i've heard that it wasn't a star so much as an astrological sign (since the "wise men" were probably persian zoroastrians--special note, the word used for them is the same use to describe sorcerers in the rest of the bible). this sign was a clear reference to the people of israel and thus directed them to it. and um. a star or any such body of light coming to rest on a stable is just silly.
anyways. the sign was probably the end of the reign of taurus. this is the same sign described in mithraist mysteries, hence the discussions i've tried to initiate before about the similarities of christianity and mithraism.