Types of Eclipses
The moon's shadow has two parts: a central region (umbra) and an outer region (penumbra). Depending upon which part of the shadow passes over you, you will see one of three types of solar eclipses:
- Total - The entire central portion of the sun is blocked out.
- Partial - Only part of the sun's surface is blocked out.
- Annular - Only a small, ring-like sliver of light is seen from the sun's disc.
If the umbra passes over you, the entire central portion of the sun will be blocked out. You will see a total solar eclipse, and the sky will darken as if it were night time. During a total solar eclipse, you can see the sun's outer atmosphere, called the corona. In fact, this is the only time that you can see the corona, which is why astronomers get so excited when a total eclipse is about to occur. Many astronomers travel the world chasing eclipses.
Photo courtesy NASA
Total solar eclipse
If the penumbra passes over you, only part of the sun's surface will be blocked out. You will see a partial solar eclipse, and the sky may dim slightly depending on how much of the sun's disc is covered.
In some cases, the moon is far enough away in its orbit that the umbra never reaches the Earth at all. In this case, there is no region of totality, and what you see is an annular solar eclipse. In an annular eclipse, only a small, ring-like sliver of light is seen from the sun's disc ("annular" means "of a ring").