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Home | Total Solar Eclipse 22nd July 2009 | What exactly happens during such an eclipse?
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| What exactly happens during such an eclipse? |
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If you are lucky enough to be in the path of totality, you will see the Sun slowly covered by the Moon. This partial phase lasts up to an hour or more, depending on where and when you see the eclipse. During most of the partial phase, the dimming of sunlight is hardly noticeable; when seen through proper equipment, the Sun will appear to have a "bite'' taken out of it. Then, as the Moon slides totally in front of the Sun, the magic really begins! The sky will darken. The Moon's black disc will look almost like a hole in the sky, and peeking around the black disc should be a number of pinkish solar prominences, gigantic explosions of hot hydrogen gas that boil off from the Sun in spectacular arching shapes.
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| At the last instant before the Moon completely covers the Sun, observers may behold two fascinating sights. First, the last bit of sunlight streaming past the Moon might seem to break into "beads,'' (known as Bailey's Beads after the English astronomer Francis Bailey, who first described their appearance in 1836). |
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| Bailey's Beads arise from sunlight passing through lunar valleys in the Moon's uneven, cratered surface. The beads will last a few seconds, and wink out as the Moon glides further in front of the Sun. And finally, just as the last bead is visible, light from the Sun's outer atmosphere will start to be visible around the Moon, creating a glowing ring of light. This is called the "Diamond Ring Effect.'' |
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| The most dramatic part of the total eclipse is being able to see the Sun's corona, a ghostly aura streaming away from the Sun in all directions. Total eclipses are the only time most people ever get to see this delicately-hued layer of the Sun's outer atmosphere. Indeed, we on Earth are very lucky to live on the only planet in the solar system with a moon the right size and distance to just cover the Sun's disc, but not cover its corona as well. Our Moon is about 400 times smaller than the Sun, but it is also about 400 times closer, too, so it appears to be the same size in the sky. |
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| The corona is the Sun's outermost atmospheric layer, with extremely hot gas (reaching temperatures near a million degrees) flowing off many millions of miles into space. The corona is usually outshone by the Sun's visible layer, called the photosphere, which is one million times brighter. |
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