Billy Sharpe, Age 13, Of Nashville, Tenn., for his question:

How do sunspots form?

Sunspots have been observed since the time of Galileo. During the igy, they were Under constant watch for 12 months. This sunspot surveillance resulted in an amazing discovery which can rightly be called a flip flop. But the igy scientists came no Nearer to discovering what causes these dark rashes to mar the brilliant face of the Sun.

A sunspot rarely if ever starts as a single blemish. It is seen first as a pair Of small spots somewhere between 5 and 30 degrees north or south of the sun's equator. The baby blemishes are dark blots surrounded by paler fringe areas. At first they are separated by perhaps 50,000 miles. The sunspot rash develops fast and reaches its peak in about a week. It subsides more slowly, and the blemish may last for several weeks.  The two small spots grow larger and pull apart. They move westward with the sun's rotation, and the forward or preceding spot becomes larger.

At its peak, a large sunspot group may cover an area of 5 billion square miles. If it is near the equator, it circles around the rotating sun in about 26 days. The sun's rotation is slower farther from the equator and sunspots at latitude 40 degrees make the round trip in 2  Days. The following spot begins to shrink and break apart after about a week. Soon its Fragments disappear, and the preceding spot goes on alone, perhaps for several weeks. Finally it shrinks and disappears. The dark umbra at the center of a sunspot looks like a hole in the bright face of The sun. It is the center of a magnetic storm, and its temperature is around 4000 Centigrade degrees.

This is merely 2000 degrees cooler than the seething surface of the sun, and a sunspot looks dark only by comparison with the surrounding brilliance. Sunspots reach peak activity every 11 years or so, At which time the sun is marred with rashes almost every day. At the low point of the sunspot cycle, there may be no rashes for several days. During the igy, sunspots revealed an amazing fact about the magnetic nature of the sun. At the peak of a sunspot cyc1e, the sun's magnetic poles do a flip flop. The north and south magnetic poles change places. A sunspot pair is bipolar, with one spot having a south and the other a north Magnetic pole. In the northern hemisphere, if the preceding spot is south polarity, The following spot will be north polarity. South of the equator, the preceding spot Will be north and the following spot south polarity. This order holds throughout a Sunspot cycle. In the next cycle, the order of polarities is reversed in both Hemispheres.