What was the Star of Bethlehem?

The Star of Bethlehem is a celebrated sight in the history of Christianity, but what was it exactly? Was it a star, a meteor, a comet? A new theory proposed it was multiple events!

“I see him, but not now; I behold him, but not near–a star shall come forth out of Jacob and a sceptre shall rise of out Israel; it shall crush the borderlands of Moab and the territory of all the Shethites.” -Balaam, Numbers 24:17

Imagine yourself a young tax collector in the Roman Empire. You have taken it upon yourself to write down the tumultuous times you’ve lived through and anything you can remember about the leader that you’ve followed. Your name is Matthew and you are writing about Jesus of Nazareth, grappling with how to start the story.

Matthew decided to start with the beginning of the whole of Christianity: the virgin birth of Jesus. He starts with a single astronomical event, one that does not show up in any of the other Gospels. According to Matthew 2:2,

$^1$In the time of King Herod, after Jesus was born in Bethlehem of Judea, Magi from the East came to Jerusalem, $^2$asking, “Where is the child who has been King of the Jews? For we have seen his star at its rising and have come to pay him homage.

And Matthew 2:7-11,

$^7$Then Herod secretly called the Magi and learned from them the exact time when the star had appeared. $^8$Then he sent them to Bethlehem, saying, “Go and search diligently for the child and; when you have found him, bring me word so that I may also go and pay him homage.” $^9$When they had heard the king, they set out; and there, ahead of them, went the star that they had seen at its rising, until it stopped over the place where the child was. $^{10}$When they saw that the star had stopped, they were overwhelmed with joy. $^{11}$On entering the house, they saw the child with Mary his mother; and they knelt down and paid him homage. Then, opening their treasure chests they offered him gifts of gold, frankincense and myrrh.

What is striking about this account is how important the Star is to Matthew. This Star is not mentioned at all in any of the other three Gospels. Why isn’t it mentioned if it was clearly such an important part of the Nativity? The short answer is that four different people wrote the Gospels with four different purposes in mind. Luke, John, and James didn’t write about the Star because they didn’t find it as important as Matthew did.

But what could this Star have been? There are only three options to explain this mystery:

  1. The Star is a myth or a legend. Matthew added it to the New Testament to fulfill the prophecy of Balaam that a star would announce the birth of the Messiah. In that case, the Star did not exist.
  2. The Star is a genuine report of an astronomical event that took place, albeit the story has been modified over time and incorporated into Matthew’s Gospel.
  3. The Star was a miracle, which is beyond science to explain.

Plenty of stars have been used in the past to mark the birth or death of a king or ruler. The deification of an emperor could have been marked by some event seen immediately after his death: a comet, a strange cloud, an active volcano. Matthew may have added the Star to deify Jesus in order to convert the Roman pagans to the Christian cause. Option #1 might be a satisfactory option!

We must also remember that the events described in the Bible are an account of the works of God. God does not have to justify His acts and can make a new star shine if He so desires. Option #3 is a perfectly reasonable option for the faithful.

However, it can also be argued that the Bible is an account of historical events, albeit from an evangelical point of view. Key events such as the census decreed by Julius Caesar are known to have happened. The only problem is that the records are not eyewitness accounts and we do not have any photographs or current astronomical data to analyze. However, since I am neither a literay or religious expert, we will take what we can get and deduce what the Star of Bethlehem could be!

The Birth of Christ

First, we have the problem of when was the Nativity? Was Jesus truly born on Christmas Day or was he born on some other day?

Our modern calendar was created during Roman times. Originally it counted years from the founding of Rome and had ten months and a system of complicated leap-months. Julius Caesar added two more months (July and August) and changed the leap-months into leap-years. After a small revision by Pope Gregory XIII in 1582, the modern calendar has been unchanged.

Both the year and the date of Christmas was fixed by a Scythian monk and church scholar, Dionysius Exiguus, in 525 CE. To do this, he used the most accurate measurement of time available to him: the reigns of the Roman emperors. By summing up the lengths of their reigns and working backwards, he fixed the birthday of Jesus to a stunning degree of accuracy for the time.

Unfortunately, he committed two errors. First, he omitted the year zero. Secondly, when adding up the Roman emperors’ reigns, he was off by five years. Paradoxically, that puts the birth of Jesus at about 5 BCE, five years before the birth of Christ! Most modern scholars give a larger range of 6-4 BCE, since we cannot know if Exiguss made more mistakes we haven’t caught yet. Using many hints from the Bible and from other historical sources, we can narrow down the birth of Christ to around March or April of 5 BCE. I won’t go into the details of that calculation, but those are the months agreed upon the most among scholars.

Now that we have the date of Christ’s birth, we can begin to investigate any astronomical events that could’ve happened in the skies that would cause the Magi to travel from Babylon or Persian to Jerusalem.

Simple Explanations: A Planet or a Comet?


Could it have been any of the planets? Venus is the brightest planet visible to us on Earth; perhaps it was Venus that the Magi saw. This is an old hypothesis and it had already fallen out of favor in the 19th century. Venus is in the sky almost continuously, and the Magi, as astrologers, would have known the motions of Venus and the other planets well. What’s not impossible is that the Star could’ve been Venis in combination with other planets. We’ll return to this later.

Was it a comet? If you were to visit the small Italian town of Padua and enter the Scrovegni Chapel you would see the Nativity scene painted on the walls of the building and above the manger sits a comet. Clearly the Italians have an answer! In fact, close examination of the history of the fresco and its artist, Giotto di Bondone, would tell you that the comet is none other than Halley’s Comet!

Adoration of the Magi
Adoration of the Magi by Giotto di Bondone

Halley’s Comet is a periodic comet, that is, a comet that returns to Earth’s skies in a short amount of time, i.e., less than 200 years. Halley’s Comet was famously found to return every 75-76 years by Edmund Halley, an eighteenth century mathematician and contemporary of Isaac Newton. After Venus, Halley’s Comet is a popular answer to our question.

However, working backwards and checking with ancient Chinese records, shows that Halley’s Comet likely found its way to Earth between August 26 and Ocotber 20, 12 BCE. This is outside even the generous estimates to the date of the Nativity. It is unlikely that Halley’s Comet was the Star of Bethlehem.

What About Multiple Planets?

Mercury and Venus above the Moon

Other popular theories involve what is known as a conjunction of planets. A conjunction is when two or more planets line up in the sky in such a way that they appear close together, yet, in reality, they remain millions of miles apart. Occasionally, the planets appear so close together as to overlap in what is known as an occultation. Conjunctions have always been important to astrology, and it is with little doubt that the Magi would have analyzed and ascribed great important to conjunctions.

Since the Magi would have known about conjunctions and occultations in their work as astrologers, it is extremely unlikely that any one particular conjunction would have pushed them to search for a newborn king in Judea. The Star of Bethlehem was propbably not a single conjunction or occultation.

Goodness Gracious, Great Balls of Fire!

Over the years, more and more people have suggested even more radical theories. Perhaps the Star of Bethlehem was a meteor! Most people have seen meteors in their lifetimes. They appear as bright streaks of light across the night sky as space rock left behind from comets fall to Earth, burning up in the atmosphere in the process.

Very occasionally, a larger meteor will fall to Earth, taking longer to burn up. This leaves a bright streak across the sky, often brigher than the full moon. This phenomenon is termed a “fireball,” lasting for 5-10 seconds. But there lies a problem: the meteor, even a bright fireball, would only last for a few seconds, not for the weeks or months it would take for the Magi to leave Babylon/Persia and travel to Jerusalem and on to Bethlehem.

It would require two fireballs, one to guide them to Jerusalem and another to guide them to Bethlehem, to fulfill the requirements of the Star of Bethlehem. Most people are lucky enough to see one fireball in their lifetime; to see two in the span of a few weeks would be extraordinary and extremely unlikely.

What About an Actual Star?

Up until this point, we’ve talked about planets, conjunctions, comets, and meteors, but was the Star just that—a star? A supernova or even a dimmer but still bright nova would be bright enough to guide the Magi on their journey! They would’ve seen the supernova as a “guest star”; only recently have astronomers discovered supernovae are the swan songs of massive stars, exploding and scattering their heavy-metal-enriched guts across the cosmos.

When we look in ancient records for such guest stars, the closest supernova to the date of the Nativity would’ve been the supernova of 185 CE, but of course that came nearly two centuries too late. No supernova was recorded between the dates of 12 BCE and 10 CE by any ancient civilization. Alas, a supernova is not the answer either.

What About Multiple Events?

But what if it wasn’t just one event? Wherever the Magi came from, they were clearly versed in astrology and religion. They would’ve been moved by the night sky and found deep meaning in the motion of the heavens. No single event was meaningful enough to them to think a king had been born in Judea. What if they saw a series of events, a series so compelling that the Magi fiercely persisted to observed the heavens for a further hopeful sign, then another, and then, finally, the crowning achievement: they saw the long-awaited STar that had been prophesied. If this was true, what might have been the first event?

One of the events might have been the triple conjunction of Jupiter and Saturn in 7 BCE. A triple conjunction is a rare event involving an intricate set of moveents between two planets. Instead of one planet making a single pass close to another in the sky, the two bodies pass, separate, pass a second time, separate again, and then pass a third time before separating for good. This can only involve the planets beyond Earth’s orbit: Mars, Jupiter, and Saturn.

The triple conjunction of Jupiter and Saturn in 7 BCE would have taken about seven months to complete the entire dance. During this time, other planets may join the pair in what is known as a “planetary massing.” Several planets may appear close together on the sky during a planetary massing. This would have been especially interesting to the Magi!

For a triple conjunction to qualify for the Star of Bethlehem, it has to be neither too common nor too repetitive; too many in a short time would be a severe blow to the theory’s credibility. In the years between 1000 BCE and 1 CE, there are 64 Jupiter-Saturn conjunctions, but only seven sets of triple conjunctions. Out of these seven triple conjunctions, all of them were bright, four of them could have been more readily associated with the Jews astrologically, and one was both! From this perspective, the only reason one would pick the 7 BCE triple conjunction for the Star of Bethlehem was hindsight: unknown to the Magi, this conjunction occurred close to the date of the Nativity.

YearsMinimum SeparationConstellation
980-979 BCE38 arcminPisces
861-860 BCE55 arcminPisces
821-820 BCE22 arcminLeo
563-562 BCE68 arcminTaurus
523-522 BCE65 arcminVirgo
146-145 BCE10 arcminCancer
7 BCE58 arcminPisces

If we are to explain the Star of Bethlehem as an “ordinary” astronomical event, what we need is an event, or a combination of events, so unusual, so remarkable that its significance would be obvious, at least to the Magi. As we have seen, no single event stands out. The fact that there are so many possible candidates shows that, almost certainly, none is sufficiently important to be the right one on its own. We can thus reject the suggestion that only a single object was involved. The only possible solution to the mystery, if we accept the notion that the Star did exist, is a combination of events. What series of events would have been of great importance and significance to the Magi but not necessarily to anyone else?

To answer this, let’s look at three interesting, but in now way extraordinary, events that happened between 7 BCE and 4 BCE:

  1. The triple conjunction of Jupiter and Saturn in Pisces between May and December 7 BCE.
  2. The planetary massing of Mars, Jupiter, and Saturn in Pisces in early 6 BCE.
  3. The object or objects observed by the Chinese and Koreans in Aquila/Capricornus in the spring of 5 BCE and/or 4 BCE.

The First Sign: A Triple Conjunction in Pisces

Early in May they would’ve seen Jupiter and Saturn start to approach each other in the sky. On May 29, they passed each other, slightly less than one degree to the north of the other in the constellation of Pisces. Knowing this constellation is associated with the Jews, they would’ve followed this with great interest. Through the late spring and early summer they would’ve seen how Jupiter and Saturn separated in the sky and might’ve felt disappointed that a real sign had not yet been given.

That would all change in August as they would’ve noted with excitement as Jupiter and Saturn approached each other once more. On September 29, the two planets again passed each other moving in opposite directions, again in the constellation of Pisces. As October passed, the Magi would have noted how the two planets separated, only to watch them turn around and start marching back towards each other throughout November. By December 4, a third conjunction occurred.

The Magi would have stopped to think about this. Three times in six months the royal planet and Saturn had met and then separated in the constellation of the Jews. Surely this meant that something important was about to happen in Judea. The fact that a royal planet was involved suggested that a royal event was imminent: a king would be born? One would die? King Herod was now an old man, hanging on to life—perhaps the sign referred to him? Saturn was regarded as an evil planet, and maybe this increased the Magi’s suspicions that the detested puppet leader of Judea was somehow involved. The Magi would have pondered long and hard about the possibilities, but, remembering previous disappointments, would have waited to see what else might happen.

The Second Sign: A Massing of Planets in Pisces

Once again, they would not have long to wait. As Jupiter and Saturn dipped down in the evening sky, Mars started to enter the constellation of Pisces. In February of 6 BCE, the three planets, Mars, Jupiter, and Saturn, were separated by only eight degrees in the sky.

The Third Sign: Two Pairings in Pisces

Pairings in Pisces

On the evening of February 20, 5 BCE, something else happened. The two-day-old Moon would have passed very close to Jupiter in the night sky. The Magi would’ve seen the pairing of the Moon and Jupiter and the more southerly pairing of Mars and Saturn. The Magi have now seen four events in Pisces in quick succession. All they needed was a clear sign, something that would be easy to see, unmistakably written in the stars.

The Final Sign: A Nova

In February or early March of 5 BCE, about a year after the massing of the planets and less than a year after the lunar occultation, a nova blazed over the border of the constellations of Aquila and Capricornus.

On first sighting the nova, the Magi would have known their wait was at an end. The conjunctions had told them to await news from Judea and, possibly, to expect the imminent birth of the Messiah. The occultations told them that the new king was indeed the Jewish Messiah. The nova now told them that the royal birth had finally happened. The final piece of the puzzle was in place, and the Magi would only have had to act.

The logical destination would’ve been the capital of the Jewish world: Jerusalem. In a maximum of six weeks, maybe five, from the moment of the apparition of the nova, the Magi would arrive in Jerusalem to seek their audience with King Herrod. By the time they would set out from Jerusalem, due to the natural motions of the sky, the nova would now appear in the south at dawn.

If we include the other observed factors, such as the planetary massing (not all triple conjunctions give rise to one) and the fact that the nova occurred fairly close in the sky to whear the triple conjunction had already been seen, we find a series of events so unique that they can happen together only once in every several thousand years.

$^9$When they had heard the king, they set out; and there, ahead of them, went the star that they had seen at its rising, until it stopped over the place where the child was. $^{10}$When they saw that the star had stopped, they were overwhelmed with joy. $^{11}$On entering the house, they saw the child with Mary his mother; and they knelt down and paid him homage. Then, opening their treasure chests they offered him gifts of gold, frankincense and myrrh.

For those who wish to find a purely scientific explanation for the Star of Bethlehem, something that makes it truly unique, this explanation is compelling. In this case, the skeptics who believe that Matthew added the Star for purely literary reasons are wrong and there actually was a Star of Bethlehem.

On the other hand, for those who look to the Star of Bethlehem for deeper meaning, who can say to them that such a rare combination of events was not indeed miraculous?

If you are interested in the discussion surrounding the Star of Bethlehem and what it could be, astronomically speaking, a great place to start is “The Star of Bethlehem” by Mark Kidger. It’s available on JSTOR for those who have access to it here.

Ray Garner
Ray Garner
TAMU Astronomy Postdoctoral Researcher

I’m a scientist, Star Wars fan, and amateur photographer raised in Georgia. My research interests include galaxy evolution, star formation, satellite galaxies, and nebular diagnostics.