JF Ptak Science Books Post 1982 History of Holes series #44
The composition of the sun remained basically hidden to scientists until relatively recently–certainly it was well into the 20th century before astronomers/astrophysicists got a good idea of what the sun is, exactly. The perfection of god's creation and Aristotle's unchanging nature of the sun must've been suspected for a long time given its coronal displays during total eclipse and ancient unaided observation of sunspots (which at least suggested that the sun rotated), but the true nature of the "imperfect" nature of the star wasn't firmly exhibited until the work of Thomas Harriot and the Fabricus and Galileo and Scheiner–but then there wasn't that much that could be employed from the data. So too true even with Bunsen and Kirchhoff in their profound invention and discovery in 1859 of the spectrographic analysis of the sun revealing its chemical composition (finding the absorption lines in the spectrum of the sun contained hydrogen,m nicekl, iron, sodium,cacium, and magnesium as starters)–this information was essential in establishing discoveries that would come much later on. (Interesting to note here that the first record of a solar flare is made in this same year by Richard Carrington, and also that this year saw the publication of On the Origin of Species as well as Riemann's hypothesis and Maxwell's kinetic theory of gases–a big year in the history of science).
The interesting hypothesis of sunspots as "holes" in the surface of the sun was made by Alexander Wilson (professor of astronomy at the University of Glasgow) in his paper "Observations on the Solar Spots" on 1 January 1774 and published in the Philosophical Transactions (volume 64, pp 1-30, and available here). It was one attempt at an explanation for the mysterious black spots that also opened the door to the possibility of the sun being inhabited. The spots then would have been conical holes in the sun's photosphere, with the dark part coming from a glimpse of the interior (and presumably cooler) part of the sun.
From the vantage point here in the future this looked like not such a great idea, especially coming only a few years before the (1787) discovery by William Herschel that the sun and the rest of the solar system was in motion relative to the stars and was slowly moving towards a point in the contellation Hercules, which was an enormous scientific breakthrough as well as philosophical-theological chllenge, a cosmological "aha!" moment. That said, Mr. Herschel also held the view that sun spots were possibly cavities in the surface of the sun, the reasoning for which was very good and at times convincing in the absence of anything better, a pretty good product for its time
The beautiful image introducing this post was designed about a hundred years after the Wilson paper, and appeared in the prolific Amédée Guillemin's (1826-1893) The Sun (translated from the original French in 1875), and which is available in full text pdf from The Haiti Trust. Guillemin spends a chapter on sunspots and holes and presents a convicing history of the idea, and that according to Wilson and others the spots were cavities in a liquid globule envelope and revealed the solid mass of the sun "through a cloudy atmosphere with a grey tiny all around" (page 214).
The epilogue of Guillemin's book addresses the issue of life on the sun ("Is the Sun Inhabited?") and in his review Guillemin very plainly makes the case that it is "absolutely impossible to support life" on the sun due to the heat–presently. He qualifies his assessment finally by asking "Will it become habitable?", and responding that it was "very possible" (page 295), but that it would have to take place in a future where the rest of the planets and everything else has gotten colder.