David Wagle's brother-in-law wrote this in 1993. His brother-in-law worked at CTIO at the time. AT URL: http://listserv.american.edu:70/1/catholic/other/wise.men there is this excellent response: There are several theories concerning the Star of Bethlehem. There are many possibilities due to the ambiguity of the descriptions in the Gospel of St Matthew and also to the looseness of the general descriptions of astronomical objects at the time. To complicate matters, we also do not know exactly when Christ was born. The basis of scientific explanations relies on several characteristics of the star as described in the Gospel of St Matthew: a) It was a star which had newly appeared. However, the Matthew not remark that it was unusually bright. Although it was significant for the Magi, Herod did not mention seeing it. b) The star was referred to as a single object. c) The star "went before" the Magi, which from the original text is equivalent to saying that the Magi "followed" the star, or kept it under observation. (However, it did not necessarily lead _towards_ Bethlehem.) d) The star "stood over" Bethlehem. It is important to consider several other pieces of background information. The Magi: The Magi are thought to be a priestly group in the Persia-Babylon region who became associated with astronomy and astrology. There was a strong Jewish colony in Babylon which was familiar with Biblical prophecies. The Magi probably knew of the prophecy of a Messiah. The journey time from this area to Jerusalem is thought to be 1 - 2 months. The date: A calculation of the birth of Christ was made in AD 525 by Exiguus, a Roman monk. He failed to include a year 0 and also omitted four years of Caesar Augustus' reign under Augustus' given name, Octavius, so his calculation is at least five years too late. A variety of supporting evidence (such as the reign of Herod, who died in 4 BC and details of Roman censuses) indicates that between 5 and 7 BC is considered to be the most likely time for Christ's birth. The sky: There was a triple conjunction of Jupiter and Saturn in Pisces in 7 BC. A conjunction is when two planets appear very close together. As Earth approaches, overtakes and then advances beyond these planets, which move more slowly in their orbits than does Earth, it is possible that such a phenomenon could be seen three times within a span of several months. Such an event only happens about once every 900 years in Pisces and was predicted by the ancients. Pisces is astrologically associated with the Jewish people and with Israel. Jupiter was considered to be a lucky and royal "star" and in traditional Jewish astrology Saturn protected Israel. Thus, such an event would have been interpreted as having great astrological significance. There was also another predicted celestial event: the grouping of Mars, Jupiter and Saturn within 8 degrees of each other in Pisces in February of 6 BC. Such an event, which occurs only every 800 years, also could have been taken as an important astrological sign, and raised expectations for a third sign in the sky. Based on the astrology at the time, it could have been interpreted by the Magi that a mighty king was to be born in Israel. Theory 1: A nova in March-April of 5 BC. A nova is a white dwarf (an old, shrunken star which has used up its nuclear fuel) which is in a close, mutual orbit with a larger star. The white dwarf pulls material off from its partner star. >From time to time, enough material accretes to provide sufficient pressure for a thermonuclear explosion, causing an increase in brightness of the white dwarf by up to a factor of 50000. Chinese astronomers recorded a new star in Capricorn in March-April of 5 BC which was visible for over 70 days. This object would have appeared in the east several hours before sunrise. It is unclear whether this was a comet or a nova. No motion was recorded. A rayed appearance could have arisen from distortions within the human eye for a sufficiently bright object. There is no record of the brightness of the star, but a typical nova which is visible to the naked eye could be seen for as long as seventy days, about the journey time of the Magi. Capricorn is in the direction of very few stars in our Galaxy, so the probability of a nova in that direction is low. The astronomer Foucquet in 1729 proposed that the star was a nova, although there is evidence that the German astronomer Kepler first suggested the idea in 1614. The hypothesis is still under debate today. Theory 2: A comet in March-April of 5 BC. Comets in antiguity were regarded as heralding important events. The Chinese called comets "broom stars" on the account of their tails, and thus they have been associated with "sweeping away the old order of things." The same "new star" described by the Chinese astronomers in 5 BC might not have been a nova, but instead could have been a comet. Such an object could travel slowly against the background stars, and also be visible for up to several months. It is suggested that the Magi originally saw the object in the east in the morning sky. A month or two later, when the Magi went from Jerusalem to Bethlehem, they then would have seen the star ahead of them (to the south). It is quite possible for a comet to travel 1 - 2 degrees per day in order to swing 90 degrees from east to south during the journey of the Magi. Halley's comet made an appearance in 12 BC but this is outside the range of probable dates for the birth of Christ. The first recorded connection of the star with a comet is from the monk Origen c. AD 248, and the theory is still open to debate. Theory 3: A planetary cause. The Magi would have predicted the triple conjunction of 7 BC and realised its significance. During the first encounter of the triple conjunction in late May of 7 BC, when Jupiter and Saturn were two Moon widths apart, the Magi could have set out upon their journey. The second encounter of the triple conjunction in late September would have appeared as they reached Jerusalem. The third encounter, in early December after a presumed audience with Herod, would have appeared in the south towards Bethlehem. However, in this conjunction Jupiter and Saturn were never close enough together to be confused as a single object. The Jewish astrologer Masha'allah c. AD 800 proposed the star to be associated with the conjunction, and today there is still active debate on the subject. A variation of this theory proposed in 1992 by the British academic Bulmer-Thomas is that the star simply was the planet Jupiter passing through a stationary point as viewed from Earth. This arises from Earth catching up with and then overtaking Jupiter, as Earth travels more quickly in a smaller orbit around the Sun than does Jupiter. The giant planet would appear to stop, move backwards for a time, stop again, and then move forward in its usual direction. The stationary points appear to last for about a week as judged by the human eye. There is abundant evidence from hundreds of cuneiform texts that such motions were of keep interest to Babylonian astronomers of the time. The Magi in their journey from the east to Jerusalem and Bethlehem were simply observing the motion of the planet, and were at Bethlehem when Jupiter arrived at a stationary point. To strengthen the case for the star being Jupiter, the Greeks and Romans both used the word "Saviour" in reference to Jupiter. The Greek word for "above" used in St Matthew's Gospel is a very general term, and could just mean that the star was somewhere in the sky above Bethlehem. The triple conjunction of 7 BC and the grouping of Mars, Jupiter and Saturn in 6 BC would have alerted the Magi to look for a further sign in the sky. If they were to follow Jupiter from the time it emerged from behind the sun in May of 5 BC, four months later (consistent with their journey time) they would have seen it pass through a stationary point. The date would be consistent with other biblical information. The ambiguity of the ancient astronomical descriptions and the uncertainty in the date of Christ's birth make it difficult to judge the true nature of the Star of Bethlehem. I would consider the nova in 5 BC theory somewhat unlikely considering that its location in Capricorn is some 40 degrees from the plane of the Milky Way, which is where most novae are observed. Such an object also would not move with respect to the stars, although in the Gospel it is unclear whether the star actually did move. The comet theory allows for movement, but the Chinese did not record any such motion for the new star of 5 BC. It is difficult to ascribe the star to the conjuction of Jupiter and Saturn as they were never close enough to be seen as a single object, while the Gospel never mentioned any multiple nature for the star. The hypothesis that it was Jupiter passing through a stationary point has difficulty in explaining that it was a new star -- rather, Jupiter was well known. However, St Matthew wrote that Herod asked the Magi "when the new star appeared" (Mt 2:7). This could have been simply in reference to Jupiter's arising from behind the Sun. This would make Jupiter the most straightforward explanation for the event, especially in light of its astrological significance. Lastly, it is possible that the star grew out of legend. No king of any note in that time was born without some celestial manifestation. St Matthew, writing for a Jewish audience, may have felt that a star was necessary to fulfill a prophecy from the Old Testament (Numbers 24:17). He did not add the typical phrase "that it might be fulfilled" in reference to the star, which weakens its case as a historical fact. Whatever the explanation for the Star of Bethlehem, or whether it even existed or not, it does not take away from the theological mystery of the Christmas story. Little did St Matthew know that his description of the star would keep astronomers and historians busy for 2000 years. To summarise points 2-9: 2) The star could have been a nova, a comet or a manifestation of the planet Jupiter or Jupiter-and-Saturn. Halley's Comet appeared in 12 BC, which is too early to agree with other biblical information. The best estimate for the birth of Christ is 5 - 7 BC. 3) The theories all have early origins: nova (1729), comet (c. AD 248) and planetary conjunction (c. AD 800). 4) The uncertainty in the date for Christ's birth leaves open many possibilities for astronomical explanations for the Star of Bethlehem. 5) It is not explicitly written that the Star of Bethlehem moved with respect to the other stars. If it was a comet or a planet(s), the biblical reference to the word "above" is not precise, so the star could have been anywhere in the sky above Bethlehem. 6) A nova is the flare-up of a white dwarf which has accreted enough material from a companion star to cause a thermonuclear explosion from time to time. 7) Uncertainties in the times of Herod's orders to kill all boys under two years of age, the Holy Family's stay in Egypt, the death of Herod and for which census Joseph went to Bethlehem make it difficult to fix the date of the birth of Christ. 8) None of the theories really stand out as more convincing than the others, although the idea that Jupiter was passing through a stationary point is the most straightforward explanation in that it does not invoke any unknown objects. REFERENCES: Bulmer-Thomas, Ivor 1992, Quarterly Journal of the Royal Astronomical Society, Vol. 33, p. 363 Clark, David H., Parkinson, John H. and Stephenson, F. Richard 1977, Quarterly Journal of the Royal Astronomical Society, Vol. 18, p. 443 Hughes, David W. 1976, Nature, Vol. 264, p. 513 Humphreys, Colin J. 1991, Quarterly Journal of the Royal Astronomical Society, Vol. 32, p. 389