Many people have attempted to give an astronomical explanation for the star of Bethlehem. How one interprets the story told in St. Matthew's Gospel depends to a great extent on one's religious beliefs, cultural background and, to a lesser extent, one's scientific knowledge.
It is instructive for the reader to go back to the original account in St. Matthew's Gospel (Matthew chapter 2, verses 1-12) to see what is included and what has come down to us as interpretation or embellishment. For example, there is no mention of there being three kings, only 'Magi' (wise men, magicians or possibly astrologers) who left three gifts. The Greek word generally translated 'star' (αστερα - astera/astra from which we get 'astronomy') can also mean planet and could refer to other objects such as a comet. There is no mention that the star was particularly bright, nor does it seem to have had any significance for anyone other than the Magi.
There is also little indication that the 'star' alone led the Magi to Bethlehem. Initially they came to Jerusalem and were directed to Bethlehem by Herod, acting on biblical references regarding the Messiah's prophesied birthplace. However, Matthew's account does state that 'After they had heard the king [Herod], they went on their way, and the star they had seen in the east went ahead of them until it stopped over the place where the child was.' (Matthew chapter 2, verse 9)
Modern interpretations of the biblical story range from acceptance of it as literal truth to assertions that it is pure fiction.
Purely supernatural explanations for the star are beyond the remit of this article, but could include angels, a heavenly vision, or a divine light like the guiding 'pillar of light' described in the Biblical book of Exodus. Paranormal but non-supernatural explanations such as a UFO have also been put forward for the star.
Another important strand of possible explanation for the star is astrological, which again is outside the remit of this article. The Magi are thought by many to have been astrologers and the significance of the 'star' for them may have been primarily astrological rather than astronomical. For example, the astronomer Michael Molnar has recently suggested that a double occultation of Jupiter by the Moon in Aries in 6BC may astrologically have signified the birth of a divine king of the Jews.
At least six purely astronomical explanations for the star of Bethlehem have been put forward:
- Conjunction of Jupiter and Saturn
- Close grouping of Jupiter, Saturn and Mars
- Stationary point of Jupiter
- Variable star
It is difficult at first to see how any of these could qualify as a miraculous event. However, this was not apparently an issue for early Christian thinkers like Origen (c.185–254) or later theistic scientists such as Kepler (1571-1630). The idea that a supreme deity who orders and maintains the universe can use 'natural' events to serve divine purposes has a long theological history.
This theory, that the Magi saw a nova or supernova explosion, was hinted at by Kepler and has had many supporters since then. However, there is no western record of such an event and the Chinese records, which would be expected to include such an object, only have a possible record of a nova or comet in the spring of 5 BC (when many scholars believe Jesus was born).
There is also no known supernova remnant, which we would expect to find if there had been a supernova at the birth of Jesus.
However, it's possible that it may have been a nova outburst associated with a variable star.
This has its origins event further back in time, dating to AD 248 when Origen invoked it as an explanation. Again the Chinese records can be invoked but give no good support apart from the 5 BC nova/comet. Much play has been made of the statement that the star stood over the city for days. Comets often have tails and these can be imagined to point towards or away from any point near the horizon. This would of course be true of any city when viewed from the correct vantage point.
One advantage of the comet theory is that comets move across the starry sky. It has been argued that this fits the interpretation of the Gospel that the star was first seen in the east and thereafter moved to the south. The same argument could be applied to an object moving with the stars, however, if the journey of the Magi took some months.
Most classical depictions of the nativity show the 'star' as a comet.
Kepler is also associated with the idea that the close conjunctions of Jupiter and Saturn were the event associated with the 'star'. In fact there were three conjunctions, when the two planets were close to one another in the sky, but none of these were close enough that the two planets would appear as one object. For this reason most analysts have rejected this theory. Nonetheless, such an event could have been of religious or astrological rather than astronomical significance to the Magi, particularly if combined with another event such as a nova or bright star.
In 6 BC, these three planets were fairly close together in the constellation Pisces. However, the planets only got within about 8° of one another and it seems unlikely that this would have been called a 'star'.
Jupiter, in its apparent path across the night sky, is generally seen to move from east to west across the starry background. Due to the relative movements of the Earth and the planets this motion appears to slow and then stop as the planet reaches what is called a stationary point. The planet then appears to move from east to west for some days before again stopping and resuming its west to east movement. At the time of the birth of Christ one of the stationary points could have occurred when Jupiter was directly overhead at Bethlehem at the same time of night for several nights.
The disadvantage of this explanation lies in the lack of any rarity in the phenomenon as it would happen every year and has to be linked to another astronomical phenomenon such as the appearance of a comet.
The British astronomer Mark Kidger has recently proposed a new idea for the Bethlehem star. He suggests that the object was actually a real star that can still be seen with telescopes today: a now rather dim object known as DO Aquilae. This is a variable star i.e. one that changes its brightness and which may have experienced a nova outburst in the past. Note that the material thrown off by a nova would be very hard to detect after the passage of 2000 years.
In the year 5 BC when many scholars believe Jesus was born, a combination of a bright nova and a triple conjunction of Jupiter and Saturn in the constellation of Pisces was seen. Ancient Chinese astronomers recorded this as an unusually bright star that appeared in the eastern sky for 70 days. This was a rare sight and the Magi may have believed the combination of the two events was a religious sign.
An alternative view with some substance is that the inclusion of the star is an example of 'Midrash', a Judaic tradition of scriptural interpretation and of writing about scriptural themes.
In Midrash, details do not have to be historical and the inclusion of legendary or non-factual elements may be used to accentuate the religious meaning of the factual account. This does not mean that the author of Matthew's Gospel invented the story of the star but that he knew of traditions concerning Christ's birth and incorporated them into his account so as to convey to the reader the miraculous way in which Christ was born. His aim would have been to convey the good news of salvation i.e. the 'gospel'. The story of the Magi, and particularly the appearance of the star, could then be an illustrative or metaphorical representation intended to demonstrate the fulfilment of various Old Testament prophecies in the birth of Christ, and the star could also be a way of representing the 'glory' of God made visible in Christ. The most significant Old Testament prophecy for this is Balaam's fourth oracle in the book of Numbers: 'A star will come out of Jacob; a sceptre will rise out of Israel' (Numbers chapter 24, verse 17, emphasis added).
The fact that the author of Matthew's Gospel was writing in a Hebraic environment and for a largely Jewish audience gives further credibility to this explanation.
None of the possible astronomical explanations appears to have overwhelming evidence to indicate that it should be preferred to any of the others, though some (nova, comet, variable star) appear more likely than others (conjuction of Jupiter and Saturn, stationary point of Jupiter).
On the face of it, there appears to be little to distinguish between the three classical explanations that the star was a supernatural event, has a scientific explanation or was pure fiction (or at least symbolic reinterpretation); and of course it is possible that it was a combination of the three.
However, the view that the star is an example of 'Midrash' is worthy of consideration, and provides a plausible explanation for the Star of Bethlehem.
Produced by: Dr Peter Andrews, Institute of Astronomy, University of Cambridge.
Updated on: 11 January 2001 by Robert Massey, Royal Observatory, Greenwich.
Last updated on: 16 December 2009 by Harvey Edser, Web Editor, NMM.