In the beginning, the discovery was not accepted, and many felt that these were not spots but bodies which, coming between the Earth and the Sun, projected their shadow on the star. But then the frequency and accuracy of telescopic observations improved and sunspots were even used to prove that the Sun revolves around its own axis every 27 days, and not like a rigid sphere, since it moves faster at the equator than at the poles. However, one question still remained: what are sunspots? For a long time it was believed that they were clouds which moved over the surface of the star. Then in 1801, the German astronomer Wilhelm Herschel, who discovered Uranus, theorized that the spots were not clouds but "holes" in the clouds: according to Herschel, the Sun was covered by an incandescent layer, the photosphere, which surrounded a darker and colder portion which could only be seen when the incandescent clouds would tear apart. "This region", wrote the astronomer "is very probably inhabited, as is the rest of the planets, by beings whose organs have adapted to the very unusual environment of that immense sphere". Many other theories were developed during that time period in which the sunspots were thought to be hurricanes, bubbles floating in a liquid Sun, impacts by meteorites, summits of mountains which broke through fiery clouds and even gigantic solid rafts wandering over a molten surface. Now, 150 years later, many of the Sun's mysteries have been solved. Except for the inhabitants, Herschel's explanation for sunspots was surprisingly close to the truth: sunspots are in fact colder regions of the photosphere, the visible surface of the star, with a temperature of a "mere" 4 500 degrees Celsius compared to the 6 000 degrees in the surrounding areas. Distributed over approximately two strips symmetric to the solar equator, they vary in size and quantity according to 11-year cycles, shifting from the poles to the equator, where their intensity increases. However, there are other questions which still have not been answered: how is matter distributed inside the star? What influence does the Sun's activity have on the Earth's climate? How constant is the flow of solar radiation?
In the beginning, the discovery was not accepted, and many felt that these were not spots but bodies which, coming between the Earth and the Sun, projected their shadow on the star. But then the frequency and accuracy of telescopic observations improved and sunspots were even used to prove that the Sun revolves around its own axis every 27 days, and not like a rigid sphere, since it moves faster at the equator than at the poles. However, one question still remained: what are sunspots? For a long time it was believed that they were clouds which moved over the surface of the star. Then in 1801, the German astronomer Wilhelm Herschel, who discovered Uranus, theorized that the spots were not clouds but "holes" in the clouds: according to Herschel, the Sun was covered by an incandescent layer, the photosphere, which surrounded a darker and colder portion which could only be seen when the incandescent clouds would tear apart. "This region", wrote the astronomer "is very probably inhabited, as is the rest of the planets, by beings whose organs have adapted to the very unusual environment of that immense sphere". Many other theories were developed during that time period in which the sunspots were thought to be hurricanes, bubbles floating in a liquid Sun, impacts by meteorites, summits of mountains which broke through fiery clouds and even gigantic solid rafts wandering over a molten surface. Now, 150 years later, many of the Sun's mysteries have been solved. Except for the inhabitants, Herschel's explanation for sunspots was surprisingly close to the truth: sunspots are in fact colder regions of the photosphere, the visible surface of the star, with a temperature of a "mere" 4 500 degrees Celsius compared to the 6 000 degrees in the surrounding areas. Distributed over approximately two strips symmetric to the solar equator, they vary in size and quantity according to 11-year cycles, shifting from the poles to the equator, where their intensity increases. However, there are other questions which still have not been answered: how is matter distributed inside the star? What influence does the Sun's activity have on the Earth's climate? How constant is the flow of solar radiation?
