What Was the Star of Bethlehem?

Three charts of the sky over Babylon, one for each night people have proposed. One theory’s sky each, not a claim that this was the night.

Matthew tells it briefly. Magi came from the east to Jerusalem, asking:

“Where is the One who has been born King of the Jews? We saw His star in the east and have come to worship Him.”

(Matthew 2:2)

He never says what the star was. People have asked ever since, and the honest answer is that nobody knows. What we can do is read the record, work out the sky, and see which nights fit.

First, the calendar

Most of us carry a picture of the first Christmas as 25 December, AD 1. Neither half of that comes from the Bible.

The year. Our count of years goes back to Dionysius Exiguus, a monk in Rome. In AD 525 he drew up a table of future Easter dates and numbered the years from the incarnation of Christ instead of from the reign of a persecuting emperor. He wrote about five centuries after the events, and he did not explain how he fixed his starting point.

Herod. Matthew places the birth “during the time of King Herod” (Matthew 2:1), and the family comes home from Egypt only “after Herod died” (Matthew 2:19). The historian Josephus, writing near the end of the first century, records an eclipse of the moon on the night Herod had a rebel named Matthias burned alive, and Herod’s death some time later. NASA’s eclipse catalogue lists a partial eclipse of the moon on 13 March 4 BC, and most historians place Herod’s death soon after it. If they are right, Jesus was born before 4 BC, and the count Dionysius started runs a few years late.

Herod’s order against the boys of Bethlehem “two years old and under” (Matthew 2:16) also suggests the Magi arrived some time after the birth. The star need not have appeared on the night itself.

No year zero. The count runs from 1 BC straight to AD 1. It matters when you subtract: from 2 BC to AD 2 is three years, not four.

The day. The two gospels that tell the birth give no day and no month. One of the earliest records of 25 December is a Roman church calendar compiled in AD 354, which lists against that date the words natus Christus in Betleem Iudeae: Christ born in Bethlehem of Judea. It is a tradition the church has kept for well over a thousand years. It is not a date the gospel writers recorded.

Three nights that fit

Each theory below fits part of the evidence. Only one can be right, and it may be none of them.

7 BC: Jupiter and Saturn, three times

Why it fits. In 7 BC Jupiter and Saturn passed each other three times in one year, in late May, early October and early December, each time in the constellation Pisces. Herod was alive. Johannes Kepler watched the same two planets meet in 1603 and saw a new star appear in 1604. He worked back, found the triple meeting of 7 BC, and proposed that the Star of Bethlehem belonged to it.

The caveat. The planets never merged. At each pass they stayed about a degree apart, roughly two widths of the full moon. Two bright lights side by side is a striking sight, but Matthew speaks of one star.

5 BC: the broom star

Why it fits. The official history of the Han dynasty in China records that in the second month of the second year of the Jianping reign, a “broom star” appeared in the part of the sky called Qianniu and stayed more than seventy days. On our calendar that is spring of 5 BC, and Qianniu lies in what we call Capricornus. It is an independent written record of a new light in the sky, kept on the other side of the world, while Herod was alive. The same Han record reads it as a sign that the old is swept away and something new begins.

The caveat. The record gives no brightness and no exact position. A broom star usually means a comet with a tail, and whether this one was a comet or a new star is still argued. Any drawing of it is a reconstruction.

2 BC: Jupiter and Venus as one

Why it fits. On the evening of 17 June 2 BC, Jupiter and Venus drew so close that, seen from Babylon, they sat less than a twentieth of the moon’s width apart. To the eye they would most likely have looked like a single brilliant star, low in the west, the direction of Judea. Several early church writers, among them Irenaeus, Tertullian and Clement of Alexandria, give dates for the birth that are usually reckoned as about 3 or 2 BC.

The caveat. This night needs Herod alive in 2 BC. That means dating his death after a total eclipse of the moon in January 1 BC rather than the eclipse of 4 BC. Some scholars argue for exactly that. Most historians still prefer 4 BC. The verse says the Magi saw His star “in the east”, but on 17 June the pair stood low in the west and was going down.

Looking up

Kepler worked out his skies by hand, from tables and patience. The same arithmetic, done by a computer, drew the charts above, and it can draw the sky over another night and place. We cannot tell you which night the Magi saw. If there is a night of your own you would like to see again, here is the sky over it.