Skip to: Site Menu | Main content

Star Light, Star Bright: How Astronomy Fails to Explain the Star of Bethlehem

The key problem is that the description of the movements of the Star is outside what is physically possible for any observable astronomical object.

See Also: The Star of Bethlehem: A Skeptical View (Onus: 2013)

By Dr. Aaron M. Adair
Department of Physics, the Ohio State University
February 2014

For many people around the world, the liturgical calendar brings about the cheer of the Christmas season, in which many of the tales of the birth of Jesus, some canonical (such as his birth in Bethlehem), others evolving from other traditions (such as the names of the Wise Men or Magi), are told in plays, in films, and on television. In a somewhat unexpected turn, the world of science, usually seen as orthogonal to faith, matches the liturgical calendar, and in this season, planetaria around the world will have presentations about one canonical story, the Star of Bethlehem.

The attempts to explain the Star astronomically in planetarium shows are a tradition that is older than many of the cherished Christmas carols and the miracle on 34th street, going all the way back to the 1930s when planetaria were starting up be built en masse. Along with news reports, TV specials, and new scientific articles and books, the effort to explain the 2000 year-old miracle over Bethlehem has become almost as iconic of the holidays as Coca-Cola cans featuring Santa Claus, or at least for one subset of the population. However, these astronomical and astrological searchers for the Christmas Star are done with little in the way of the light cast by biblical studies, or even knowledge of the original language of the Gospels. It seems that for Bible scholars, a naturalistic account of the Star of Bethlehem went out of fashion by the mid-19th century, and more and more these sorts of investigations have become the province of interested scientists.

So what theories have been proposed? It may be easier to say what hasn’t, considering how journalist Werner Keller put it back in the mid-20th century: “Anything that has ever moved across the canopy of heaven, as well as much that has only existed in men’s imaginations, has been dubbed the Star of Bethlehem.”1 This now includes things outside of normal science, such as a mystery planet invented by pseudo-Assyriologist, Zecharia Sitchin, and others2 or even an alien space craft.3 But if one were to focus on the scientific literature, there are probably three major contenders that are promoted: a comet, a nova or supernova, and some sort of planetary conjunction or other astrologically significant arrangement of the planets.

Comets are spectacular objects to see in the sky, producing tails of gas and dust as they near the sun, their surfaces boiling away and leaving a visible trail over millions of kilometers. However, these ‘hairy stars’ are almost universally considered a terrible omen, and the few exceptions seem to be politically motivated, such as the comet of Caesar Augustus in 44 BCE. It is hard to understand how the Magi would have been so willing to take a sign so often seen as evil and transform it into something not just good, but indicating a person worthy of worship.

A nova and its even more powerful cousin, the supernova, are literally stars blowing up, potentially brighter than a galaxy of stars. The idea of this being the Star of Bethlehem inspired an award-winning story by Arthur C. Clarke back in the 1950s, and since then it has been proposed by various astronomers in their literature. However, we have no good evidence that any such explosions were seen around the time of Jesus’s birth, and how they would have been interpreted by sky watchers of the past is uncertain at best; at worst, they would have been seen in the same way as comets, if Chinese annals that include comets and novae are any indication.4

But the greatest attention has gone into the movements of the planets and what sort of astrological symbolism they may have provided to the alleged eastern astrologers. Those proposals, though, are legion. Be it the conjunctions of Jupiter with Saturn in 7 BCE, Jupiter and Venus in 3 and 2 BCE, the occultation of Jupiter by the Moon (where the Moon is in front the planet as seen from the Earth, thus hiding it) in 6 BCE, and still more. Where to look in the sky for the coming of the Jewish king is also diversely argued, with various authors suggesting to look to the constellation of Pisces, or Aries, or Leo, or Andromeda, or Virgo, or Capricorn, or Aquarius, or others still. Of course we may forgive this level of confusion considering the fact that ancient and modern astrologers are no more consistent.5 This is also the great stumbling block to all searches for what would have been astrologically interesting to sky watchers of the past: how they would have been interpreted cannot be guessed at much better than chance.6

But considering the Magi, astronomers have also made several assumptions that fail under examination. We actually see in the works of these Zoroastrian priests that they did not have an astrological tradition, and this would not change until centuries later.7 Their interest in Judaism and Christianity is also undermined by inscriptions from the third century showing how the leaders of the magi actually persecuted Christians and Jews.8 It seems as if no one of their cast came and worshipped at the feet of a Jewish infant who went off to found an inspirational ministry. The importance of the infant does not seem to be in the minds of the magi, but instead in the eyes of modern astronomers. One must also wonder what would have been the Roman response to Persian political figures coming to one of their client kingdoms and establishing another as its ruler. So it seems that there are no signs that any astrological phenomenon did or would have interested the magi.

Should one instead turn to how most other theologians of the past and critical scholars of the present view the story, then astronomy has little to say in the matter. That was, for example, the position of Augustine, who said the supernatural ways of the Star divorced it from scientific investigation.9 The famous astrophysics, Johannes Kepler, who in his 1614 chronological treatise did use astrology to explain aspects of the story of the journey of the Magi, still believed the Star itself to be a divine object that hovered over a particular hovel, low in the air.10 Centuries later, Mark Allen Powell states “The leading of this star is so obvious that it requires no scholarly interpretation. It points out the exact house where Jesus has been born. As a sign, it appears to function as a divine portent so blatant that any fool could follow it.”11 The late Raymond Brown also agreed on the miraculous aspect of the Star, saying “I have not found an astronomical proposal that fits [the Gospel description of the Star] literally.”12

The key problem is that the description of the movements of the Star is outside what is physically possible for any observable astronomical object. The Star is said to guide the Magi south towards Bethlehem from Jerusalem, but all stars and planets in the sky will travel along from east to west over a period of a few hours, the time it takes to walk from Jerusalem to Bethlehem. Moreover, the Star is said to stop in place and hover over a particular lodging, acting as an ancient GPS unit. Besides nefarious ETs, this is something that is outside the purview of astrophysics and any future scientific investigation. I thoroughly go through the text to make this point in my book on the matter, The Star of Bethlehem: A Skeptical View (Onus: 2013).

So why is it that so many trained and amateur astronomers search so diligently for an explanation for the Star of Bethlehem? In part there is the problem of simply not being able to access the story in its original language or context. While Brown thought that scientists did not take everything literally in Matthew,13 in fact some have argued that the language of Matthew was scientific and using ancient astronomical vernacular. How the Star “went before” and “stood over” are believed by some to be retrograde motion and stationary points, though these are with respect to the stars in the night sky rather than the traveling Magi, as the context indicates. This attempted alignment between the astronomical verbiage and the Gospel account is particularly notable in the arguments of astronomer Michael Molnar, who thinks the words of Matthew describe the retrograde motion of the planet Jupiter and its apparent stopping in the sky, all due to the optical illusion caused by the movement of the planets around the Sun, with ancient technical terms.14 Unfortunately, his beliefs about the Greek words used in the Gospel of Matthew are unfounded and due to a lack of knowledge of basic rules of noun declension.15 But more generally, there is an inability to access the Gospel as scholars do, and this allows another variable to randomize the results.

However, a lack of knowledge does not explain the continued fascination with the subject. The motivation perhaps is not too hard to guess: this is a way of showing something from the stories of the Bible is verifiably, demonstrably true. Certainly it would be a comfort to a faithful scientist to reveal something about Christian history using modern tools and physics. The discovery of the Star in astronomy also makes the other stories of Jesus, including the fantastical, more believable. This would also be true of planetarium attendees, as the holidays shows (in my experience as a show presenter as well as anecdotes from others) are some of the most popular, bringing in the crowds year after year.

There is also an effort to use these hypotheses for evangelizing, though this isn’t so much the objective of the speculations of the scientists. The popular documentary on the Star by Texas lawyer Fredrick Lawson,16 for example, is very much a tool in showing how something from the story of Jesus can be proven to a modern audience. And in many ways that is the point of these investigations into what the Star was: having the power of science to show the truth of something in the Gospel message. One could compare this with archaeological expeditions trying to find proof of the Exodus, though astronomical reconstructions of past skies are less fraught with difficulties.

This is in stark contrast with how science and religion are seen usually as interacting. Be it the Galileo affair or the theory evolution, the idea of conflict between these ways of thinking is very common. But in this case, there is apparently peace and, in fact, dialog. Fitting to the holiday it relates to, there are tidings of comfort and joy. However, this peace is brokered by a lack of awareness of the last 150 years of biblical studies and basic reading of the original text. There is a literal reading of the story without being able to read it, and yet this same literalism doesn’t lead to modern scientific explanations for the virgin birth or the resurrection. The rationalization of the Gospel is very limited in scope and functions in a vacuum of the scholarly work on the subject. The narrow extent of rationalizations may be in part because it is relatively easy to use computers to investigate ancient skies, but we do not have Jesus DNA to see if there is some chromosomal oddity, and artifacts such as the Shroud of Turin are controversial at best. The ignorance of biblical studies, on the other hand, lacks a decent excuse, other than it makes the whole enterprise ill-founded. A peace founded on ignorance (or denial) is unlikely to be stable, but this is the apparent nature of the last century or two of seeking the Star of Bethlehem in the heavens.

What this also means is that there is a disconnect between what has been the scholarly consensus for a very long time and the popular imagination of the story. For example, the 2010 BBC production of The Nativity lacked a Star that directly guided the Magi to their destination and instead left it up in the skies as a planetary conjunction. Fox News’ Bill O’Reilly used the hypothesis of the Star as a comet in his recent bestselling book, Killing Jesus.17 The documentary by Larson, mentioned above, has also proven to be very popular and claimed by Larson to be one of the best-selling DVD documentaries. This should cause scholars to take note as institutions of education, such as planetaria, let alone mass media, are continuously used each year to distance the popular understanding of the Bible from what has been the view of those who have considered the matter professionally. And because science is used, it has an amplified ability to persuade an audience.

Those who do have the necessarily knowledge of biblical studies have made plenty of progress, in particular comparing the story to the prophecy from Numbers 24:17 about a rising star as a sign of a Jewish monarch. The story of Herod, the interpreters of signs, and the attempt on the life of baby Jesus, also seem to model the story of Moses, especially in extended versions seen in sources such as the writings of the 1st century Jewish historian, Josephus.18 The guiding nature of the Star also seems to function as a contrasting foil to the star that guided Aeneas to founding Rome.19 The details of language and structuring of the story have become far better understood using methods of literary analysis than by affirmations of historicity. On the other hand, not everything is certain. The relationship between the Star Hymn in one of the letters of Ignatius of Antioch (Eph. 19) and the Star in the Gospel of Matthew remains unclear. Did Ignatius, in the second century, know Matthew’s story, and if so why are they so different?20 Or could it be that Ignatius knew of some other tale about a star, perhaps one related to Jesus as the Morning Star (Rev 2:28, 22: 16; 2 Peter 1:19)? This will require future explorations, which I hope to do, but unfortunately astronomy is not likely to provide much in the way of illumination.

If there is a Yuletide message then for scientists in this, it is best to be cautious when venturing into explaining things where professionals have explored the matter and know very important information that isn’t in the repertoire of someone with a Ph.D. in astrophysics. Unfortunately, the methods used by astronomers and other scientists are not unlike what was seen in biblical studies in the early 1800s. If college students have to learn about physics after 1835 (and they will if I have anything to say about it), then so should scientists know about what changes in biblical studies came after Heinrich Paulus before exploring the matter. This may also come to relieve planetarium workers, who have come to collectively refer to the Christmas Star as the ‘SOB’. For Bible scholars, there needs to be better vocalization that the astronomers are not really providing answers, and a lack of exact knowledge about planetary science is not something that should limit one from criticizing these naturalistic hypotheses that are unaware of the literary qualities of the story. Let us all better explain the nature of the Gospels, but as story first, very carefully as history second (if at all), and not as science.


1 Werner Keller, The Bible as History (Barnes & Noble: 2005), p. 325.

2 Barbara Hand Clow, Chiron: Rainbow Bridge between the Inner and Outer Planets (Llewellyn: 1987), p. 21; Douglas A. Elwell, Planet X, the Sign of the Son of Man, and the End of the Age (Defender Publishing: 2011).

3 Barry Downing, The Bible and Flying Saucers (Avon: 1970), p. 134.

4 Cf. Ho Peng Yoke, “Ancient and Medieval Observations of Comets and Novae in Chinese Sources”, Vistas in Astronomy 5 (1962), pp. 127-255.

5 Aaron Adair, “The Star of Christ in the Light of Astronomy”, Zygon: Journal of Science & Religion 47 (March 2012), p. 21.

6 Cf. John McGrew and Richard McFall, “A Scientific Inquiry into the Validity of Astrology”, Journal of Scientific Exploration 4 (1990), pp. 75-83; Rob Nanninga, “The Astrotest: A Tough Match for Astrologers”, Correlation 15 (1996), pp. 14-20; John David North, Horoscopes and History (Warburg Institute: 1986), p. xi; cf. Ptolemy, Tetrabiblos 1.2.

7 Gerard Mussies, “Some Astrological Presuppositions of Matthew 2: Oriental, Classical and Rabbinical Parallels” in Peter Willem van der Horst, ed., Aspects of Religions Contact and Conflict in the Ancient World (Faculteit de Godgeleerdheid Universiteit Utrecht: 1995), pp. 25-44.

8 Mary Boyce, Textual Sources for the Study of Zoroastrianism (Brill: 1975-1991), pp. 112-113.

9 Reply to Faustus the Manichean 2.6f.

10 Christian Frisch, Kepleri Astronomi Opera Omnia (Heydern & Zimmer: 1858-1871), vol. 4, p. 346.

11 Mark Allen Powell, “The Magi as Wise Men: Re-examining a Basic Supposition.” New Testament Studies 46 (2000), p. 11.

12 Raymond Brown, The Birth of the Messiah (Random House: 1993), p. 612.

13 Brown, Birth, p. 612.

14 Michael Molnar, The Star of Bethlehem: The Legacy of the Magi (Rutgers: 1999), p. 90. The phenomenon of retrograde motion, in which the planet stops moving relative to the background stars in an easterly direction, and then moves westward for a period of days or weeks, and then reverses again, is due to the Earth passing by another planet. It is the same as how when passing a car on the highway it temporarily appears to move backward. For centuries it was explained using the system of cycles on top of cycles, or epicycles, about the earth until the Copernican revolution.

15 J. Neville Birdsall, Review Symposium “The Star of Bethlehem”, Journal of the History of Astronomy 33 (2002) , pp 391-394.

17 Bill O’Reilly, Martin Dugard, Killing Jesus (Henry Holt & Co.: 2013), p. 15. However, the authors do confuse points of astronomy, such as when they say the comet moved in the sky due to the Earth’s orbital motion rather than its rotation.

18 Josephus, Antiquities of the Jews 2.9 §§ 2-3.

19 Aaron Adair, The Star of Bethlehem: A Skeptical View(Onus: 2013), pp. 118-120.

20 On how Ignatius appears to be independent of Matthew, see William Schoedel, Ignatius of Antioch: A Commentary on the Letters of Ignatius of Antioch (Fortress Press: 1985), p. 9.

Comments (8)

It's certainly worth teasing out Matthew's meaning. I disagree with Powell's view that the Magi are not wise men. Herod cannot dismiss them as fools or crackpots and he enters serious discussion with them. It is presumed that they are far too smart for any simple trick, like having a spy follow them, to work. They contrast with Herod's astrologers/astronomers by being wiser, not by being more childlike.
The idea must be that they possess some remarkably clever technique of observation and calculation which enables them to identify the star as royal, though not to predict its course all the way to B'lem. Only they can do this and when their complicated procedures enable them, along with the hint that they have picked up in J'lem, to identify the star again, which they must in the terms of the story have feared that they could not do, they rejoice. Their entry into the realm of joy makes them less like scientists and more like visionaries, heirs to Balaam: like Balaam, they had begun by sensing what was not near. So the star's relationship to the house seems more like an ecstatic vision than the result of observation.
This may not be a theological story that science can elucidate but I think that it does offer a theological view of science as one of the ways of ascent to the presence of God. Which may be a little optimistic.
#1 - Martin - 02/08/2014 - 14:21

The Jupiter-Venus conjunction of June 17, 2 BCE seems a likely candidate. One astrological interpretation of the conjunction would have been the mating of the two deities. One can imagine an observer in Babylon noting the brilliant conjugal event in the evening sky just after sunset, roughly in the direction of Jerusalem, marking an X on his calendar for the arrival of the prophesied messiah nine months hence.

But it raises the question in Matthew 2:2 and 2:9 whether the star was in the east, or the observers.
#2 - Roger Cooper - 02/10/2014 - 19:51

It may be fair to say that the Magi were not as incompetent as Powell suggests, but I think Powell is correct in noting that our interpretation of them is us filling in the blanks of Matthew. Realizing this as a point of reader response criticism should be helpful. And Powell notes how the Magi were interpreted as the "wise men" when astrology was getting some better recognition in medieval Europe. In our times, we try to see them as scientists of sorts, so again them seem wise enough to interpret things. However, what I see Matthew trying to do is having Gentiles realize what is happening, while the corrupt Jewish elite is none the wiser. This also fits into the Great Commission at the end of the Gospel.

The Jupiter/Venus conjunctions in 2 BCE have the first problem of not fitting Matthew's timeline, since Herod died in 5/4 BCE. So the thesis requires changing history to make it work. But even so, there isn't any evidence that such a conjunction would have had the positive interpretation. In my book, I actually show that the cuneiform astrological records actually say this was a terrible omen. Also, Jupiter/Venus conjunctions happen all the time, though not necessarily as close as was observable in 2 BCE. Still, something that happens several times in a lifetime is hardly the best way to announce the one and only Son of God. As for the Star being "in the East", it seems best understood as it is referring to the star rising above the horizon; stars rise in the east, hence the confusion. But I also have my own peculiarities in interpreting the phrase en te anatole, which I discuss in my book a bit but will go into better detail in future work.
#3 - Aaron Adair - 02/11/2014 - 00:19

Thanks for the information about the negative connotations of conjunctions. Mind you, I don't really understand why the hypothesis of conjunctions has been taken so seriously in this context. Our source refers to a star, and a conjunction isn't a star but a pair of stars, which is obviously different. And the movements ascribed to the star don't in any sense fit in with a conjunction.
The magi are heirs to Balaam, who was a visionary rather than an astrologer. But I can't think it's right to regard them as in any sense childlike. They have a status as representatives of the eastern nations whom Matthew hoped to convert and they carry gifts worthy of a king. They're serious people.
#4 - Martin - 02/11/2014 - 18:24

I would agree the 2 BCE conjunction raises a problem with Matthew's timeline, but of course this timeline and Matthew's narrative in general are problematic for other reasons. One is the lack of any evidence for the slaughter of the innocents, which drives the argument that Jesus was born before the death of Herod.

I would also agree that conjunctions happen all the time, but this one was hardly commonplace. It was so close that it would have made the two brightest planets in the sky a scintillating and memorable event. As Newman (1) summarizes, a conjunction with 3 minutes of separation as estimated by Sinnott would be expected at a frequency of once every 1154 years. And if one takes Martin's estimate of 0.5 minute, or Carroll's of 0.1 minute, the event would be even rarer at once in 6923 or 34,615 years respectively.

We should remember that Matthew was writing at a distance of some 80 years or more and he almost certainly did not have accurate dates for Jesus' birth, Herod's death, or for the celestial events that occurred about that time. These ambiguities only served his purpose in constructing a plausible timeline. In the power vacuum and period of instability that followed Herod's death, the spectacular conjunction of June 17, 2 BCE would have fired popular expectation for the imminent arrival of the Messiah, and created an indelible memory which lent itself to Matthew's theme of Jesus being the fulfillment of that prophesy.

(1) Newman, Robert C., 2001, The Star of Bethlehem: A Natural-Supernatural Hybrid?, IBRI Paper. (
#5 - Roger Cooper - 02/11/2014 - 21:50

It can hardly have created an indelible memory if there is no record - and there isn't - of either a religious or a political movement or astrological or scientific speculation based on it. Matthew surely means that the event was not even noticed until the Magi made startling claims about it. I just can't see the attraction of the Conjunction Hypothesis, since no one mentions or hints at conjoined stars or their astrological significance.
#6 - Martin - 02/15/2014 - 12:07

I support M. Eugene Boring's commentary on Matthew in "The New Interpreter's Bible". He considers the navitity story as a midrash and the literary structure of Matthew as chiastic.
From a notebook of articles I have this statement that I think I wrote: "The birth story is a midrash focusing on Jesus as the fulfillment of Scripture--using a poor copy of the Septuagint--and in the chiastic style is fulfilled in reality with persecution by govenment authority, fleeing to Egypt/mitzrayim(death),returning(resurrection),proclaiming his message through his apostles to the gentiles (the ones who understand the signs).
#7 - - 02/15/2014 - 14:56


Just about any particular planetary alignment or conjunction can be construed to say it is extremely rare. It is very rare for Jupiter and Saturn to be in conjunction exactly on the vernal equinox. The question, however, is what is the evidence that such a conjunction would have been given special considerations? Concerning Jupiter-Venus conjunctions, I provide cuneiform sources that show such a conjunction was considered a sign of the death of kings, though any particular conjunction could be interpreted any way an astrologer wanted. That's because astrological methods are exceedingly loose; you can get whatever you want. So taking a given conjunction, which happens periodically (Jupiter-Venus ones happen about every two years), and specifying how this particular one is different from the others indicates nothing to a modern researcher that it would have had a particular meaning to an ancient audience. More importantly, astrological horoscopes cared not for how close the stars were apparently in the night sky; there is no evidence that particularly close conjunctions (with respect to both right ascension and declination) had greater astrological import.

So, we have no evidence that the conjunction in 2 BCE fired popular or elite imaginations. It's not something mentioned in any record, and Matthew's account has no connection to it, since the Star there is obviously supernatural and in the atmosphere, not some conjunction in the sky. Without some external record showing it was important to people, such as the records we have for Caesar's comet in 44 BCE, there is no grounds to say how the conjunction would have been interpreted, or even if it would have been special at all.
#8 - Aaron Adair - 02/16/2014 - 18:55

Use the form below to submit a new comment. Comments are moderated
and logged, and may be edited. You must provide your full name.
Inappropriate material will not be posted.

E-mail (Will not appear online)