Andy Johnston, age 13, of Logan, West Virginia for his question:
How do sunspots form?
Before we even think about this topic, let’s consider a word of warning. Human eyes are not strong enough to take a direct look at the glorious face of the sun. Its dazzling radiation damages the delicate retinas. People have been blinded permanently by staring directly at the sun, even on cloudy days or during eclipses. Let’s not even try to rig up home made contraptions to view the sun. They may or may not be safe. But the risk is too great to take a chance.
Several famous observatories keep the sun’s complexion under daily observation and hour by hour records of the sunspots as they come and go. During the eleven year sunspot cycle, the number of these dusky solar rashes increase and decrease. Through each cycle, they may increase from five to 500 and then decline.
When first observed, a new sunspot is a rash of darkish specks on the sun’s dazzling face. Since the sun rotates toward the east, it comes into view on the western side of the disk, somewhere between solar latitudes five and 40 degrees, north or south of the sun’s equator. Daily it progressed toward the east, taking about two weeks to cross the sun from side to side.
Meantime the specks congeal to form two spots. Both have a darker umbra, perhaps as wide as the earth, surrounded by a paler penumbra, which may be from 10,000 to 100,000 miles in diameter. One spot leads, the other follows as the rotating sun appears to carry them toward the west. The rash may last for several weeks. After disappearing around one side of the sun, they reappear on the opposite side after about two weeks.
Enormous solar flares erupt during the peak of the major sunspot, emitting particles that interfere with communications on the earth. Finally the following sunspot breaks apart and disintegrates. The leader may survive as a single sunspot for another week or so.
The sun’s average surface temperature is around 11,000 Fahrenheit degrees. Sunspots are about 2,000 degrees cooler—and appear darker by contrast. We know that they are in some way related to solar magnetic forces because each spot has a positive or negative magnetic polarity. And for some mysterious reason, this varies with sunspot cycles.
When the leading spot of a pair has a positive polarity, the follow¬ing spot is negative. Throughout one sunspot cycle, all the leaders in the northern hemisphere will be positive and the followers negative. Meantime, in the opposite hemisphere, all the leaders will be negative and the followers positive. This reverses during the next cycle. Then all the leaders north of the equator will be negative and all the leaders in the southern hemisphere will be positive.
A new cycle begins with a couple of minor rashes, perhaps, along latitudes 40 degrees south and north. As the numbers increase, the spots form closer to the equator. At sunspot peak, major rashes form along latitudes five degrees north and south, but never directly on the sun’s equator.