Sometimes when the Moon orbits the Earth, the Moon moves between the Sun and Earth. When this happens, the Moon blocks the light of the Sun from reaching Earth. This causes an eclipse of the Sun, or a solar eclipse. During a solar eclipse, the Moon casts a shadow onto Earth.
There are three main types of solar eclipses:
Total solar eclipse:
- A total solar eclipse is visible from a small area on Earth.
- The people who see the total eclipse are in the center of the Moon’s shadow when it hits Earth.
- The sky becomes very dark, as if it were night.
- For a total eclipse to occur, the Sun, Moon and Earth must be in a direct line.
- No sunlight penetrates the umbra, the inner part of the shadow.
- To observers on the Earth within the umbra, the disk of the Sun will appear completely covered by that of the Moon.
- Such a solar eclipse is said to be total. Because the umbra is narrow at its intersection with the Earth, a total eclipse can be observed only within a very narrow area–the zone of totality.
- Furthermore, because of the relative motion of the bodies, the conical shadow moves rapidly over the terrestrial surface; the totality of the solar eclipse thus lasts only a short time (less than eight minutes at any one place on the Earth).
Partial solar eclipse:
This happens when the Sun, Moon and Earth are not exactly aligned. The Sun appears to have a dark shadow on a small part of its surface.
Annular (an-yə-lər) solar eclipse:
- An annular eclipse happens when the Moon is farthest from Earth.
- Because the Moon is farther away, it seems smaller.
- It does not block the entire view of the Sun.
- The Moon in front of the Sun looks like a dark disk on top of a larger Sun-colored disk.
This creates what looks like a ring around the Moon.
During a solar eclipse, the Moon casts two shadows on Earth.
- The umbra (əm-brə): This shadow gets smaller as it reaches Earth. It is the dark center of the Moon’s shadow. People standing in the umbra will see a total eclipse.
- The penumbra (pə-ˈnəm-brə): The penumbra gets larger as it reaches Earth. People standing in the penumbra will see a partial eclipse.
Solar eclipses happen every 18 months somewhere on Earth. Unlike lunar eclipses, solar eclipses last only a few minutes.
