Flares and auroras are most common during the peak of the sun's 11-year magnetic cycle. 4 and 5. In the corona, or outer atmosphere, which is usually invisible and extends millions of miles into space, the atoms become so active that the temperature jumps again to about a million degrees. The center of the earth is estimated to be about the same temperature as the solar surface, while a lightning bolt the width of your thumb is five times hotter. Scientists figured this out by looking at the color lines in the solar spectrum.
Sunspots are darker and cooler than the rest of the solar surface.
Scientists were surprised, however, to find out that the sun gives off the most light when there are the most sunspots. The equator of the sun rotates once in about 27 days, but the poles take some 9 days longer for each rotation. This is possible because the sun is gaseous, not solid like the earth. Scientists estimate that our sun is about five billion years old and has a life span of another ten billion years or so.