Precession and Three Wise Men

It’s just a thought about a part of the Christmas story. There is the story about a star being just above Bethlehem around the time of the birth of Jesus. Why would that be significant and what star might that have been? It could have also been a comet.

A quick read of some of the internet sites about the Southern Cross reveals that the constellation is not visible in the northern hemisphere now (or at least from latitudes north of the Mediterranean), but that some of the stars were known by the ancient Greek astronomers around 400BC as part of the Centaur constellation. Due to precession of the earth the stars of the Southern Cross have slipped out of view below the horizon for people at these northern latitudes. The last time these stars were visible in the northern night sky was around the time of the birth of Christ about 2000 years ago, apparently.

What if some astronomers around the time of the birth of Christ wanted to see those stars that were known to be disappearing due to precession. They would have sought out some high vantage points and watched on the few days during the year when the relevant star rises and sets just above the horizon. From their high vantage point they would have noted landmarks above which the star would make a brief appearance. I don’t know about the topography near or north of Bethlehem but perhaps it was a convenient landmark for this stargazing.

It would be quite simple now with astronomical software to plot the stars as seen at particular places 2000 years ago. It would be easy to calculate which stars were disappearing and appearing due to precession from particular locations, as well as the rising and setting times for stars in transition. Perhaps a list of possible stars could be compiled. If the fabled star was part of the what we now call the Crux constellation that would be an interesting aside to the biblical story. I’d guess that if the star was part of the Southern Cross it might be Gacrux, but that is just a guess if there is anything to this idea at all. Another interesting thing would be to identify the vantage point from which Bethlehem is below that disappearing star. Is there an obvious place that would neatly line up these three points from 2000 years ago, and where would that be if there is such a place?

I suppose in those days there would have been a lot of cultural knowledge that would have been conveyed verbally. Only a relatively small social elite would have been literate and educated. Stories about astronomers/astrologers of the time might have been expressed in ways that lay people would have seen things and understood them. The story that wise men traveled from afar and who were watching for a star that hung above a particular town could perhaps be elaborated.

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26 Feb 2008

Some of the websites about Crux and precession mention that 2000 years ago the constellation was considered to be part of Centaurus at least with some of the cultures around the Mediterranean. It would be pretty obvious what part of the anatomy it would have been. I guess that might have added to some of the anxiety of having the relevant stars disappearing from the sky due to precession.