Astronomy
sunspots

What Sunspots are



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sunspots
Rex Trulove's image for:
"What Sunspots are"
Caption: sunspots
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Image by: NASA/Goddard Space Flight Center
© public domain http://svs.gsfc.nasa.gov/vis/a000000/a003800/a003898/

Sunspots have been observed and recorded for over 2,000 years. However, for most of that time, accepted science opinion didn't admit to the existence of sunspots. Only relatively recently have we begun to understand what they are, what causes them, and what various phenomenon are related to them.

Most of our knowledge about them has only occurred since the advent of satellites capable of studying the sun at x-ray wavelengths. (Our atmosphere blocks X-rays.)

To best understand sunspots, it is helpful to understand a little about the sun.

The sun is a large ball of mostly hydrogen gas, which is at present being converted into helium by nuclear processes in the core. Basically, four hydrogen atoms are combined to produce two helium atoms, though the process is substantially more complex than this. The mass of four hydrogen atoms is a little more than the mass of two helium atoms, and the excess is emitted as photon radiation.

Photons take tens of thousands of years to reach the surface of the sun, in part because of the enormous size of the solar sphere and in part because the path isn't a direct one.

At the surface where the photons are radiated out into space as light and other radiation, temperatures are extreme due to the intense radiation. The process of transferring heat from the interior of the sun to the surface of the sun produces huge convection currents which appear rather similar to the top of rapidly boiling pudding.

Like the earth, the sun rotates. However, because of the energy and great gravitational pressure of the sun, as it spins, it produces a gravitational field many thousands of times greater than the field produced by the earth. Since the sun is made up of gases and plasma, it also rotates faster at the equator than at the poles. This causes the magnetic lines of force to twist and intertwine.

The twisted lines of force have the affect of dampening the convection currents at the surface of the sun. This results in areas on the sun's surface that are thousands of degrees cooler than the unaffected areas. Because of the difference in temperatures, the cooler areas appear darker in comparison to the hotter areas. We recognize them as sunspots.

The appearance of sunspots follows a cycle of approximately 11.4 years, from the time of low sunspot activity to times of high sunspot activity, and occasionally the cycle seems to pause for variable periods of time. A new sunspot cycle began early in 2008.

There are some good reasons why this is important, and many of those reasons are still being discovered. For one thing, solar flares, which are ejections of solar material into space, usually come from the regions at the edge of sunspots. Solar flares that happen to be aimed toward the earth can have severe effects on our planet.

For instance, since the particles that shoot past the earth are highly energetic, they can and do disrupt worldwide communications, they can cause satellites to fail completely, they can be deadly to any astronauts that happen to be in space at the time, and can even overwhelm electrical power. Such a happening occurred in the 1970's, resulting in a loss of power over a large portion of eastern Canada and northeastern US.

The energetic particles that were emitted are also responsible for auroras, and the stronger the flare, usually the further south (or north, in the southern hemisphere) the auroras can be seen.

There is growing evidence that our global climate is tied into sunspot activity as well. As yet, we aren't sure what the mechanism is. However during times of unusually low sunspot activity, the globe has experienced unusually cool weather. An example was a period called the 'Little Ice Age' when, for decades; global temperatures were far below normal.

Likewise, times of unusually high sunspot activity correspond to times when global temperatures have been much hotter than anyone now living has ever experienced.

At first glance, sunspots may seem to be a minor thing in the scheme of things. Yet the more we learn about them, the more we realize that they are connected intimately with the climate of our planet, and with the workings of man. They are worth studying in much more detail, and no doubt they will be in the coming decades.

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More about this author: Rex Trulove

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