Is it a bird? Is it a plane? The science behind The Star of Bethlehem

What was the star of Bethlehem? A quiet debate has been bubbling away for decades between astronomers and philosophers alike. Could some real cosmic event have led three wise men on a journey to find a new King? As the story goes, a bright star appeared in the sky upon the birth of Jesus Christ. The “three wise men” followed this star to the place where the child lay, showering Him with gifts of gold, frankincense and myrrh. As children we were all regaled with this, the Nativity story, and were made to perform the play at Christmas time (I’ll never forget my starring role as sheep no. 4). Religious or not, there is something about this story that has inspired millions, not least because it recounts the wonders of the cosmos. As it turns out, countless astronomers tend to agree. A multitude of theories have been proposed as to the exact nature of the star – if indeed it is a star. There is, of course, a huge assumption to be made – that the story of the star and the journey is true. The Bible doesn’t actually mention how many wise men there were or where they came from – the tradition of three wise men came about due to the Bible’s description of three gifts. The wise men are however widely accepted to have been religious scholars known as the Magi. These were revered astronomers and astrologists probably from Persia (Iran) or Babylon (Iraq). They studied the stars and planets, interpreting the meaning behind cosmic events; anything unusual was considered an omen. The Gospel of Matthew is the only known account of this story. It describes how the Magi saw the star in their own country and so they travelled to Jerusalem to consult King Herod. The King summoned his advisors who told him that according to the prophecy the Messiah would be born in Bethlehem. When they set out on their journey, the star appeared to ‘hover’ over where the child lay. It is generally agreed that Jesus was born sometime between 6 and 4BC and certainly not in December (a passage in Luke refers to sheep grazing in the fields, implying that it must have been spring or summer). In fact, the Catholic Church chose to celebrate Christmas on December 25^th to coincide with the popular pagan festival, Saturnalia, so as not to draw too much unwanted attention. Historical records show King Herod to have died early in 4 BC, placing the birth of Jesus before then. We are therefore looking for a rare astronomical event that occurred within this timeframe and that could have prompted the Magi to set out on their journey. The problem of the star is twofold: astronomical and astrological, i.e. what was the star and what would have led the Magi to associate it with the birth of Jesus? One of the earliest and most favoured theories, which dates back to 2AD, was proposed by the Christian theologian Origen. He suggested that the star described in the gospel of Matthew was a comet. Comets are essentially big, dirty snowballs that fly through space. When they come close to the sun, the ice melts and is blown away by the solar winds, giving the appearance of a tail. In March/April of 5BC, a group of Chinese astronomers observed a bright comet that appeared in the constellation of Capricorn and was visible for over 70 days. This certainly fits the timeline and calculations show that it would have appeared low in the southern sky as seen from Jerusalem, with the head of the comet close to the horizon and the tail pointing vertically upwards. It’s not surprising that this is such a popular theory, with the comet’s glowing star-like head and long tail pointing prophetically towards the sky like some cosmic finger. Hence, this image is widely depicted in paintings and on Christmas cards. However, the biggest snag in this theory is that comets are not rare, especially to seasoned stargazers like the Magi. As far as omens are concerned, it doesn’t get much worse; comets were known to represent the four D’s: doom, death, disease and disaster. Not exactly the best sign for the birth of a new King and Saviour. So, that essentially rules out that theory. On to the next. Perhaps the simplest explanation is a nova or supernova outburst. Although their names imply the creation of something new, they are, in reality, the products of a nuclear explosion at the end of a star’s life. There was indeed a sighting of a new star or ‘nova’, recorded again by Far Eastern astronomers in the small, northern constellation of Aquila in 4BC. At first glance this seems to be a really good candidate for the star of Bethlehem title since most novae suddenly and unexpectedly burst onto the scene, literally overnight, attracting attention from sky conscious people. A ‘new’ star could also have led the Magi to interpret the birth of a ‘new’ King. However, upon closer inspection this theory starts to fall apart. Those that subscribe to this idea say that the star would have been positioned directly over Jerusalem, so not initially visible to the Magi in Persia/Babylon. The nova would rise an hour earlier every two weeks until it was almost exactly due south at dawn. By the time the Magi reached Jerusalem, the star would appear to hover over Bethlehem, apparently pinpointing the location of the new King. But why would the Magi set off for Jerusalem in the first place? It has been proposed that another ‘omen’ would have been needed for this to happen yet there is no suggestion as to what this might be. This is also in direct conflict with passages in the Bible that state: “we have seen his star in the east”, Matthew 2:2. Further to this, novae lack the astrological significance that planetary movements and conjunctions held for the ancients. Speaking of planetary movements… As the planets dance around the sun in their orbits, from time to time two or more planets will appear to approach each other and then separate again. This is known as a planetary conjunction. It is a trick of the eye from our earthbound perspective since the planets are actually still separated by millions of kilometres. Many astronomers believe that a conjunction of this kind would give rise to a remarkable sight that could explain this majestic star. David Hughes, who lectured in astronomy at the University of Sheffield, has spent many years studying the astronomical explanations and reviewing the Biblical stories. He thinks the best explanation is a triple conjunction between Jupiter and Saturn, which occurred around 7-6BC. These two planets came very close together three times over a short period of time, at which point there was an alignment between the sun, Earth, Jupiter and Saturn. Since the Earth orbits the sun quicker than the other planets, it seems to ‘overtake’ them, making it look like Jupiter and Saturn either stop or go backwards for about 100 days. This is known as retrograde movement. This conjunction occurred in the constellation of Pieces, which had a special meaning in ancient Persian astronomy. It was the sign of Israel and of kings. Jupiter was the royal planet and Saturn represented old rulers. The triple conjunction was noted first in May 7BC looking east from Persia/Babylon, then in Sept/Oct looking west over Jerusalem and finally in December looking south directly over Bethlehem if you were in Jerusalem. A triple conjunction like this would only happen every 800 years and so this would have been a sign of something very significant to the Magi. There are ancient records that suggest the Magi knew of this conjunction. Sounds perfect, right? Yet again there’s a problem. We’re beginning to see a pattern here. Lots of analysts reject this theory because Jupiter and Saturn never really became so close that they could be seen as one object. There was also a similar conjunction of these planets in 66BC, which would have brought the three wise men to Bethlehem 60 years too soon. Also, each of the three conjunctions only lasted a few days, yet the star guided the Magi through a journey of several weeks. At this point you’ve probably lost faith in there being any real explanation for the most famous of all stars. But perhaps we have been searching in all the wrong places. If we are to take the word of the only known account given in St. Matthew, then what we really need is the appearance of not just one, but two ‘stars’. The most convincing theory has been popularised by astronomer and TV presenter Mark Thompson. Between September 3BC and May 2BC there were three conjunctions where Jupiter passed by the star Regulus and exhibited retrograde motion. Thompson found that Jupiter passed Regulus in an easterly direction before it seemed to reverse, passing the star again in a westerly direction. This continued for several weeks before changing direction again and continuing its easterly drift. Thompson told The Telegraph: “the retrograde motion meant the planet was travelling in a westerly direction in the sky and so the [three wise men] may have followed it from Persia. By camel it would have taken about three months and interestingly this is roughly about the same time Jupiter was travelling in the westward direction.” That’s the astronomy part taken care of but what is the astrological significance? Regulus is the star of kingship and is the brightest star in the constellation Leo. Leo is also the constellation of Kings and is associated with the ‘Lion of Judah’. In Arabic, Regulus is often known as Qalb al-asad, i.e. “the heart of the lion”. These signs all clearly point to a Jewish King. A group of researchers at Indiana University noted that there was a spectacular conjunction between Jupiter and Venus about a month after Thompson’s timeline. Both planets are thought to have overlapped in the night sky on June 17, 2BC, making them indistinguishable to the naked eye. Could Jupiter have led the three wise men across the desert to Bethlehem after its bizarre change of direction, culminating in a dazzling conjunction with Venus? Planets this close can be striking, if they don’t differ too much in brightness. Venus is the planet of fertility; couple this with the Regulus/Leo foretelling of a King of the Jews and there you have it – the Nativity has been predicted. Incidentally this sign would have been seen in the east by those who reside in the east, clearing up any ambiguity in those foggy Bible passages in the gospel of Matthew. There has not been a brighter, closer conjunction of Venus and Jupiter in Leo so near to Regulus in the 2000 years since. So it seems that this theory wins the title and is crowned the ‘star of Bethlehem’. We may never know if the star of Bethlehem was a real celestial object or just a story to inspire but we can be sure that astronomers will continue to debate this enigma for as long as the Nativity story lives on. For now, I’ll let you decide. Author Rebecca Dey is an Editorial Intern at Laboratory News and is currently undertaking a PhD in Polymer Chemistry at the University of Manchester.