Appendix 6: Works by Johannes KEPLER the Austrian astronomer (1571-1630)  (Written on December 8, 2018)


An emblematic work by Kepler is published in 1606 : De stella nova in pede serpentarii,

If this work does not have the scientific scope of Astronomia nova (1609) or Epitome astronomiae copercicanae (1618 - 1621) where Kepler exposes what is today denominated his 3 fundamental laws on the movement of the planets on their orbit, it shows the characteristic of Kepler's personality, at once a famous astronomer and a convinced astrologer. For him, astronomy (astronomical observation) and astrology (supposed correspondences with human affairs) were linked but he was very critical about popular astrology.

(Kepler's 3 laws on planetary motion:


The years 1603 - 1604 are marked by an important event for astronomers of the time: a conjunction Jupiter - Saturn. And in this direction, appears a new star that could be observed from October 1604 to October 1605. Kepler then multiplies the observations and the measurements, then compiles the data in De stella nova ... The precision of his work is remarkable for the time and allowed, much later in the 20th century, the identification of this famous star : it was a supernova terminally explosive.

But for Kepler, such an astronomical event (a supernova associated with a triple conjunction of Jupiter and Saturn) can not be devoid of meaning. He associates this phenomenon with the star of the Three Wise Men and, taking up the historical arguments of Laurent Suslyga, Kepler establishes by astronomical calculations a new date for the birth of Christ : -5 before our era. He records his results in a pamphlet - De Jesu Christi Servatoris vero anno natalitio, consideratio novissimae sententiae Laurentii Suslygae Poloni, quartet annos in usitata epocha desiderantis ... - which he publishes with De stella nova.

With the improvement of astronomy we have realized that the complete cycle of conjunctions is shorter than what the ancient authors affirmed. Kepler has calculated that this cycle lasts about 805 years.

Cycle of about 805 years.

The completion of a cycle has been considered by Kepler as a marker for events of great importance, such as the creation of empires or the coming of the messiah: Adam, Enoch, Noah, Moses, Isaiah, Jesus, Charlemagne, Rodolphe II.