Many exegetes say—and I think they may have it right—that somewhere around the time Jesus was born (i.e., at the end of the reign of Herod the Great), there occurred some strange meteorological phenomenon that stuck in the minds of the people. Later, after Jesus’ death and they firmly believed that he had risen, when there arose a need for propaganda of the Christian faith through writings about the life, words, and deeds of Jesus’ life (i.e., the Gospels), the people remembered this phenomenon in the sky and understood it as a heavenly sign of the birth of Jesus.
What could this phenomenon have been? Three scientific explanations have been offered: (1) a supernova that appeared in the final days of Herod’s life; (2) a comet; or (3) a combination of stars shining especially bright in the sky. A closer consideration will serve us well.
The first view is the appearance of a supernova. A supernova is a gigantic star, much larger than the sun, that exploded millions of years ago at the end of its life and produced an immense light that, after thousands of years of traveling through space, finally reaches the expanse visible from earth. This is how Kepler in the seventeenth century explained the star of Bethlehem. The downside to this theory, though, is there no historical record to indicate such a phenomenon, which means we cannot prove it actually occurred.
The second view is the appearance of a comet. It is well known that comets are either remnants of a planet or star, a set of gas and dust that glow in the sunlight as it approaches the ground, or combination of the two. There are records for the famous Halley's comet, which is visible from earth every seventy-seven years, in Europe, China, and Japan since around 240 B.C. According to Chinese records, preserved to this day, the Halley’s comet was visible from earth in 12 or 11 B.C., during the reign of Herod and near the end of his life. Many astronomers believe that this was the event, lingering in the memory of the people, that was linked by Christians to the Savior’s birth. Brown believes it is possible that Halley's comet appeared in 12 B.C., some foreign ambassadors then came two years later to the court of King Herod to congratulate him on the completion of the large port at Caesarea Maritime and the remodeling of the city. He believes these events were combined by Christians prior to Matthew’s account of the star and the magi. Matthew did nothing more than just collecting all this information and giving some structure to a Christian legend that was already in existence.
Other researchers have proposed the conjunction of Jupiter and Saturn (known as a double conjunction), which happens every thirty years, along with Mars (known as a triple conjunction). The triple conjunction occurs every 257 years. This astronomical phenomenon is mentioned in texts as old as Sumerian-Akkadian cuneiform texts of the second millennium B.C. Calculations have been made and it is assumed that this occurred precisely in 7 B.C. and that this might be the “star” of the magi. I once directed a thesis at the Universidad Complutense in Madrid that defended this position. The author argued that the phenomenon was applied to Jesus by the community behind the Gospel of Matthew. That dissertation, by the way, was written by José Gómez Galán, “El nacimiento de Jesús de Nazaret. Historia y cronología.” He defended his dissertation at the Universidad Complutense de Madrid on April 24, 1998.
I am pretty skeptical about all of these theories. In my opinion, I think it is just implausible that a star appears and disappears, guides exotic characters from one place to another, and then perches above a house. Popular thought back then had signs in the sky announcing the births of significant individuals. The imagination is a powerful tool, and the Gospels, which are presented as historical works, are, more than anything else, propaganda that, in good faith, put into use popular legends in order to serve their own purposes.