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Solar Eclipses

Alignments of the Sun, Moon and Earth lead to a solar eclipse; what happens during one.

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Solar Eclipses

Can you see a solar eclipse?

Of course! This photo of a partial solar eclipse was taken on May 20, 2012 in Gilbert, Arizona. The maximum was 82% at that location. Further north people experienced totality. The next two eclipses in North America will be a partial on October 23, 2014 and a total on August 21, 2017. If you try to view an eclipse, be sure you use eye protection!

Solar Eclipses

When a new moon passes directly between the Earth and the Sun, it causes a solar eclipse (Figure below). The Moon casts a shadow on the Earth and blocks our view of the Sun. This only happens if all three are lined up and in the same plane. This plane is called the ecliptic. The ecliptic is the plane of Earth’s orbit around the Sun.

The Moon’s shadow has two distinct parts. The umbra is the inner, cone-shaped part of the shadow. It is the part in which all of the light has been blocked. The penumbra is the outer part of Moon’s shadow. It is where the light is only partially blocked.

The moon's position during a solar eclipse

During a solar eclipse, the Moon casts a shadow on the Earth. The shadow is made up of two parts: the darker umbra and the lighter penumbra.

When the Moon's shadow completely blocks the Sun, it is a total solar eclipse (Figure below). If only part of the Sun is out of view, it is a partial solar eclipse. Solar eclipses are rare events. They usually only last a few minutes. That is because the Moon’s shadow only covers a very small area on Earth, and Earth is turning very rapidly.

Solar eclipses are amazing to experience. The light disappears so that it's like night, only strange. Birds may sing as they do at dusk. Stars become visible in the sky. It gets colder outside. Unlike at night, though, the Sun is out. So during a solar eclipse, it's easy to see the Sun's corona and solar prominences. 

Picture of a total solar eclipse

A photo of a total solar eclipse.


  • During a solar eclipse, the new moon passes between Earth and Sun.
  • The umbra is the part of the shadow in which light is completely blocked.
  • The penumbra is the part of the shadow that is partially lit.


  1. What is a solar eclipse?
  2. What causes a solar eclipse?
  3. What is the relationship of the umbra and the penumbra?

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penumbra Outer part of shadow that remains partially lit during an eclipse.
solar eclipse Occurs when the Moon passes directly between the Earth and Sun; the Moon’s shadow blocks the Sun from view.
umbra Inner, cone-shaped part of a shadow when all light is blocked during an eclipse.

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