There are two types of eclipses that can be observed on Earth, a lunar eclipse and a solar eclipse. An eclipse occurs when a moon or planet moves into a shadow created by another moon or planet.  A solar eclipse occurs when the moon, which is orbiting around the Earth, moves between the Earth and the Sun which creates a shadow on Earth and they only last for a few minutes.

Eclipse Schematic

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There are three types of solar eclipses which are an annular solar eclipse, a partial solar eclipse, and a total solar eclipse. A partial solar eclipse occurs when the moon and earth are not lined up exactly making only part of the sun have a dark shadow.  An annular eclipse occurs when the moon is the farthest away from the Earth and the moon appears to be a small dark disk on top of the sun and does not cover the whole sun. The last type of eclipse is a total eclipse. This occurs when the moon and earth are perfectly aligned making only the corona of the sun visible. This kind of eclipse will make the sky dark for a couple minutes.

Types of Solar Eclipses

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The moon casts two different shadows on the Earth during an eclipse called the Umbra and the penumbra. The umbra is the dark center of the moons shadow and gets smaller as it reaches Earth. The penumbra is the second shadow and gets larger as it reaches Earth. To see a total eclipse you must be in the path of the umbra, while those in the penumbra will see a partial eclipse. These shadows only cover a small portion of the Earth, so although an Eclipse occur roughly every 18 months it is a rare occasion to observe a total solar eclipse.

The next visible solar eclipse in the United States is Monday August 21st. Maps of the path for this eclipse can be found on the NASA Eclipse website (  It is not safe to look directly at the sun, for safe ways to view this year’s eclipse please see the Viewing section.



[1] Wild, Flint. “What Is an Eclipse?” NASA, NASA, 1 June 2015,

[2] “Hybrid Solar Eclipse.” Exploratorium, 13 July 2017,

[3] “Why Eclipses Happen.” Exploratorium, 21 July 2017,