Pastor Max Solbrekken shares this theory at his website http://www.mswm.org/seasonal/real_star.htm (link found to be inactive 1-14-00) where he also discusses other aspects of Christmas. Here's an excerpt:
Canadian Press (CP) carried a story – some years ago – called ‘Yule Star Called a Comet’, quoting astrophysicist Paul Feldman. The National Research Council scientist told the Royal Astronomical Society in Ottawa that Chinese records for March of 5 B.C. mention a “broom star” that could have been easily seen by the Magi coming from Persia.
He said that the comet traveled eastward for about 35 days, which would have given the Magi ample time to travel the 1,100 miles to Jerusalem. The comet would have been obscured by the sun and invisible to the human eye.
When they reached Jerusalem and consulted with Herod and were told of the Biblical prophecy concerning Messiah’s birth in Bethlehem, they made the 5.5 mile trip. By then, the comet would be visible from the west and seen to be pointing towards Bethlehem.
Feldman states that Matthew was the only gospel writer to mention the star because he was a “civil servant – an educated man who had access to government records. The other gospel writers were uneducated fishermen”.
He further states, “And the Gospel according to Luke confirms that Jesus was born in the spring of the year. Luke says the shepherds were watching their flocks at night and the only time that is done is during lambing, which happens at the time of year the comet was reported.”
Astronomer Nick Strobel comments as follows on this theory on his page about the Christmas Star http://rampages.onramp.net/~binder/Xmastar.html
The new star could have been a comet, something we now know to be much different than a nova, but long ago comets, like novae, were regarded as heralding important events (though comets usually portended something bad!). Because of the broom-like appearance of comet tails, the Chinese associated comets with ``sweeping away the old order of things.'' The wise men originally saw the Bethlehem Star in the east and by the time they set out for Bethlehem after visiting King Herod in Jerusalem, they could have seen it in front of them as they headed south. A comet could have traveled from east to south during the 2--4 month journey of the wise men. However, the Chinese did not record any motion of the object. Comet Halley did make an appearance around that time, but its appearance in 12 B.C.E. is well outside the probable timeframe for the birth of Jesus.