star"). These brighten suddenly (within a few days), making them appear to be new objects. They then remain visible for some time before fading again.

A nova isn't actually new. It's caused by the temporary resurrection of a medium-sized star that had run out of nuclear fuel and collapsed. These stars are called white dwarfs and are very dense, so over time their strong gravity can steal enough material from a companion star to set off a thermonuclear explosion. That's a nova.

Even more impressive than a nova is a supernova — the explosive collapse of a massive star at the end of its life. It's as bright as an entire galaxy and can remain visible for quite some time.

Either a nova or a supernova would be a fitting way to announce an important birth, but there are at least two big problems with both of them. Neither object would move around in the sky any more than an ordinary star. In addition, there is no record of any such occurrence during the period in which Jesus is thought to have been born.

But how about a comet? They do move over time and can be quite bright. They're also very dramatic and were thought to herald great events. Halley's Comet was seen seen in 11 BCE, but this is several years too early.

Other theories abandon the strictly astronomical for an astrological explanation. There are numerous suggestions for conjunctions of possible astrological significance. A conjunction is the appearance of at least two astronomical bodies close together. We can be verify these using planetarium software.

For example, there was a triple conjunction of Jupiter (the king planet) and Saturn in Pisces (astrologically associated with the Jews). The two planets came close together three times in a period of several months in a way that happens only every nine hundred years. Each of the conjunctions could have occurred at a significant point in the story: when the wise men — the Magi — began their journey in early summer, when they met Herod, and then as they were on their way to Bethlehem. However this occurred in 7 BCE and scholars consider this date too early.

A more spectacular conjunction was that of Jupiter and Venus around 2 BCE. The two bright planets came so close together that their discs overlapped, making it seem as if they had merged into one. Now that would be something worth seeing! Unfortunately for today's skywatchers, the next time they'll appear to be really close in the sky isn't until 2065. Though many lucky people with a clear sky saw such a conjunction of Jupiter and Saturn on December 21, 2020.

So what was the Star of Bethlehem? No one knows, but it has a spiritual power for Christians. And whatever you think and whether you celebrate Christmas or not, it's still a good time to join together in wishing for:

Peace on Earth, Good will to all.
Reference: Nick Stroebel on the Star of Bethlehem, https://www.astronomynotes.com/history/bethlehem-star.html