A few years ago, while I was living in Southern California, a local church asked me to present a talk on the Christmas Star as part of their Christmas outreach events. Needing to dive into current and historical interpretations of this most famous astronomical phenomenon, I did some research at the Biola University library, where I found several books on the subject. 

One in particular was recently published, caught my attention, and stood out as the most compelling. Colin Nicholl’s The Great Christ Comet: Revealing the True Star of Bethlehem commended itself with sound biblical and historical scholarship combined with in-depth astronomical insights. Professor Nicholl, with a PhD from the University of Cambridge, is a theologian holding a high view of Scripture. But what also impressed me was his commitment to engage with astronomers in his evaluation and presentation of explanations for the Star.

If the lights of the physical heavens were created “for signs and for seasons,” and if an astronomical phenomenon appeared at the precise time and place to convince pagan astrologers of the birth of the Jewish Messiah, then surely this counts as one of the most outstanding examples of intelligent design. Exactly what the Star was has invited speculation for centuries.

As bright as the Star evidently was, for almost two millennia its identity has been enshrouded in a mysterious darkness. (p. 25)

A Compartmentalized Approach 

Nicholl suggests that part of the difficulty with arriving at a satisfactory theory for the Star stems from a compartmentalized approach, with astronomers or theologians undertaking the task within their separate disciplines. Astronomers are largely “untrained in Biblical studies” while Biblical scholars find themselves “in alien territory” when considering the astronomical possibilities. (p. 69, p. 26)

A possible interpretation of the account of the Magi (or Wise Men) and their luminous guide that needs to be addressed right away is that the star had no basis in astronomy at all, that it was at worst a mythical narrative, or at best a one-off supernatural phenomenon. Nicholl rejects these hypotheses for two reasons. One is the nature of the Gospel accounts:

However, the skepticism is unwarranted. We have already seen that the Gospels are ancient Greco-Roman biographies that seek to tell the story of Jesus in a historically faithful way, based on sources deemed reliable, and that the story of the Magi was regarded by Matthew as true and has strong historical credentials. (p. 87)

The second reason Nicholl offers for dismissing the mythical/supernatural interpretation is that 

the claim rests on astronomical ignorance. As this study will demonstrate, every element in Matthew’s description of the behavior of the Star is consistent with established astronomical facts. (p. 87)

Nicholl notes that the description of the Star in Matthew 2:1-18 “almost certainly reflects the observational perspective of the Magi.” As such, the primary interpretive direction should lie along the path of finding a valid astronomical explanation. The bulk of Nicholl’s research follows this path and focuses on bringing together Scriptural clues with astronomical possibilities.

A Triple Conjunction?

Most readers have probably already heard, as I had, one or more hypotheses for an astronomical explanation of the Christmas Star.

The hypothesis that the Star of Bethlehem was the triple conjunction of Jupiter and Saturn in 7 BC is perhaps the single most popular view. (p. 69)

A conjunction of planets occurs when the planets appear close to one another as viewed from Earth. This normally occurs for Jupiter and Saturn every 19.76 years, but a “triple conjunction” occurs more rarely (about every 139 years) when these planets appear to approach each other three times within the period of about one Earth orbit. In the 7 BC triple conjunction of Jupiter and Saturn, these two gas giants approached three times within one degree of each other, against the backdrop of the constellation Pisces. (p. 70)

On December 21, 2020, Earth’s view of Jupiter and Saturn coalesced in the night sky to just one-tenth of one degree — so close that they could easily appear as a single “star.” This was certainly not the case for a conjunction such as the ones in 7 BC, when the planets’ angular separation was one degree, or about twice the diameter of the full moon. I remember watching the nightly progression of Jupiter closing in on Saturn in late fall of 2020. When they were still about one degree apart, there was nothing particularly spectacular about it. Nonetheless, one could conceivably overlay an interpretation the event, based on the ancient character associations of Jupiter and Saturn. According to one such understanding, the sign would mean, “The King is overtaking Death.”

After carefully evaluating several other proposals for possible astronomical events giving rise to the Star of Bethlehem, Nicholl finds them all wanting on major points. One of these proposals is that the Star was a comet, typically Halley’s Comet, or another comet seen in 5 BC and mentioned in Chinese astronomical records. (p. 127) A careful analysis of the timing of the appearances of these comets, and their locations and durations of visibility in the sky, shows that identifying the Star with either of these phenomena is untenable.

Revealing the Main Conclusion

And now, the main conclusion of Nicholl’s research:

In spite of the weaknesses of the Halley’s Comet and the 5 BC Comet hypotheses, the evidence that the celestial phenomena that the Magi witnessed were caused by a comet is overwhelming….When we also consider that the Star was visible for at least 1-2 years, the possible identifications are narrowed down to two — a supernova or a large, productive, long-period comet… (pp. 132-133)

But supernovae leave a detectable remnant, visible for thousands of years after the initial explosion, and “no remnants of a supernova 2,000 years ago have ever been discovered.” (p. 78)

A focus of Nicholl’s evaluation of various astronomical hypotheses has to do with how well they complement the famous question of the Magi when they arrived in Jerusalem: 

Where is he who has been born king of the Jews? For we saw his star when it rose and have come to worship him.

Matthew 2:2, ESV

One of the basic astronomical facts that I’ve taught to hundreds of introductory astronomy students is that, due to the Earth’s counterclockwise rotation (as viewed from above the Earth’s north pole), all celestial objects appear to rise in the east and set in the west. Just seeing a star rise (in the east) would be unremarkable. Nicholl proposes that the Magi referred instead to a particular moment of rising, called the “heliacal rising” of the star — at the time of year when it can first be seen low on the eastern horizon in the early dawn, just before the light of sunrise causes it to fade from view.

A Long-Period Comet 

Upcoming heliacal risings of stars and planets would have been predictable to the Magi. The heliacal rising of a long-period comet, on the other hand, would have appeared exceptional.

Indeed no other entity’s heliacal rising can compare in majesty to that of a great comet speeding away from the Sun immediately after its closest encounter with it….This renders a great comet by far the most natural celestial candidate for the role of the Star that rose in the east. (p. 134)

Comets also uniquely move across a significant portion of the sky within a period of weeks, especially around the time of the perihelion.

A comet with orbital elements within certain ranges could have heliacally risen in the eastern sky and, shortly thereafter, shifted to the western evening sky, and then migrated to the southern evening sky on schedule to usher the Magi to Bethlehem and point out the location of those where baby Jesus was….The setting of a tailed comet on the western horizon is uniquely qualified to be perceived to “stand over” a particular house. (pp. 134, 136)

Nicholl builds his case for the Bethlehem Star being the appearance of a long-period comet entering the inner solar system on a retrograde orbit, narrowly inclined to the ecliptic (the plane of the Earth’s orbit around the Sun). A long-period comet would typically have a greater reserve of volatile material and could thus develop a much greater brightness as it warms on its approach to the Sun.

He further elaborates the significance that would be attached to such an unexpected cometary visitor by connecting its appearance to certain prophetic biblical passages, such as found in Balaam’s prophecy in the Old Testament:

I see him, but not now; I behold him, but not near: a star shall come out of Jacob, and a scepter shall rise out of Israel.

Numbers 24:17, ESV

Ancient and modern scholars commonly accept that Balaam was speaking of “long-tailed comet scepter.”

Appreciating the Dramatic Impact 

To elucidate the dramatic impact that the heliacal rising of a great comet must have had on the Magi to launch them on a 550-mile, five-week journey to Jerusalem, bearing gifts for a newborn King, Nicholl draws inspiration from the heavenly drama described by John in Revelation 12:1-5. In this passage, “the narrative of Jesus’s birth is told in what are clearly celestial terms.” Nicholl suggest that John is “consciously recalling the heavenly wonder that attended Jesus’s nativity.” (p. 154)

A full description of this heavenly narrative would take us beyond the scope of this article, so I’ll leave it as a teaser and a motivation to read the full account in Nicholl’s book. Endorsements for The Great Christ Comet attest to his masterful treatment. Distinguished professor of philosophy J. P. Moreland calls it “a stunning book.” And Oxford University mathematician John Lennox welcomes it as “an outstanding book, quite breathtaking in the range of its scholarship.”

My own reading of this delightful book leaves me in awe at the design of the cosmos that includes the exquisite orchestration of the fine-tuning of planetary orbits and the slight gravitational nudges on a frozen mass of cometary material from the Oort cloud. That orchestration, it seems to me, sent a comet on a precise orbital track, hurtling through the inner solar system, in order to dramatically portray in real time long-foretold events.