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Column What was the Christmas Star?

According to the Bible story, the Star of Bethlehem – or the Christmas Star – led the Three Wise men to the birth of Jesus 2,000 years ago. But was it an actual astronomic event?

HOW DOES ASTRONOMY relate to the Christmas Star? Whether or not the story described in the Bible actually happened, there is a some relevant astronomy when taken in context of the Middle East two thousand years ago, so it’s not surprising that astronomical events would have inspired or influenced writings or events at the time.

The Biblical Magi, or the Wise Men, were likely to be people well-versed in astronomy. In their time, astronomical events would have been believed to be signs and predictions about events on Earth. This was what we would now call astrology. The Middle East region was historically renowned for its advances in science and mathematics, so the appearance of astronomer-priests in the story of the Christmas Star strengthens the idea that, if it happened, it was something celestial. There are a number of possibilities that would explain the Christmas Star that took place approximately two thousand years ago.

An occultation

Five years ago, at the start of December 2008 as the Christmas season was underway, there was an incredible astronomical event that astounded people who saw it. In the early evening, as a thin crescent Moon hovered over the horizon, a brilliant glowing ‘star’ appeared from behind it, slowly moving away from the arc of the Moon.

Throughout that evening I received countless calls from people asking what was happening to the Moon. Was our nearest celestial neighbour breaking apart? Was it aliens? Was it the Christmas Star coming back?

The astronomical event in question was the end of an occultation, where one object in the sky is obscured – or occulted – by another. In this case, the two objects were the Moon and the bright planet Venus. The Moon and Venus are often placed close together for a couple of days each month when Venus is in the sky (indeed, Venus is in our evening skies now and you may have spotted a close conjunction), but occultations of such spectacle are a much rarer occurrence.

In 6BC two occultations took place. Similar to the occultation of Venus in 2008, Jupiter was twice obscured by the Moon in the constellation Aries. When we consider the astrological significance of Aries and Jupiter at the time, we find ourselves at a possible contender for the Christmas Star: Aries was the ‘ruling starsign’ of Judea, while Jupiter was the ‘star of kings’. Combining these, and remembering that Jupiter appeared from behind the Moon, we now have an astronomical event that may have signified a birth of a Jewish king.

Comets always ‘point’ towards the Sun

Of course, there are events that may have occurred that were a little less esoteric, and were more actual astronomy rather than observations blended with astrology and mysticism. One such celestial event may have been the appearance of a comet. While we didn’t get to see Comet ISON as well as we hoped, anyone who has ever seen one (or even a photo of one) will know what they look like. In one sense, they almost resemble an arrow pointing in a certain direction. Comets always ‘point’ towards the Sun, so if a comet was visible in early morning before sunrise, it would have pointed east, which is the direction the Three Wise Men are said to have travelled.

As well as this, comets move through the sky, and are in a different place each night with respect to the background stars. As such, over the space of days or weeks, the movement of the comet could have acted as a guide for the travellers.

Halley’s Comet orbits the Sun every 75-76 years, and we know that it was visible from Earth in 12BC. The appearance of the comet was noted by Chinese astronomers at the time, but they didn’t report a particularly spectacular display from the object.

Did a ‘new star’ influence the Biblical story?

Another object recorded by the Chinese astronomers was the appearance of a nova – or ‘new star’ – in the sky in 5BC. A nova occurs when a small, white dwarf star pulls hydrogen gas from a nearby companion star. The gas falls to the surface of the white dwarf where it becomes intensely hot, and finally reignites and undergoes nuclear fusion. The result is an explosion of light and heat.

While most nova events are very far away and too faint to see without telescopes, the explosion was seen easily by the astronomers in China and was reported to have stayed in the sky for two months. Maybe this event influenced the Biblical story.

So, what was the Christmas Star that features in the Bible? It’s a good question, and certainly from an astronomical perspective, it could have been any of a number of celestial events. There are several theories as to what it could have been, but I don’t think we’ll ever really know for sure!

Conor Farrell is an avid science enthusiast and studied physics with astronomy at Dublin City University. He now works with Astronomy Ireland to promote all things space-related to a wider audience. In his spare time he writes about science and current affairs, and can be followed on Twitter at @conorsthoughts.

Read more of Conor’s columns here.

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