INFERENCE / Vol. 3, No. 2 Homage to Quietanus Jacques Mertzeisen & Jean-Pierre Luminet ne of the stops toward the southern end of the on observations made from Rouffach and addressed to route des vins d’Alsace is the picturesque town Leopold V, the Archduke of Austria–Tyrol.4 of Rouffach, located roughly halfway between Prior to the 1631 transit, observing an event of this OColmar and Mulhouse. The vineyards where the grand nature had posed a number of problems for astronomers. cru Vorbourg is produced lie to the east of Rouffach amid Mercury obscures just 0.04% of the sun’s surface during a the rolling foothills of the Vosges mountains. To the east is transit, and even with the aid of a device such as a helio- the Rhine plain and, on a clear day, visible in the distance scope, which projects the image of the sun onto a screen, beyond, the Schwarzwald. the event is barely noticeable. The first helioscope was A former convent, L’église des Récollets dédiés à sainte invented by Christoph Scheiner, an astronomer and math- Catherine d’Alexandrie, can be found near the ramparts at ematician in Ingolstadt, not long before the 1631 transit. the southern end of Rouffach’s old town. Originally con- Precisely predicting the timing of a transit had also proven structed between 1280 and 1300 following the arrival of problematic. The first to calculate and publish an accurate a Franciscan community some decades earlier, L’église forecast for the transit of Mercury was Johannes Kepler. des Récollets, as is often the case, was embellished and His prediction for the 1631 transit appears in a note he remodeled a number of times over the centuries that wrote two years beforehand, Admonitio ad astronomos.5 followed. Kepler did not live to see the event; he died on November On a wall in the cloister courtyard is a large sundial, 15, 1630. a meter or so in diameter, encircled by a fresco. Dated A successful observation of the 1631 event was thus reli- August 16, 1617, the sundial depicts the solar system in ant on knowledge of both Kepler’s note and the work of a geocentric configuration.1 This was, of course, a time Scheiner—not to mention, of course, a considerable degree when the ideas of Nicolaus Copernicus, published just a of skill and knowledge. The observer in Rouffach, who was few decades earlier, were still contested. But upon closer also the author of the second account, knew what he was inspection, it can be seen that the sun, Mercury, and the doing and how to do it. earth are shown in conjunction, and Jupiter in opposition. That lone observer was Johannes Remus Quietanus. Herein lies a puzzle. It was not until some thirty-five years Quietanus was born Johann Ruderauf on September 22, later, in 1652, that such a configuration could be observed. 1588, in the Thuringian town of Herda. As a young man, How to explain this disparity? And why should such an Ruderauf was enrolled at the University of Jena in 1605, event be commemorated in, of all places, a small town in where he likely studied law and theology.6 In the summer Alsace? of 1607, when Ruderauf was nineteen years old, a comet The answers to these questions, it seems, can be found appeared in the night sky. Its apparition was the inspi- in the story of a little-known seventeenth-century astron- ration for Ruderauf to pen a fifty-page booklet entitled omer, Johannes Remus Quietanus. Gründliche Beschreibung des neuen monstrosischen Sternes Transits of Mercury are relatively rare. Mercury’s orbit welcher Anno Christi 1607 …vom 27 Juli bis helfte october am is inclined from that of the earth and the two planets do hohen Himmel geleuchtet (“Precise Description of a New not move in the same plane.2 For this reason there are Monstrous Star which Shone at the Top of the Sky from 27 only about thirteen every century. The transit of Mercury July to Mid-October in 1607”).7 In it, Ruderauf recorded on November 7, 1631, is particularly notable in the history the trajectory of the comet, noting its day-to-day position of astronomy because it was the first to be predicted and on a map of the sky. His observations are preceded by a observed using scientific methods. Pierre Gassendi, who lengthy preamble proclaiming the comet a sign from God observed the transit from Paris, was long believed to have concerning the Roman Catholic Church and the Republic been the only astronomer to publish an account of the of Venice. The comet was later named in honor of Edmond event.3 But, as it turns out, there is a second account, based Halley, the English astronomer who discovered its period- 1 / 5 SHORT NOTES icity. Halley’s comet has an elliptical orbit that passes close In 1618, Quietanus departed Rome for Innsbruck to take to the sun roughly every seventy-six years, during which up the position of doctor to Maximilian III, the Archduke time it is visible for several months. of Austria. Upon his arrival, he was greeted by Scheiner, A year later, Kepler mentioned the Gründliche Besch- who had been summoned to work for the Archduke. It reibung in a letter to the astronomer Joachim Tancke in was probably Scheiner who introduced Quietanus to solar Leipzig; he had evidently read it.8 observation and the helioscope. At some point between 1607 and 1611 (the precise Maximilian III died in early November 1618.21 Quieta- details are likely lost to time), Ruderauf moved to Padua to nus was subsequently appointed an Imperial doctor and continue his studies. Kepler later wrote that Ruderauf had awarded a substantial pay raise. While Quietanus was now converted to Catholicism during his time in Italy, having doing quite nicely, the outlook for some of his patients was been “in contact with the Inquisition,” and changed his less rosy. In mid-December, the Empress, Anna of Tyrol, name to Johannes Remus Quietanus.9 In Latin, remus qui- passed away. Her husband, the Emperor Mathias I, fol- etanus means “quiet rower,” while the German Ruderauf lowed suit just three months later.22 Quietanus may have designates the oar raised from a skiff.10 been an able astronomer, but as a physician his record At the time, Padua was home to a university with a seems less than stellar.23 renowned medical school. Among those who taught at Quietanus and Kepler resumed their correspondence in the university was Galileo Galilei.11 Writing to Galileo in December 1618. The appointment of Quietanus as physi- 1619, Quietanus reminded him that “I met you in Padua ten cian to Mathias I meant that the pair now had the same years ago.”12 Quietanus was also acquainted with a number employer. In his letter, Quietanus provided an account of of figures from Galileo’s entourage, including Giovanni the recent conjunction of Venus with the moon.24 Reply- Faber, chancellor of the Accademia dei Lincei. According ing on December 1, Kepler congratulated Quietanus on his to Mordechai Feingold’s Jesuit Science and the Repub- new position. In passing, he mentioned a disagreement lic of Letters, Quietanus passed through the College of with Galileo about whether the stars were illuminated Rome.13 by the sun or emitted their own light. Subsequent letters In December of 1611 Quietanus, then twenty-three years between the pair discuss the ban imposed by the Roman old, wrote to Kepler for the first time, from Rome. authorities on Kepler’s Epitome astronomiae Coperni- canae.25 In August 1619, Quietanus sent a copy to Galileo, I have been in Italy for four years and have always carefully who had been unable to find the work in Florence. Also noted the eclipses … [during] my journey [to] Sicily and enclosed was a commentary on the comets of 1618 and Malta, I made some observations to probe the longitudes Kepler’s own assessment.26 Quietanus thus found him- and latitudes of the places, as here also in Rome.14 self serving as an intermediary between the two masters of Copernican astronomy.27 After 1620, the correspon- Quietanus was keen to demonstrate that he had been dence with Kepler lapsed again for the eight years prior to keeping abreast of recent developments—in particular, of Kepler’s announcement of the 1631 transit of Mercury.28 By Kepler’s Astronomia Nova, published two years earlier. this time, Quietanus was already in Rouffach, having set- tled there in the early 1620s. I saw your ingenious work on Stella [the planet] Mars. You In 1624, Quietanus published a calendar, Neuer Schreib- are in agreement with Copernicus in the opinion that the kalender, auff das Jubel Jahr 1625, containing ephemerides, Earth moves. … If this is the case, the fixed stars are very astral charts, and predictions of astronomical and mete- distant since no parallax is observed.15 orological phenomena. Quietanus may, in fact, have published a Schreibkalender each year; traces of ten edi- Quietanus went on to mention the satellites of Jupiter, tions have been found thus far. The annual Schreibkalender recently discovered by Galileo, as well as the precise dura- might have been how Quietanus earned his livelihood. In tion of the equinoctial year. Kepler replied in March 1612, his calendar for 1631, the page for November notes a con- noting that the parallax of the fixed stars is negligible.16 junction of Mercury with the sun, predicted for November Quietanus then appears to have settled in the Holy City 7, with the mention “Such Mercurius under der Sonn” (seek for a time, where he was introduced into papal circles, and Mercury under the sun).