For 400 years, astronomers have tried to explain the celestial phenomenon that attracted the Magi to the birth of Jesus. Johannes Kepler, the pioneer of modern astronomy, was the first to analyze it in 1614. Now, scholars increasingly agree that Michael Molnar, a former Rutgers University astronomer with a coin-collecting hobby, may have figured it out.

Molnar’s research was debated by scientists, theologians, and historians during a colloquium on the Star of Bethlehem at the Netherlands’ University of Groningen this October. The conference marked 400 years since Kepler published his famous treatise on the star.

Initially, Molnar did not have a particular interest in the topic, though he would describe the various theories to inquisitive students at Christmastime. But one day, an ancient coin he purchased for his collection gave him a new clue.

The coin, minted in Antioch in the early 1st century, depicted a ram looking at a star. As Molnar investigated the symbolism, he found evidence that Aries the Ram—not Pisces the Fish, as is commonly assumed—was the zodiac symbol for Judea.

"What I had in my hands was evidence that modern researchers really had to rethink their explanation about the star," said Molnar.

Combing ancient astrological documents, he found not a bright object but a rare conjunction that would have gotten the attention of the Magi.

Astrologists associated the planet Jupiter with royalty. So if the moon passed in front of Jupiter (called an "occultation") while in Aries the Ram, it would have royal significance. Molnar found two dates in 6 B.C. when such occultations happened. Then, reading the text of Matthew 2, he realized the Greek word for “in the East” was the astrological term for a planet becoming a morning star.

"I was amazed to find April 17, 6 B.C., was exactly when Jupiter was 'in the East,' a morning star," he said. "So I knew I had an answer to the Star of Bethlehem."

Harvard astronomer Owen Gingerich, who opened the conference, supports Molnar’s explanation but noted the conference raised many technical questions. “It is being fairly widely accepted,” he said, "but not necessarily all of the details." For example, many astronomers are not convinced Aries the Ram symbolized Judea.

But a growing consensus confirms that the Star of Bethlehem was not a bright object, like a supernova or a comet, as others have argued. "The gospel story is one in which King Herod was taken by surprise," said Gingerich. "So it wasn’t that there was suddenly a brilliant new star sitting there that anybody could have seen [but] something more subtle."

"From our modern point of view, it was not very impressive," said Molnar. "It must have been spectacular from their point of view."

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