Editing Johannes Kepler (section)

=== Supernova of 1604 ===
{{See also|Kepler's Supernova}} [[File:Keplers supernova.jpg|thumb|upright=.9|Remnant of Kepler's Supernova [[SN 1604]]]]
In October 1604, a bright new evening star ([[SN 1604]]) appeared, but Kepler did not believe the rumors until he saw it himself.<ref>Caspar, ''Kepler'', p.&nbsp;151.</ref> Kepler began systematically observing the supernova. Astrologically, the end of 1603 marked the beginning of a [[fiery trigon]], the start of the about 800-year cycle of [[great conjunction]]s; astrologers associated the two previous such periods with the rise of [[Charlemagne]] (c. 800 years earlier) and the birth of Christ (c. 1600 years earlier), and thus expected events of great portent, especially regarding the emperor.<ref>Caspar, ''Kepler'', pp.&nbsp;151–153.</ref>

It was in this context, as the imperial mathematician and astrologer to the emperor, that Kepler described the new star two years later in his ''[[De Stella Nova]]''. In it, Kepler addressed the star's astronomical properties while taking a skeptical approach to the many astrological interpretations then circulating. He noted its fading luminosity, speculated about its origin, and used the lack of observed parallax to argue that it was in the sphere of fixed stars, further undermining the doctrine of the immutability of the heavens (the idea accepted since Aristotle that the [[celestial spheres]] were perfect and unchanging). The birth of a new star implied the variability of the heavens. Kepler also attached an appendix where he discussed the recent chronology work of the Polish historian [[Laurentius Suslyga]]; he calculated that, if Suslyga was correct that accepted timelines were four years behind, then the [[Star of Bethlehem]]—analogous to the present new star—would have coincided with the first great conjunction of the earlier 800-year cycle.<ref>Caspar, ''Kepler'', pp.&nbsp;153–157</ref>

Over the following years, Kepler attempted (unsuccessfully) to begin a collaboration with Italian astronomer [[Giovanni Antonio Magini]], and dealt with chronology, especially the [[Chronology of Jesus|dating of events in the life of Jesus]]. Around 1611, Kepler circulated a manuscript of what would eventually be published (posthumously) as ''[[Somnium (novel)|Somnium]]'' [The Dream]. Part of the purpose of ''Somnium'' was to describe what practicing astronomy would be like from the perspective of another planet, to show the feasibility of a non-geocentric system. The manuscript, which disappeared after changing hands several times, described a fantastic trip to the Moon; it was part allegory, part autobiography, and part treatise on interplanetary travel (and is sometimes described as the first work of science fiction). Years later, a distorted version of the story may have instigated the witchcraft trial against his mother, as the mother of the narrator consults a demon to learn the means of space travel. Following her eventual acquittal, Kepler composed 223 footnotes to the story—several times longer than the actual text—which explained the allegorical aspects as well as the considerable scientific content (particularly regarding lunar geography) hidden within the text.<ref>Lear, ''Kepler's Dream'', pp.&nbsp;1–78</ref>