Could This Weirdly Moving Comet Have Been The Real “Star Of Bethlehem”?

The Christmas star. The Star of Bethlehem. Whatever you call it, it is a staple of any nativity scene, just as much as the wise men who followed it, usually represented as a bright star or comet above the stable where baby Jesus lies. The idea of the "star" comes from just a few lines of a single gospel of the Bible; still, it has fascinated people, including scientists, for centuries. Was it a real astronomical event? New research has put forward an intriguing new explanation: a comet with a weird apparent motion.

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In the Gospel of Matthew, the magi (wise men) are described as speaking to King Herod: “There came wise men from the east to Jerusalem saying, Where is he that is born King of the Jews? for we have seen his star in the east, and are come to worship him." It continues: “and, lo, the star, which they saw in the east, went before them, till it came and stood over where the young child was.”

According to the Gospel, the star rose in the sky and appeared to come to a stop, allowing the magi to follow it. However, according to Earth's rotation, everything in the sky rises in the east and sets in the west. 

Mark Matney, a planetary scientist at NASA (though this work is unaffiliated), has identified a possible contender for a real astronomical explanation of the star. However, it's not a star. 

Matney worked out the likely orbit of a comet reported in Chinese annals from 5 BCE. He suggests that the comet ended up in a geosynchronous-type motion, which could potentially explain what the Gospel of Matthew reports. Even without being a Biblical literalist, the comet is fascinating, since it would appear to be stopped still in the sky.   

Let’s place a few caveats before getting into the matter of the new research. First of all, the Gospel of Matthew was written decades after Jesus was supposed to have been born and died, around the year 85 CE, based on a variety of sources. It is also the only one of the four canonical Gospels to mention the star. Originally written in Greek, αστερα was translated as “astra,” meaning star, but maybe it meant another astronomical event or simply an astrological sign that the magi interpreted in a certain way.

The idea of the "star" being a comet is cemented in Christian popular culture due to Giotto di Bondone. In 1305, the Italian artist painted the fresco The Adoration of the Magi. Inspired by his own observation of Halley's Comet during its 1301 passage, the Star of Bethlehem is depicted as a comet. The rest is history, but usually a comet, despite looking a bit like an arrow, is not a good celestial signpost for a direction of travel. 

“A comet has certainly been used to represent the Star of Bethlehem before but as a deliberate marker of direction, it suffers from the same problem as every other object in space does: The constant spin of the Earth means that any object that starts in one part of the sky will inevitably move across it over the course of a few hours,” Dr Greg Brown, astronomer at the Royal Observatory Greenwich in London, told IFLScience in a previous interview.

“The result is that with the exception of the North and South celestial poles (directly above the North and South poles), if you try and walk towards an object in the night sky, you will be constantly changing direction over the course of the day, and it won’t point at any specific place.” 

This is what makes Matney’s calculation interesting. He suggests that a comet with the right orbital motion happened around the right time for the believed birth of Jesus. Even if the star is an embellishment by Matthew, it might have been inspired by a factual event he heard about.

“[I]f an interplanetary object were to travel past Earth at the right speed, direction, distance, position, and time, it would be possible for the motion to temporarily match and counter Earth’s rotation rate. Such an object might appear to temporarily ‘stop’ directly over a particular geographic location for several hours as it passed by,” Matney writes in his paper.

“This is the first astronomical candidate for the Star ever identified that could have had apparent motion corresponding to the description in Matthew, where the Star ‘went before’ the Magi on their journey to Bethlehem until it ‘stood over’ where the child Jesus was.” 

So, a strong contender, maybe, but the Star of Bethlehem holds such a fascination that we are certain this won’t be the last word on the astronomical nature of this object, if it was indeed a real celestial event.

The study is published in the Journal of the British Astronomical Association.