Volume: 04, Issue: 16 04/05/2006 
The Sun's corona, or outer atmosphere, is visible during totality -- when the Sun is totally obscured by the Moon's shadow. Image credit: NASA TV.
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The sun creates a "diamond ring" effect as it emerges after totality. Right: Solar flares, or "prominences" are visible at the edge of the moon's shadow. Image credit: NASA TV.
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The Moon's shadow falls on Earth, as seen from the International Space Station 230 miles above. Image credit: NASA.
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Other Articles in This Issue:
NASA’s Mars Reconnaissance Craft Begins Adjusting Orbit
Cassini Finds “Missing Link” Moonlet Evidence in Saturn’s Rings
Venus within ESA Probe Reach
Professional Development Workshops and Institutes
 

Total Solar Eclipse

On March 29, 2006, the normally sunny African sky darkened as the Moon covered the Sun. A total solar eclipse occurs when our satellite passes between Earth and our star. Although the Moon is 400 times smaller than the Sun, the Sun lies 400 times father from Earth. When this celestial lineup is dead-on the two bodies possess the same angular size (about ½ degrees), and a total solar eclipse occurs.

Before reaching Africa, this total eclipse began over Brazil at sunrise. The eclipse path then crossed the Atlantic Ocean, reaching landfall again on the African coast. More than 1.5 million people in Ghana’s capital, Accra, experienced totality for nearly three minutes. Maximum eclipse occurred over the Chad-Libya border, where observers experienced four minutes and seven seconds of totality. This year's eclipse is also special because the total phase lasts over four minutes at the center of the path. This is quite long for a total solar eclipse since most last just a minute or two.

The eclipse path then crossed Egypt and the Mediterranean Sea, and entered Turkey. The eclipse ended at sunset over northern Mongolia. The path of totality spans only 114 miles, but observers over a much wider area of northern Africa, Europe, and central Asia saw a partial solar eclipse.

Watching an eclipse is a spectacular sight – an initial dark bite grows and swallows the Sun’s yellow globe. In a total eclipse, all that is left is the Sun’s glowing outer atmosphere called the corona. In the minutes before totality, the landscape gains a golden hue, shadows become sharper, and the temperature falls. Silvers of sunlight shine through valleys on the Moon’s edge and create what are called Baily’s beads. The beads gradually disappear until a solitary spot remains – an effect called the diamond ring. Darkness ensues, and then the process repeats, in reverse.

Total solar eclipses are of special interest to astronomers because eclipses are the only time they can study the corona. Scientists still do not understand why the corona is so hot. Its temperature is 1 to 2 million degrees Fahrenheit while the Sun's bright surface is only 10,000° Fahrenheit. Careful measurements and experiments are made during a total eclipse help to unravel this mystery.

Use extreme caution when viewing the Sun. At no point during any eclipse is it safe to look directly at the Sun without a proper filter. Use an approved coated-glass or optical Mylar solar filter or a #14 welder's glass.

The next total solar eclipse occurs August 1, 2008. It follows a path over northern Canada, Greenland, Siberia, Mongolia, and China. It will last about 2 minutes. The next total eclipse visible from the United States will not happen until August 21, 2017.

To read more about the March 29, 2006, total solar eclipse, please visit the following websites:
http://www.astronomy.com/asy/default.aspx?c=a&id=4059
http://www.nasa.gov/vision/universe/solarsystem/sun_earthday2006.html.

    
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