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Description of a Solar Eclipse

When eerie twilight fell upon the ancient earth in the middle of the day, servants and kings alike trembled. As the sun turned black, the Chinese streets burst into noise as the nation tried to scare away the dragon eating the sun. Thousands of years later, in 585 BC, Lydia and Mede ceased a five-year war and bargained for peace after witnessing a dark sun. Today, scientists realize that neither dragons nor the end of the world are near when an eclipse occurs, but rather that the moon's shadow is falling upon the earth. Because of the shape and position of the lunar orbit, the moon casts three types of shadows, which produce four categories of solar eclipses.

Partial Eclipse
- A partial eclipse takes place when the moon blocks only a portion of the sun. When this happens, the sun looks like a crescent, much like the early phases of the moon. Only the moon's penumbra, or outer shadow, which blocks the sun's angular rays, crosses the earth during this event. Its umbra, or inner shadow, which blocks direct rays, misses the earth. This partial shadow occurs because the moon's orbit is slightly out of alignment with the Earth's. This is the most common type of solar eclipse.
Annular Eclipse
- Annular eclipses occur when the sun, moon and earth are exactly aligned, but while the moon is too close to the sun to cover it completely. During this type of eclipse, the edges of the sun shine around the smaller moon. The moon's elliptical orbit is responsible for this event. Because its path is elongated, its distance from the earth varies, creating a difference in the apparent sizes of the sun and moon. When the moon is farthest from the earth, not only does it appear smaller than the sun, but its umbral shadow is also too short to reach the planet. The shadow beneath it, the antumbral shadow, falls across the planet instead.
Total Eclipse
- When the sun, moon and earth are exactly aligned and the moon is also close to the earth, a total eclipse occurs. During this type of eclipse, the umbral shadow moves across the globe in a long, narrow path, called the Path of Totality. Outside this zone, the moon's penumbral shadow also crosses the earth, dimming the sky, but not darkening it in the same way as the umbra. When the moon completely covers the sun, the solar corona, a crown of blazing plasma, appears around its edges. Total eclipses account for roughly 27 percent of all solar eclipses.
Hybrid Eclipse
- Occasionally, a total eclipse will turn into an annular eclipse as the moon's shadow moves across the earth. Although two to five eclipses occur every year, less than five percent are hybrids. Scientists predict that the next one will occur in 2013. Like all solar eclipses, it can occur only on the day of the new moon, when the three celestial bodies are aligned.

Astronomy