Several sites I visited today had links to various astronomical theories on the Star of Bethlehem, thus in the spirit of the season, I give you the links:

The Star of Bethlehem by Colin Humphreys, originally printed in Science and Christian Belief , Vol 5, (October 1995): 83-101 - Humphreys advances the theory of a planetary conjunction of Jupiter & Saturn or a comet.

Revealing the Star of Bethlehem by Michael Molnar - Molnar's website has a Q&A about his book on Jupiter as the Star of Bethlehem

What was the Star of Bethlehem? by Nigel Henbest in First Science - Henbest summarizes all the major astronomical possibilities for the Star.

Understanding the Christmas Star by Stephen Milton - Also a summary, but with more Bible exegises in combination with reviewing Molnar.

Happy reading!