Gary Wersimage, age 11, of Toronto, Ont., Canada, for his question:
Do we know what causes sunspots?
As a rule, the radiant complexion of the sun is marred with rashes and dark blotches. These sunspots seem to come and go in cycles. It takes about 11 years for a maximum outbreak to fade to minimum and build up again. Latest observations indicate that two of these 11 year periods are required to complete all the changes in a sunspot cycle.
Astronomers keep the face of the sun under daily observation, and constant records are made of the sunspots that come and go. But we do not know enough at present to explain exactly what causes them to come and go. Several expert astrophysicists have suggested theories to explain them, but none of these theories has been proved.
Most experts agree that these tremendous blotches on the sun are related in some way to its magnetic field. In 1878 the sun's corona was observed during an eclipse, and this streaming halo seemed to act as though it were influenced by magnetic lines of force. Since then it has been established that the sun is indeed surrounded by a magnetic field, and many attempts have been made to measure its force.
The telescope reveals sunspots to be whirlpools of seething gases. For a time most experts regarded them as magnetic storms and solar cyclones, but recent studies indicate that sunspots may be far from stormy. They may be areas of comparative calm in the midst of the gaseous upheaval that is normal on the seething surface of the sun. In the past five years they have been referred to as magnetic islands.
No one knows whether sunspots originate from the surface, from deeper layers below or from the very core of the sun. One theory suggests that they form at the two ends of a U shaped whirlpool that occurs at or near the surface. Another theory suggests that they are formed by a vast vortex of whirling gases at far deeper levels. Sunspots may occur at points where this doughnut shaped whirlpool breaks through the surface. Some astrophysicists suspect that a strong magnetic field exists at the fiery heart of the sun. They suggest that sunspots may spring from this deep region and bring some of this magnetic force to the surface.
No one now can prove what causes sunspots, but we do know that the blotches are highly magnetic. Most, but not all, experts think they are caused by unrest in the sun's magnetic field. But some suspect that their magnetic nature may be a result and not a cause. However, these observers cannot prove what causes the huge areas of solar gases to start their whirling.