It's hard to imagine Christmas without images of a giant star in the night sky over Bethlehem, with one supernaturally bright beam pointing toward a stable.

For carolers, the key words are in "We Three Kings of Orient Are" where everyone sings: "Star of wonder, star of light, star with royal beauty bright. Westward leading, still proceeding, guide us to thy perfect light."

"The Christmas carols are surprisingly accurate when it comes to the details of what we know" from scripture, said New Testament scholar Colin Nicholl of Coleraine, Northern Ireland. "In many cases where they fill gaps in the biblical narratives, they end up including material that is pretty sound -- at least based on my research."

The problem is that this heavenly object simply does not behave like a star. Thus, in his new book "The Great Christ Comet: Revealing the True Star of Bethlehem," Nicholl blends material from history and science to argue that this phenomenon can best be explained by charting the path of what he calls "undeniably the single greatest comet in recorded history."

The language familiar to most readers is found in Matthew's Gospel, which states: "Now when Jesus was born in Bethlehem of Judaea in the days of Herod the king, behold, there came wise men from the east to Jerusalem, saying, 'Where is he that is born King of the Jews?' for we have seen his star in the east, and are come to worship him."