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Hollis Johnson
IU Department of Astronomy

Last modified: Tuesday, December 16, 2003

Star of Bethlehem may have been planets Jupiter and Venus

EDITORS: The following is the fourth of a series of holiday features from Indiana University.

BLOOMINGTON, Ind. -- Early in the evening of June 17, 2 B.C., the brightest planets in the sky, Jupiter and Venus, merged into a dazzling "star" near the western horizon, according to calculations of modern astronomers. In countries to the east of what was then the kingdom of Judea, observers could have seen the fused planets as a beacon in the direction of Jerusalem.

Astrologers associated Jupiter with the birth of kings and Venus with fertility. The meeting of Jupiter and Venus took place in the constellation Leo the Lion, which the Old Testament of the Bible specifically associates with the Jewish people. And it happened near the brightest star in Leo, Regulus, most closely identified with kingship.

There has not been a brighter, closer conjunction of Venus and Jupiter in Leo so near to Regulus in the 2,000 years since.

Could this be the event that caused a group of astrologers called the Wise Men to travel to Jerusalem in search of a new king?

Different views

The Star of Bethlehem is mentioned only in a few verses of the New Testament's Book of Matthew (Chapter 2: 1-12), but it is one of the best-known parts of the Christmas story. A number of astronomers and historians have tried to determine what the unusual sight might have been.

Still there is no consensus. Explanations have been proposed since a suggestion by astronomer Johannes Kepler in the 17th century, but each contribution has seemed to raise as many problems as it solves. Hollis Johnson, professor emeritus of astronomy at Indiana University Bloomington, has collected a number of journal articles and other materials on the subject.

"The question of the star is divided into two parts," Johnson said. "One is astronomical: if a star was reported at the time, what was it? The other is astrological: why did the Wise Men associate the star with the birth of Jesus?"

There are four main suggestions regarding the Star of Bethlehem, Johnson said. One ( is a close approach by Jupiter and Saturn in the constellation Pisces the Fish, which happened three times during 7-6 B.C. These conjunctions were not spectacular, he said, but a triple conjunction is rare and therefore significant to astrologers. A conjunction is a close approach between two celestial objects as seen from Earth. The closer the objects come to each other, the more visually impressive and astrologically significant the event is. This explanation is currently the most popular, because it makes the common assumption that King Herod the Great died in 4 B.C.

The second suggestion ( is the conjunction of Jupiter and Venus in 2 B.C. described above. For this explanation to be true, Herod must have died at a later date than is commonly believed.

The third suggestion ( is an occultation (eclipse) of Jupiter by the moon in the constellation Aries the Ram in 6 B.C., which happened in daylight and would have been hidden by the glare of the sun. This explanation relies on astrological interpretation, with Jupiter perhaps representing the Star of Bethlehem.

The fourth suggestion ( involves something different -- a nova in the constellation Capricornus the Goat, recorded by Chinese observers in 5 B.C. A nova is an enormous explosion at the surface of a star that is similar to a hydrogen bomb explosion, but much more powerful. The star temporarily brightens greatly, which we see as a nova. After a few days the star begins to fade, and after several months it is back to its original brightness, which may be quite faint.

"We don't know how bright the nova was, but it appeared to the ancients to be a new star," Johnson said. A faint nova would have been noticed only by those who studied the sky, such as astrologers. But it would have been significant to astrologers because it was new.

The Wise Men

Apparently the Star of Bethlehem was noticed only by the Wise Men. There is no mention of a star in Luke's description of an angel announcing the birth of Jesus to shepherds in a field. According to Matthew, when the Wise Men arrived in Jerusalem they asked Herod, "Where is he who is born King of the Jews? For we have seen his star in the east and have come to worship him."

Herod had no idea what they were talking about and had to summon his advisers. The advisers told the Wise Men that according to prophecy, the Messiah would be born in Bethlehem.

If the birth of Jesus had been marked by a spectacular event such as a comet, which was considered an omen of great significance, Herod at least would have understood the Wise Men's reference to a star, and the shepherds would have been expecting something extraordinary to happen instead of being surprised.

The astronomical event that excited the Wise Men seems to have been significant only to them. This rules out the possibility of a conspicuous comet. It implies that the Wise Men were astrologers (among other things), for such men would have known how to interpret the appearance of a celestial object that did not attract more than the casual attention of ordinary people.

To provide an astronomical explanation of the Star of Bethlehem, however, it is necessary to know precisely when the Wise Men made their journey to Judea. That turns out to be difficult to determine.

King Herod

The most crucial fact is that Herod was king when the Wise Men arrived in Jerusalem. The difficulty is caused by disagreement among scholars about when Herod died. Roman record-keepers were normally scrupulous, but no specific record of Herod's death has been found. There is considerable indirect evidence that Herod died in 1 B.C. or 1 A.D., but the commonly quoted date for his death is 4 B.C. Scholars writing in the first and second centuries A.D. declared that Jesus was born between what we now call 4 B.C. and 1 B.C. They were living much closer to the event and had access to thousands of historical records.

Herod's death is mentioned in the works of Flavius Josephus, who wrote some 100 years after the event. Josephus stated that Herod died soon after a lunar eclipse, and he wrote in great detail about Herod's funeral. The only lunar eclipse that is consistent with all these details happened on Jan. 10, 1 B.C. According to Josephus, a lunar eclipse in 4 B.C. was the one that preceded Herod's death, and this is why most scholars have assumed that Herod died in 4 B.C. However, copies of Josephus' writings prior to 1552 list 1 B.C. as the year of Herod's death. It is possible that some scribe, toiling by candlelight late at night in 1552, copied the date incorrectly.

See for a detailed discussion of all the historical events surrounding the birth of Jesus.

The birth of Jesus

In September of 3 B.C., Jupiter came into conjunction with Regulus, the star of kingship, the brightest star in the constellation Leo the Lion. Leo was the constellation of kings, and it was associated with the Lion of Judah. Just a month earlier, Jupiter and Venus had almost seemed to touch each other in another close conjunction "in the east" ( Then the conjunction between Jupiter and Regulus was repeated in February and May of 2 B.C.

Finally, on June 17, 2 B.C., Jupiter and Venus, the two brightest objects in the night sky except for the moon, came so close that their disks appeared to touch. This exceptionally rare event could not have been missed by observers such as the Wise Men.

The Bible does not mention how many Wise Men there were or where they came from. (The tradition of three Wise Men developed from the Bible's description of three gifts -- gold, frankincense and myrrh.) It is reasonable to suppose that their journey took months, however, since they had to cross several hundred miles of desert to reach Jerusalem. If they were in Jerusalem before dawn on Dec. 25, 2 B.C., they would in fact have seen Jupiter almost directly over Bethlehem to the south. They could have traveled the five miles to Bethlehem and presented their gifts that day. By then Jesus would have been a child living with his parents in a house, not a baby in a manger. There is a reference not to an infant (brephos in the Greek) but to a toddler (paidion), indicating that the birth itself had been some months before.

That would mean Jesus was born in the spring or summer, which makes a better setting for Luke's account of the shepherds. In winter in Judea it was too cold for sheep to graze in the open fields, and they were commonly kept under shelter during those months, especially at night.

There is no conflict with the traditional date of Jesus' birth, because Dec. 25 was an arbitrary choice. Early Christians changed the date numerous times to avoid discovery by the Romans when persecution of Christianity was at its height. When Christianity finally became the official religion of the Roman Empire, the festival of Christmas on Dec. 25 observing the birth of Jesus replaced the pagan festival on that day celebrating the "rebirth of the sun" as the days began to get longer following the winter solstice.

Designating Jupiter or the conjunction of Jupiter and Venus as the Star of Bethlehem eliminates a number of problems, but probably neither is the last word on the subject. So little is known historically about the period when Jesus was born that new information, such as an archaeological discovery that precisely dates the death of Herod, may well provide a more accurate picture of what happened.