Colin J. Humphreys , The Star of Bethlehem a Comet in 5-BC and the Date of the Birth of Christ, , The Star of Bethlehem has been considered either to be mythical or a miraculous object beyond the bounds of scientific explanation or a real astronomical phenomenon. The question of whether a celestial phenomenon reported in ancient literature in an historical context was a real astronomical object in one which occurs quite frequently. In all such cases it seems best to consider as a working hypothesis that the report is correct and to investigate whether any astronomical phenomenon exists which fits the report. There are three main characteristics of the Star of Bethlehem recorded in Matthew's gospel. It was a newly appeared star, it travelled slowly through the sky, and viewed from Jerusalem it appeared to stand over Bethlehem. One, and only one, astronomical object satisfies this description: a comet with a long tail. From ancient Chinese astronomical records there was a long-tailed comet in 5 BC which was visible in in the east in the morning sky and appeared for over 70 days. This description fits well the description in Matthew's gospel. It is suggested that a combination of three unusual astronomical events caused the Magi to set off on their journey. First, the triple conjunction of Saturn and Jupiter in the constellation Pisces in 7 BC, which would have symbolised to the Magi that a divine king would be born in Israel. Second, the planetary massing of Mars, Saturn and Jupiter in Pisces in 6 BC which appeared in the east in the constellation Capricornus, signifying to the Magi that a very great king was about to be born. Thus the comet of 5 BC was the Star of Bethlehem, and this marks the date of the birth of Christ and the true BC/AD origin of our calendar. Hence the start of the 2000th millenium has already passed!
Johannes Kepler , Opera Omnia, , Widerholter Außführlicher Teutscher Bericht Das unser Herr und Hailand Jesus Christus nie nuhr ein Jahr vor dem anfang unserer heutiges tags gebreuchigen Jahrzahl geboren sey: etc. (Pauli Ledertz, Strasbourg, 1613) - reprinted in Kepler's Opera Omnia, 4, 201-269 & 510-??? and in Kepler's Gesammelte Werken, 5, 129-201.