. . .which is driving me to distraction. As far as I remember, the story concerned a group of scientists investigating a long-dead civilization on a planet that had been burnt by a star going nova. The scientists finally find a dead machine that had been marking the years since the end of the civilization, and they figured out that the nova would have been visible on earth over Bethlehem in A.D. 0. Does that ring bells with anyone? Thanks in advance.