Testing Kepler's Hypothesis on the Star of Bethlehem: A Kinematic and Astronomical Analysis of the 7 BCE Jupiter-Saturn Conjunction

Abstract

This paper presents an interdisciplinary analysis of the "Star of Bethlehem" narrative described in the Gospel of Matthew (Mt 2:1-12), examining the hypothesis, originally proposed by Johannes Kepler, that the reported phenomenon may be associated with the Jupiter-Saturn conjunction of 7 BCE. The methodology is based on a systematic comparison between the textual account and independently verifiable astronomical data, including retro-calculated ephemerides, sky geometry from Judea, constraints of the Jerusalem-Bethlehem route, and the historical chronology of Herod the Great. The narrative elements are treated as distinct, partially independent constraints required to be jointly satisfied within an explicitly falsifiable framework, under restricted observational and kinematic conditions, avoiding arbitrary parameter choices. The analysis indicates that the 7 BCE Jupiter-Saturn conjunction-characterized by its triple occurrence and extended duration-exhibits an apparent motion consistent with key aspects of the reported behavior of the star, including its progression and apparent stopping. In particular, the stationary phase of Jupiter occurs within a few days of an independently identified sky-ground kinematic synchronization window, without ad hoc adjustments. A sensitivity analysis suggests that this compatibility remains stable under reasonable variations of assumptions. The Jupiter-Saturn conjunction thus emerges as a coherent candidate satisfying the constraints considered. This study does not aim to establish a definitive historical identification, but to propose a physical and testable framework for evaluating the compatibility of celestial configurations with the narrative. It highlights a convergence between astronomical data and textual constraints, indicating that the account cannot be dismissed as scientifically incompatible on the basis of rational analysis.