The doors of the temple of Janus were closed for only the third time in Roman history. And all went to be enrolled, each to his own city. This enrollment, described in the Gospel of Luke, which brought Joseph and Mary to Bethlehem, always has been a mystery since no regular taxation census occurred at this time. Novae have been suggested, the unexpected, sudden brightening of a star from invisibility into a bright object for a period of days or weeks. There is no historical record of such a nova, nor is it clear what a nova's astrological significance would be.
Comets are candidates, for they appear sporadically, move, and even seem to point down to the earth.
Meteors and fireballs are even less likely candidates. Conjunctions of planets have long been considered good possibilities. A conjunction is a close apparent approach between two celestial objects. The closer the objects, the more visually impressive is the event and the more significant astro- logically. In 3 B.C. and 2 B.C., there was a series of close conjunctions involving Jupiter, the planet that represented kingship, coronations, and the birth of kings.