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Lunar and Solar Eclipses

An eclipse is the result of the total or partial masking of a celestial body by another along an observer's line of sight. Solar eclipses result from the Moon blocking the Sun relative to the Earth; thus Earth, Moon and Sun all lie on a line. Lunar eclipses work the same way in a different order: Moon, Earth and Sun all on a line. In this case the Earth's shadow hides the Moon from view.

When are 2021's solar and lunar eclipses?

Date Type View from U.S.
May 26 Lunar: Total Most of the country
June 10 Solar: Annual East, part of Midwest
November 19 Lunar: Partial Entire country
December 4 Solar: Total None

Total lunar eclipse
The Moon is completely covered by Earth’s dark inner shadow, turning the lunar surface dark.

Partial lunar eclipse
Earth’s shadow covers only part of the lunar disk, so it looks as though something has taken a bite out of it.

Total solar eclipse
The Moon passes between Earth and Sun, completely covering the Sun’s disk.

Annular solar eclipse
The Moon is a bit farther from Earth than average, so a ring of sunlight encircles the Moon as it passes between Earth and Sun.

What is the difference between a lunar and a solar eclipse?

This illustration shows the Moon passing through Earth's shadow during a typical lunar eclipse. The Moon is slightly tinted when it passes through the light outer portion of the shadow, the penumbra, but turns dark red as it passes through the central portion of the shadow, called the umbra.This illustration shows the Moon passing through Earth's shadow during a typical lunar eclipse. The Moon is slightly tinted when it passes through the light outer portion of the shadow, the penumbra, but turns dark red as it passes through the central portion of the shadow, called the umbra. [Tim Jones] From our perspective on Earth, two types of eclipses occur: lunar, the blocking of the Moon by Earth's shadow, and solar, the obstruction of the Sun by the Moon.

When the Moon passes between Sun and Earth, the lunar shadow is seen as a solar eclipse on Earth. When Earth passes directly between Sun and Moon, its shadow creates a lunar eclipse.

Lunar eclipses can only happen when the Moon is opposite the Sun in the sky, a monthly occurrence we know as a full Moon. But lunar eclipses do not occur every month because the Moon's orbit is tilted five degrees from Earth's orbit around the Sun. Without the tilt, lunar eclipses would occur every month.

Lunar and solar eclipses occur with about equal frequency. Lunar eclipses are more widely visible because Earth casts a much larger shadow on the Moon during a lunar eclipse than the Moon casts on Earth during a solar eclipse. As a result, you are more likely to see a lunar eclipse than a solar eclipse.

The Moon casts its shadow on Earth's surface during a total solar eclipse.The Moon casts its shadow on Earth's surface during a total solar eclipse. [Tim Jones]

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Eclipses, Occultations and Transits