National Sharing the Sky Foundation
A very special year has begun. As readers around the world celebrate the incoming year, they also are firming up their plans for viewing some extraordinary events in the sky.
The most important thing happening this year, particularly for viewers living in the United States, will be a total eclipse of the Sun. On August 21, the shadow of the Moon will track across the United States from the coast of Oregon in the morning, crossing the country and reaching the vicinity of Kansas City around noon, and then leaving the east coast of South Carolina late in the afternoon. Almost all of North America will experience a partial eclipse of the Sun.
But there is a tremendous, almost indescribable difference between a 99% partial eclipse and a 100% total eclipse. A 99% eclipse is still a partial eclipse, and it takes the extra one percent to turn the partial into a total eclipse. If it is only partial, the sky will begin to darken slightly as the Sun’s appearance changes from whole Sun to a crescent. As the eclipse deepens, the crescent will get progressively thinner until, at the 99% level, all that is left is a thin line of sunlight. If you look toward the west, you will see the dark shadow of the Moon approach you, pass by, then recede as it races to the east. However, the eclipse is still partial, and then the crescent will widen and brightness will return.
That last one percent makes all the difference. This is what you might see: The Sun’s line of light continues to shrink until all that is left is a point of light. From the west, the shadow continues to grow and darken. Looking back at the Sun, you will see what looks like a diamond ring. The diamond is a single bright point of sunlight, and surrounding the darkened Moon the Sun’s corona is starting to appear.
The Sun has vanished, leaving in its place a jeweled crown. The corona begins to appear and stretch out. The corona is the outer atmosphere of the Sun, and its temperature can exceed a million degrees centigrade. But as hot as it is, the corona is far thinner than the rest of the Sun; it is almost a vacuum.
There may also be erupting prominences coming out of the edges of the Sun. They look like small flames, but they are quite a bit larger than the Earth. After a minute or two, the edge of the Moon’s shadow approaches, a second diamond ring appears in an outburst of light, and the total phase of the eclipse is over.
It is my hope that you will make every effort to view this summer’s total eclipse of the Sun. If you live near Vail, Arizona, where Wendee and I live, and do not travel to a place like Madras, Oregon, where we plan to be, you will see about half the Sun obscured by the Moon. In any event, the ethereal beauty of an eclipse will remind you that we live on a delicate world that moves around the Sun, and that on rare occasions, our Moon can block out the Sun’s light and create a total eclipse, one of the truly most amazing things humanity can witness.
