Comet of Bethlehem

Look above the manager roof in this scene from Italian Renaissance master Giotto di Bondone’s _Adoration of the Magi_. The “star” that Giotto painted had been famous for centuries as the one featured in the Gospel of Matthew which inspired the wise men to travel to King Herod of Judea to inquire about the prophecy of the Jewish Messiah in Bethlehem. But a closer inspection reveals that Giotto’s “star” looks more like a comet. And probably, the artist — who favored painting from his own observations — had a certain comet in mind.

Comets orbit the sun, and are partially made up of ices that change directly into gas when they get close enough, forming a “coma” around the central nucleus which is the small solid center. These glasses mix with dust particles to form a tail that flows away from the sun. (There is also something called an ion tail which has less mass and therefore goes in a straight line, as opposed to the dust tail’s curved trajectory.). Giotto’s celestial body has both.

In fact, Halley’s comet did appear in Europe in 1301, and many historians believe that Giotto’s work comes from his memories of that. However, an interesting article by D.W. Hughes, K.K.C. Yau, and F.R. Stephenson in the _Journal of the Royal Astronomical Society_ argues that Giotto, since he was making his frescos of the Birth of Jesus in 1304, might have been a comet seen in that year.

Regardless, throughout much of Western European history, comets were thought to be dire symbols of doom. According to Aristotle et al., the things on earth were subject to change, but the more perfect heavens were predictable — comets destabilized this vision. Giotto’s comet/Star of Bethlehem might have had both the happy prognostication of Jesus’ birth and the dreadful forewarning of King Herod’s “massacre of the innocents” (In the Gospel, the king demands the killing of all male infants under two in order to prevent the rising of a future rival to his power.)