This is the one area of astronomy where we don’t encourage you to do your own observing without getting careful instructions or filters from your instructor.) (We emphasize what your parents have surely told you: looking at the Sun for even a brief time can cause permanent eye damage. Occasionally, these spots are large enough to be visible to the unaided eye, and we have records going back over a thousand years from observers who noticed them when haze or mist reduced the Sun’s intensity. They look darker because the spots are typically at a temperature of about 3800 K, whereas the bright regions that surround them are at about 5800 K (Figure 1). The first evidence that the Sun changes came from studies of sunspots, which are large, dark features seen on the surface of the Sun caused by increased magnetic activity. (credit: NASA Goddard Space Flight Center, Alan Friedman) The mottled appearance of the Sun’s surface is granulation. Although sunspots appear dark when seen next to the hotter gases of the photosphere, an average sunspot, cut out of the solar surface and left standing in the night sky, would be about as bright as the full moon. The largest spot shown here is about 11 Earths wide. You can see the dark, central region of each sunspot (called the umbra) surrounded by a less dark region (the penumbra). Sunspots: This image of sunspots, cooler and thus darker regions on the Sun, was taken in July 2012.
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