Of Galileo and Modern Sunspots

Discoveries & Opinions of Galileo

    Although it was undeniable that scientific studies of sunspots had been carried out with the telescope, there was a controversy as to who was the ‘pioneer’ in the discovery of sunspots. There is a consensus, however, that Galileo Galilei and Thomas Harriot were the first, around 1610; that Johannes and David Fabricius and Christopher Scheiner first observed them in March 1611. However, Johannes Fabricius was the first to publish a book on them. His book, De Maculis in Sole Observatis (On the Spots Observed in the Sun) appeared in 1611, but it remained unknown to the other observers for some time. A summary from the chapter "Letters on Sunspots" in the book Discoveries and Opinions of Galileo (Galilei, Galileo [1564-1642], 1957) gives an interesting account of what might had happened at that time between the great astronomers in resoving the issue of who discovered sunspots first:

Summary of "Letters on Sunspots":

Father Christopher Scheiner, a Jesuit professor at the University of Ingolstadt, sent his observations and theories about sunspots in letters to Mark Welser, a wealthy merchant. He published them and sent them to Galileo, and Scheiner’s name was concealed under the pseudonym Apelles latens post tabulam. The priority in the discovery of sunspots later caused great bitterness between Scheiner and Galileo, and a great deal of it has to do with the trouble with the church later. But the irony of this dispute was, none of the two men were the first to have observed sunspots and published their findings first. The first observation of sunspots was mentioned in the time of Charlemagne. The first person to publish the sunspot findings was Johann Fabricius of Wittenberg, whose booklet was printed in the summer of 1611. Galileo was also charged with having learnt of sunspots from Scheiner’s letters, but it was later disproved.

    At Galileo’s time, it was believed that the heavens are pure, and hence if it was known that blemishes could appear and disappear on the face of the sun itself, the incorruptibility and inalterability of the heavenly bodies was destroyed. Hence, Scheiner accounted for the sunspots by assuming a number of small planets revolve about (or beneath) the sun, and hence obstruct our vision to create sunspots.

    He even proposed that they could be stars. However, Galileo was bold enough to place the location of the spots right on the surface of the sun, or at least no farther from it than clouds are from the earth. His evidence of his theory was undisputed for it was mathematical. However, as to the nature of the spots, he remained uncommitted, though he did not hesitate to reason about this matter by analogy with terrestrial phenomena, a very radical departure at the time.

    His avowed enemies in the church never understood him at all; to them, Galileo was attacking the church. However, for him, he was protecting it from the commission of a fatal error.

from "Discoveries and Opinions of Galileo (1st Publication)" [Page 80 - 145]

    In any case, Galileo, although seen as one of the greatest mathematicians and astronomers today, was not viewed so positively in those days. His radical ideas and foundings brought him much trouble with especially the Catholic Church, by challenging the norms of the heavens as believed in those times. Ultimately, he spent the last eight years of his life under house arrest.


Scientific progress on Sunspots in the Past and the Present

    The turning point in the discovery of sunspots came about with the invention of the telescope by the Dutch in about 1608. With this equipment, many things in space, the sun, the moon, the stars, the planets, could then be seen and observed, thus increasing studies and discoveries in the field of astronomy. According to David Dearborn, an archaeastronomer and stellar physicist, "In Europe, where the telescope was first invented and used, it informed them that sunspots existed. There was a belief that the heavens were perfect, and frequently people see only what they expect to see. So when they first saw sunspots, they were amazed. They didn’t really know what sunspots were, because they didn’t have the tools to measure the magnetic fields that were producing these things, and they definitely sparked curiosity."

    In the meantime after the debate with Galileo, Scheiner continued in his extensive research on sunspots. He abandoned the idea that the sun was perfect, and officially acknowledged the existence of sunspots. He published his results in Rosa Ursina (The Rose of Orsini), which "became the standard treatise on sunspots for over a century". After this ‘definitive’ study by Scheiner, many interested astronomers undertook sunspots research, and in the years 1610-1645, many credible sunspots records were undertaken, among some by Pierre Gassendi, Bologna Giovanni, and Battista Riccioli.

    With the rise of astrophysics, modern studies of sunspots were carried out. George Ellery Hale (1868-1938) was one of the early investigators of sunspots phenomena. It is hence, with its rich history and the advanced technology of today, which makes sunspots a phenomenon recognized by astronomers all over in the present times.

Resources: "Discoveries and Opinions of Galileo (1st Publication)" [Page 80 - 145]   
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