Early Astronomy in the University of Michigan Collections

On Sunspots

The publication of Galileo’s Sidereus Nuncius (The Starry Messenger) inspired other European astronomers to explore the skies with equally powerful telescopes. The German Jesuit priest and mathematician, Christopher Scheiner, directed his attention to the Sun, discovering various sunspots in 1611. As a member of a fairly conservative community of Jesuit scientists, Scheiner tried to reconcile Aristotelian cosmology with the result of his solar observations. Thus, he aimed to keep the “perfection” of the Sun, and of the heavens, by arguing that these recently observed sunspots were in fact optical reflections caused by satellites of the Sun, whose shadows were projected to the disk of the Sun as they traveled in front of it. His treatise, Tres epistolae de maculis solaribus (Three Letters on Sunspots), was published under the pseudonym, “Apelles hiding behind the painting”, in Augsburg in early 1612. These three letters were addressed to Marc Welser, a wealthy banker and scholar who supported the scientific endeavors of the Jesuits. Welser asked Galileo his opinion about Scheiner’s tract, and Galileo replied with two letters to Welser, challenging the idea of the Sun’s perfection by showing that sunspots were irregular bodies that originated, and perished, near or on the surface of the Sun. Meanwhile Scheiner had written two more letters on the same topic, adding another one upon reading Galileo’s first letter. This new installment of three letters was published, again under the pseudonym of Apelles, by Welser in Augsburg in the Fall of 1612: De Maculis solaribus et stellis circa Iovem errantibus, accuratior disquisitio (A More Accurate Disquisition on Sunspots and the Stars Traveling around Jupiter).

The title page of our copy bears an ownership inscription of the Jesuit College of Dillingen, a town in southern Germany, dated 1617: Collegii Societatis Iesu Dilingae.1617. There is an early inscription at the bottom of the page, which is hardly legible for having been trimmed by the binder. We can only make up the first two letters: “R. P.”

De Maculis

De Maculis: Engraving


Istoria: Engravings


Select Bibliography

  • Galilei, Galileo and Christoph Scheiner. 2010. On Sunspots. Trans. & introd. Eileen Reeves and Albert Van Helden. Chicago - London: The University of Chicago Press.

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