3.10: Solar Eclipses

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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. Much of the United States experienced a total solar eclipse on January 31, 2017. The next total solar eclipse in North America is April 8, 2024 and will be visible in the US from Texas to Maine. If you try to view an eclipse, be sure to 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.

Summary

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.

Review

What is a solar eclipse?
What causes a solar eclipse?
What is the relationship of the umbra and the penumbra?

Explore More

Use this resource to answer the questions that follow.

What happens during a solar eclipse? What happens during a total solar eclipse?
What can scientists learn during total solar eclipses that they can’t otherwise learn?
How do we know that the corona is hotter than the Sun’s surface?
How did a total eclipse prove Einstein’s general theory of relativity?
What do you need to do to see a total eclipse? How long does it last?
What safety precautions do you need to follow before you view an eclipse?
When is the next total solar eclipse in North America?