December 24, 2007 12:00am

IT’S long been a puzzle for Christian astronomers, and now an American professor thinks he has it figured out.

His quest: discovering what was “the star in the East” that led wise men to Bethlehem.

Indiana theoretical astrophysicist Grant Mathews studied NASA databases to come up with his theory.

He found two supernovas in the right period, but said one was too low on the horizon and the other too dull.

Prof Mathews discounted novas and comets because they were believed in ancient times to be a sign of disaster.

He concluded the heavenly sign at the birth of Jesus was probably an unusual alignment of planets.

And the likely date? April 17, 6 BC, when the sun, Jupiter, the moon and Saturn aligned in the constellation Aries.

Prof Mathews believes the wise men were Zoroastrian astrologers who would have identified the planetary alignment in Aries as a sign a sign a powerful leader was born.