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How does a solar eclipse occur?

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near and far sides of Earth's Moon — Moon (Left) Near side of Earth's Moon, photographed by the Galileo spacecraft on its way to Jupiter. (Right) Far side of the Moon with some of the near side visible (upper right), photographed by the Apollo 16 spacecraft.

A solar eclipse occurs when the Moon passes directly between Earth and the Sun, casting a shadow on Earth’s surface and obstructing some or all of the Sun’s light.12

This phenomenon happens only during a new moon when the Moon is near one of the nodes of its orbit, where its path intersects the ecliptic. The resulting shadow consists of two primary regions:3
* Umbra: A central, narrow cone where the Sun is completely obscured, resulting in a total solar eclipse for observers within this path.12
* Penumbra: A wider surrounding area where the Sun is only partially covered, resulting in a partial solar eclipse.23

If the Moon is at its farthest point from Earth during the eclipse, its apparent size may be too small to cover the Sun completely, leaving a visible rim of light known as an annular solar eclipse. Because the Moon’s shadow is narrow, solar eclipses are visible only from limited regions on Earth.123