Sunspot imaged with different exposures. At left is an exposure of 1/500 seconds. At right is an exposure of 1/150 seconds. The different exposures show different aspects of the sunspot's structure. Sunspots are areas of magnetic activity that are cooler than the rest of the Sun's surface. They range in size from hundreds to thousands of kilometres across. The darkest regions (nearly vertical magnetic fields) are the umbras, surrounded by penumbras (bronze regions). The yellow background consists of convection cells called solar granules. This sunspot is around 22,000 kilometres across. Images obtained on 9 September 1990 with the McMath-Pierce Solar Telescope.