The famous Star of Bethlehem may not have been a star at all, but an extremely rare planetary alignment, per University of Notre Dame astrophysicist Grant Matthews.

“Astronomers, historians and theologians have pondered the question of the ‘Christmas Star’ for many years,” said Matthews, in a press release. “Where and when did it appear? What did it look like? Of the billions of stars out there, which among them shone bright on that day so long ago?”

After studying historical, astronomical and biblical records, Matthews believes that the event that led the Magi to Bethlehem was a rare planetary alignment that occurred in 6 B.C. During the alignment the sun, Jupiter, the moon and Saturn were all in Aries while Venus was next door in Pisces and Mercury and Mars were on the other side in Taurus. At the time, Aries was also the location of the vernal equinox.