ROYAL ASTRONOMICAL SOCIETY / SCIENCE PHOTO LIBRARY ROYAL ASTRONOMICAL SOCIETY / SCIENCE PHOTO LIBRARY
Sunspot observations, made on 5th June 1864 by the Scottish amateur astronomer James Nasmyth (1808-1890). A scale is at bottom. This close-up shows the cooler central areas (dark) and the hotter (lighter) areas round each sunspot. Sunspots, first observed with telescopes in 1610, are areas of magnetic activity that are cooler than the rest of the Sun's surface. They are massive structures, ranging in size from hundreds to thousands of kilometres across. This drawing was published in 1885 in Nasmyth's autobiography.
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