The Christmas Star

by Paul Downing

AS
you might have noticed it is almost Christmas. I thought it might be good to
reflect on that famous celestial event that has been so much reported: the
Christmas Star, which is said to have guided the Wise Men to the infant Jesus. Much
thought has been given to the possible causes of this bright object. The main candidates are:

* A passing comet

* A supernova (a star which explodes
with devastating force and brilliance)

* A conjunction of bright planets (Jupiter
and Venus are both bright enough)

As
far as historians have been able to work out, the actual timing of Jesus’ birth
was between 3 – 7BC and most likely in the month of September. Interestingly, when we look backwards in time
we can see several exciting astronomical events took place during that period. Two
comets were reported by Chinese astronomers, in 4BC and 5BC, but in those days
comets were always associated with disasters and so it is felt unlikely that
this would be our answer. There was indeed a supernova, visible for two months
in March and April of 5BC. Although this is a possibility, supernovae do not
move as the Christmas Star is supposed to have moved. This leaves us with a
planetary conjunction, which is when two bright planets appear close to each
other in the sky. Amazingly, by tracing the planetary orbits backwards we can
show that there was a very close conjunction of Jupiter and Saturn on June 17, 2BC.
Indeed they were so close together that they appeared to merge into one very
bright object with part of it moving from night to night as they moved apart
again. In all the time I have been an astronomer I have never witnessed such a
close conjunction, and it must have been a quite spectacular event. Maybe this
was the Star of Bethlehem. We will never know the truth of course, and there
remains the possibility it was a truly divine event, with no Earthly
explanation. Whatever the truth, I send you and your families my very best
wishes as you celebrate your Christmas.

This article was printed in December 2006

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