If the sky is clear over the next few days, but especially on Monday, we will have a chance to see an astronomical phenomenon that may have been the same one that inspired the journey of the Magi two millennia ago.

The two largest planets in our solar system, the gas giants Jupiter and Saturn, will cross paths in the night sky, appearing as a "double planet".

The event is called a conjunction. They are not rare in themselves, but one this close only happens around every 800 years, and timings suggest its appearance could have led it to become known as the Star of Wonder.

This is not a new theory. It was put forward in the early 17th century by the German astronomer and mathematician, Johannes Kepler.

Other possibilities are an exploding star called a nova or supernova. However, there is no Western record of such an event. Chinese records only have one possible mention that could connect to the time of the birth of Jesus.

Another candidate is a comet. One advantage of this notion is that comets move across the sky. It was argued that this fits the interpretation of the Gospel that the star 'moved' as it guided the Magi, and many classical pictures of the Nativity present the Christmas star as a comet.

The conjunction we are about to witness is a strong contender, although the two planets, even though close, will not appear to be one single heavenly body. But perhaps that doesn't matter - in the distant past a never before seen event like this would have had deep significance.

Whatever, we have to try to imagine ourselves into the minds of ancestors who took celestial events much more seriously than we do and strived to interpret them.

If the weather is kind and the sky is not overcast, Jupiter and Saturn will appear in the southwest sky, just above the horizon shortly after sunset. They will be visible to the naked eye, but binoculars could well enhance your viewing pleasure.