Is There an Astronomical Explanation for the Star of Bethlehem?

hypergiant star
Some Christians hold that there was a star that appeared to herald their savior's birth. They often depict it similar to this shot of VY Canis Majoris, from Rutherford Observatory. No scientific evidence exists for the Christmas star, just a gospel story. Arthunter, via Wikipedia Commons. CC BY-SA 3.0

People around the world celebrate the Christmas holiday. One of the central stories in the Christmas legends is about the so-called "Star of Bethlehem", a celestial event in the sky that guided three wise men to Bethlehem, where Christian stories say their savior Jesus Christ was born. This tale is not found anywhere else in the Bible. At one time, theologians looked to astronomers for scientific validation of the "star", which may well be a symbolic idea rather than a scientifically proved object.

Theories of the Christmas Star (Star of Bethlehem)

There are several celestial possibilities that scientists looked into as the root of the "star" legend:  a planetary conjunction, a comet, and a supernova. Historical evidence for any of these is scarce, so astronomers had little to go on.

Conjunction Fever

A planetary conjunction is simply an alignment of heavenly bodies as seen from Earth. There are no magical properties involved. Conjunctions happen as planets move in their orbits around the Sun, and by coincidence, they might appear close to each other in the sky. The Magi (Wise Men) who supposedly were guided by this occurrence were astrologers. Their main concerns about celestial objects were purely symbolic. That is, they were more concerned about what something "meant" rather than what it actually was doing in the sky. Whatever event transpired would have needed to have special significance; something that was extraordinary.


In reality, the conjunction they might have seen involved two objects millions of kilometers apart. In this case, a "lineup" of Jupiter and Saturn occurred in 7 B.C.E., a year commonly suggested as the possible birth year of the Christian savior. The planets were actually about a degree apart, and that was likely not important enough to get the Magi's attention.

The same is true of a possible conjunction of Uranus and Saturn. Those two planets are also very far apart, and even if they appeared close together in the sky, Uranus would have been much too dim for easy detection. In fact, it is nearly imperceptible with the naked eye.  

One other possible astrological conjunction took place in the year 4 B.C.E when bright planets appeared to "dance" back and forth near the bright star Regulus in the early spring night sky. Regulus was considered the sign of a king in the astrological belief system of the Magi. Having bright planets move back and forth nearby could have been important to the wise men's astrological calculations, but would have had little scientific significance. The conclusion that most scholars have come to is that a planetary conjunction or alignment probably would not have caught the eye of the Magi.

What About a Comet?

Several scientists suggested that a bright comet might have been significant to the Magi. In particular, some have suggested that Halley's Comet could have been the "star", but its apparition at that time would have been in 12 B.C. which is too early. It's possible that another comet passing by Earth could have been the astronomical event that the Magi called a "star".

Comets do have a tendency to "hang" in the sky for extended periods of time as they pass near Earth over days or weeks. However, the common perception of comets at that time was not a good one. They were usually considered evil omens or premonitions of death and destruction. The Magi would not have associated it with the birth of a king.

Star Death

Another idea is that a star might have exploded as a  supernova. Such a cosmic event would show up in the sky for days or weeks before fading out. Such an apparition would be pretty bright and spectacular, and there is one citation of a supernova in the Chinese literature in 5 B.C.E. However, some scientists suggest it might have been a comet. Astronomers have searched for possible supernova remnants that might date back to that time but without a lot of success.


Evidence for any celestial event is pretty scarce for the time period where the Christian savior could have been born. Hindering any understanding is the allegorical style of writing that describes it. That has led several writers to assume that the event was really an astrological/religious one and not something that science could ever show happened. Without evidence for something concrete, that's probably the best interpretation of the so-called "Star of Bethlehem" — as a religious tenet and not a scientific one. 

In the end, it's far more likely that the gospel tellers were writing allegorically and not as scientists. Human cultures and religions are rife with tales of heroes, saviors, and other deities. The role of science is to explore the universe and explain what's "out there", and it really cannot delve into matters of faith to "prove" them.