¿Which is the Star of Bethlehem?

¿Which is the Star of Bethlehem?
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According to Christian tradition, 2024 years ago, three figures known as the “Three Wise Men” followed a star in the sky for days, which guided them through deserts, roads, and villages to Bethlehem. Beyond Christian belief, it is a curious story from an astronomical perspective. In fact, did you know that many religious stories we know have their origins in real astronomical events? The best example of this is in Roman mythology, where each revered god was named after a planet in the Solar System: Neptune, the god of the sea; Venus, the goddess of love; or Mars, the god of War.

These events led astronomers since ancient times to consider the possibility that the famous Star of Bethlehem really existed. The most interesting question arises: if it was indeed real, what celestial body in the sky does it correspond to? Fortunately, we won’t leave you in doubt, or at least, we will tell you the most valued theories so far, as astronomers have not yet pinpointed the exact star or specific event referred to in the story. However, they have their hypotheses on the table, and some seem quite consistent with the facts.

You might be wondering how it’s possible to know or study the exact position of the sky from as far back as 2024 years ago. Well, it’s quite simple: all celestial bodies follow Newton’s Laws! Yes, the scientist with the apple. These laws are not recent; they have always been the foundation for explaining how objects move in the Universe: planets, stars, comets, meteorites, even space debris!

With common rules for all times, astronomers can easily “rewind” and know the position of each star and celestial body in the first days of January over two thousand years ago. From there, they only need to propose probable hypotheses and check if they match reality. Here are some of the theories considered so far!


Did you know that the first option was proposed by Johannes Kepler in the 16th century? And it wasn’t just a star or a planet in the sky, but the combination of two planets and a satellite. In other words, a conjunction. It’s a type of phenomenon that occurs when there is an alignment in the sky of several planets, which is seen from Earth and provides a lot of brightness. The brightness will be even greater the closer the bodies come to forming a straight line.

Kepler discovered that, around the years of Christ’s birth, there had been one of these alignments between Jupiter, Saturn, and the Moon. He directly linked it to the Star of Bethlehem, assuming it was a very bright conjunction that appeared in the sky in those December days. However, this idea was discarded when studied with more modern and advanced techniques, as everything indicated that the planets did not come as close as the story suggests. In fact, an almanac found in a Babylonian observatory supports this version: the date is not even marked as a conjunction, indicating that contemporaries did not attach much importance to the event.


Probably the most well-known comet with Earth in its orbit is Halley’s comet. And for good reason! It is the brightest, visible to the naked eye, and, in most cases, its 76-year orbit allows a large percentage of people to enjoy it once in their lifetime. So, if it is still such a striking object today, the inhabitants 2024 years ago would have felt the same, right?

That’s exactly what astronomers thought when they proposed this comet as the Star of Bethlehem, something that would make sense and add beauty and symbolism to the story. However, once again, current calculations threw the proposal out the window. It turns out that knowing Halley’s comet was seen in 1986 from Earth and rewinding a bit, we find that, during that time, the closest visits were in 12 B.C. or 66 A.D., which does not coincide at all with the reality.

Later, new reasoning emerged that would have eliminated the option of Halley’s Comet without the need for calculations, such as its simple reputation. In antiquity, comets were a symbol of bad omen, making it even more unlikely that one of them was considered a “divine sign.” Can you imagine the Wise Men following a black cat to reach the manger? It would be something similar.


Another option considered in more detail was that the famous guiding star could have been a supernova. And, I’ll tell you in advance, this is one of the options that has not been ruled out yet. Who would have thought? The Wise Men following the remnants of a dead star. Precisely, a supernova is that: a large explosion accompanying the death of some massive stars. In fact, it fits well with the Christian story because it mentions that the Star of Bethlehem appeared out of nowhere, like a new star, which is precisely what happens with supernovas: they appear out of nowhere when a star ends its days and emit light for a few days or weeks.

What is the downside to this proposal? It has not been ruled out… because it cannot be refuted. For astronomers, it is practically impossible to know if a star died 2024 years ago (or even much earlier, as light takes a certain time to reach Earth) and if its light reached Earth with much or little intensity. To make matters worse, the first scientific record of such events dates back to 186 A.D., by Chinese astronomers. So, for now, it seems impossible to know if there was an undetected event before that time.


However, the most reliable option to this great dilemma is that the Star of Bethlehem was none other than Sirius, a very bright star that usually appears in the sky during the last days of December. In fact, at that time, Sirius and the Moon are precisely the two brightest points in the entire night sky. Specifically, Sirius is a star that weighs twice as much as the Sun and has a brightness almost 20 times greater. If you want to find it, just look to the left of Orion’s belt.

Does it sound consistent with the original version, right? Well, if I tell you that Sirius was already a guiding star before, it sounds even better. It served as a guide for many centuries for Northern Hemisphere navigators during dark nights due to its enormous brightness, serving as a reference point for navigating the sea.

Sirius or a supernova? Will we ever know? Maybe not, or even none of them are the correct options, there is another more realistic alternative not yet considered, or perhaps that guiding star never existed, and there is no valid option in the real firmament. Whatever the correct option is, perhaps the most sensible thing is to continue calling it by the name that made it famous and wait for new astronomical revelations: The Star of Bethlehem.


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