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The Star of Bethlehem

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 to see what is included and what has come down to us as further interpretation or embellishment. For example, there is no mention of there being three kings, only that they left three gifts. The Greek word which is generally translated as 'star' can in fact 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 no indication that the 'star' led the magi to Bethlehem; in fact it was Herod who directed them there acting on biblical references.

Modern interpretations of the biblical story range from acceptance of it as literal truth to assertions that it is pure fiction.

Many discussions of possible astronomical explanations for the star of Bethlehem have been made. In the opinion of the writer of this pamphlet none of these explanations is satisfactory but they are summarised below. The 'true' explanation of the star will almost certainly never be ascertained but in my opinion the explanation that the star is a Midrash is the most likely explanation.

A Midrash means a free form of narration in which details are not necessarily historical and the inclusion of legendary elements is allowed. The tradition, in fact, expects such additions to be made to accentuate the religious meaning of the factual account. This does not mean that Matthew 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'.

Possible astronomical explanations of the star

There are at least six possible suggestions for astronomical explanations:

Nova or new star

This theory, that the magi saw a nova or supernova explosion, was hinted at by Kepler and has had many supporters since then. 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.

There is no known supernova remnant, which we would expect to find if there had been a supernova at the birth of Jesus.


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.

Conjunction of Jupiter and Saturn

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.

Close grouping of Jupiter, Saturn and Mars

In 6 BC, these three planets were fairly close together in the constellation Pisces. The planets only got within about 8° of one another and it seems unlikely that this would have been called a 'star'.

Stationary point of Jupiter

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.

Variable star

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 B.C. 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.


None of these possible explanations appears to have overwhelming evidence to indicate that it should be preferred to any of the others. It is difficult to see how any of them fulfils St. Matthew's idea that this was a miraculous event. There appears to be little to distinguish between the three classical explanations that the star was:

  1. pure fiction
  2. has a scientific explanation
  3. a supernatural event

The suggestion, given above that it was a Midrash seems to the author as likely an explanation as any.

Produced by Dr Peter Andrews, Institute of Astronomy, University of Cambridge.

Last updated 11 January 2001. Dr Robert Massey, Royal Observatory, Greenwich.

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