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Student Guide to Activity 1: Features of the Sun - page 2 / 7

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Thus, from Earth, we see spots on the Sun. In some photographs, we can also see light colored areas around groups of sunspots that resemble tufts of cotton candy. We call these fluffy looking fringes plages.

Sunspots are the source of massive releases of energy called solar flares, the most violent events in the solar system. In a matter of minutes to several hours, a solar flare releases about 10,000 times the annual energy consumption of the U.S. Solar flares give off radiation that includes X-rays, ultraviolet rays, and charged particles called protons and electrons. This sudden surge in radiation can damage spacecraft and even give a dose or radiation to travelers flying in airplanes over the polar regions.

Also visible for only min- utes, are granulations in the Sun’s photosphere. Granulations are rising and falling columns of hot gases that look like fluffy marsh- mallows arranged in a honeycomb pattern. The tops of these granules form the Sun’s “surface.” Al- though we refer to the Sun’s “surface” as the photo- sphere, you probably know that the Sun has no solid surface, unlike Earth. It is an uneven sphere of glow- ing, hot gas!

The bright areas in the X-ray image from the Japanese Yohkoh satellite are called “active regions,” which contain hot, dense gas. They are also the source of the most intense X-ray eminations. The dark areas are coronal holes.

Courtesy of the Lockheed Palo Alto Research Laboratory and the National Astronomical Observatory in Japan.

Just as the Sun disappears behind the Moon during a total solar eclipse, a flash of bright red light appears. This colorful layer of the Sun, called the chromosphere, becomes visible for a brief instant. Although we know little about the chromosphere, there are curious, permanent features of the chromosphere, called spicules, that we can study in more detail. There are so many of these fine, bright, hairlike features, that they are always visible near the Sun’s edge, even though an individual spicule lasts only minutes. Like sunspots, spicules rise and fall vertically above the Sun’s surface.

One of the most spectacular features of the Sun are solar prominences. They appear to stream, loop and arch away from the Sun. The most recognizable prominences appear as huge arching columns of gas above the limb (edge) of the Sun. However, when promi- nences are photographed on the surface of the Sun, they appear as long, dark, threadlike objects and are called filaments. Like sunspots, prominences are cooler (about 10,000 ½C) in relation to the much hotter background of the Sun’s outer atmosphere (about 1,500,000 ½C). Prominences can also erupt from the Sun with a tremendous burst of energy.

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Student Guide, Activity 1: Features of the Sun © Space Science Institute, 1999. All Rights Reserved

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