Johannes Fabricius and the Sunspots

A drawing of a sunspot in the Chronicle of John of Worcester.

A drawing of a sunspot in the Chronicle of John of Worcester.

Probably on June 13, 1611, Frisian astronomer Johannes Fabricius published his Narratio de maculis in sole observatis et apparente earum cum sole conversione (Account of Spots Observed on the Sun and of Their Apparent Rotation with the Sun), which counts as the first published description of sunspots. Nevertheless, sunspots have been discovered earlier, as the first record of a sunspot drawing dates back into the 12th century to John of Worcester in 1128.

Johannes was born in Resterhafe (East Friesland). He was the eldest son of eight children of the pastor and astronomer David Fabricius,[4] who conducted extensive astronomical and meteorological research and was in correspondence with Tycho Brahe,[5Johannes Kepler [6] and Simon Marius.[7] Like his father, Fabricius attended the University of Helmstedt. Besides the usual basic studies at the Faculty of Philosophy, he also worked in medicine. However, he moved to the University of Wittenberg in 1606, where he remained for three years and studied geometry, astronomy, chronology and physics in addition to grammar, dialectics and rhetoric.In addition to astronomy, like his father, he was involved in astrology and was convinced that it provided reliable information. He also believed he had found a method of weather forecasting.

In 1609 Fabricius went to Leiden to study medicine at the university there. In the summer of 1611 he returned to Wittenberg and received the title of Master of Philosophy in September. Fabricius returned from university in the Netherlands with telescopes that he and his father turned on the Sun. The men noted the existence of sunspots, being the first confirmed instance of their observation. Since their eyes were affected, they later used a safer method of observation: Using a pinhole they directed the sunlight into a darkened room and looked at the sun disk on a white piece of paper (the principle of the camera obscura). The existence of the stains could be proven without any doubt. Their daily movement on the sun disk was aptly attributed to a self-rotation of the sun. In June of the same year, Johann Fabricius published a 22-page book De Maculis in sole observatis et apparente earum cum Sole conversione narratio in Wittenberg, in which he describes all the details of the discovery and credits his father with a due share.

Title page of De Maculis in sole observatis et apparente earum cum Sole conversione, Narratio (1611)

Title page of De Maculis in sole observatis et apparente earum cum Sole conversione, Narratio (1611)

Solar activities and their related events in general have probably already been observed by the Babylonians. It is further believed that sunspots were mentioned by the ancient Greek scholar Theophrastus. The first known drawing of sunspots dates back to John of Worcester in 1128. Also Benedictine monk Adelmus probably observed a large sunspot that was visible for eight day, but he concluded to be observing the transit of Mercury. Also Galileo and Christoph Scheiner probably observed sunspots, unaware of Fabricius’ work.[3] In 1613 Galileo refuted Scheiner’s 1612 claim that sunspots were planets inside Mercury’s orbit, showing that sunspots were surface features.

The observations on sunspots continued, but the physical aspects of sunspots were not identified until the 20th century. In 1845, Henry and Alexander observed the Sun with a thermopile and determined that sunspots emitted less radiation than surrounding areas. The emission of higher than average amounts of radiation later were observed from the solar faculae. Sunspots had some importance in the debate over the nature of the Solar System. They showed that the Sun rotated, and their comings and goings showed that the Sun changed, contrary to Aristotle, who had taught that all celestial bodies were perfect, unchanging spheres. This discovery contrasted also the Church’s doctrine that the sun should be “unpolluted”, as the Virgin Mary were.

Almost nothing is known about his future life. Apparently, he initially continued his medical studies. Johannes Fabricius died on a trip to Basel, where he wanted to obtain his medical doctorate.

At yovisto you can learn more about the Sun in the lecture The Inconsistent Sun at Gresham College by Professor Claudio Vita-Finzi.

References and Further Reading:

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