The two main categories of eclipses are solar eclipses and lunar eclipses; each has several subcategories. Eclipses occur often, but are commonly visible in only one part of the world, or aren't visible at all. There are seven types of eclipses, including solar and lunar eclipses, and all eclipses will fall into one of the seven categories.
Total Solar Eclipse
A total solar eclipse happens when the the moon moves between the Earth and the sun in such a way that the sun is hidden from view from the Earth. This generally occurs when the moon is at the point on its orbit that it is closest to Earth, and when the Earth is at a point on its orbit that it is the farthest from the sun. During a total solar eclipse, the sun's body is blocked from view, but the aurora of the sun is visible, creating a circle, or halo, of light.
Partial Solar Eclipse
A partial solar eclipse occurs when the moon passes between the Earth and the sun, much like a total solar eclipse. The difference between a total solar eclipse and a partial solar eclipse is that the moon, during a partial solar eclipse, only blocks a portion of the sun from view from the Earth, rather than blocking the entire sun from view. Partial solar eclipses are more common than total solar eclipses.
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Annular Solar Eclipse
During an annular solar eclipse, the moon moves between the Earth and the sun, as it does in other types of solar eclipses, but the moon's orbit is not at its closest proximity to the Earth. During an annular solar eclipse, the Earth, moon, and sun's orbits are lined up, resulting in the moon appearing directly in front of the sun, leaving the outer rim of the sun, and not just the halo, visible.
Hybrid Solar Eclipse
Due to the curvature of the Earth, a hybrid solar eclipse occasionally occurs. During a hybrid solar eclipse, the eclipse appears as annular over part of its path and total over other parts. Hybrid eclipses are extremely rare.
Total Lunar Eclipse
The Earth's shadow is composed of the umbral shadow, or inner shadow, where all of the sun's light is blocked from reaching the moon, and the penumbral shadow, or outer shadow, where just part of the sun's light is blocked from reaching the moon. A total lunar eclipse occurs when the entirety of moon passes through the Earth's umbral shadow and all of the sun's light is prevented from reaching the moon. During a total lunar eclipse, the moon appears to be an extraordinary color of red or orange.
Partial Lunar Eclipse
A partial lunar eclipse occurs when just a portion of the moon passes through the Earth's umbral shadow; some, but not all, of the sun's light is prevented from reaching the moon. The shape of the moon appears partially shadowed, but the moon retains its usual color. Partial lunar eclipses, unlike many other types of eclipses, are generally visible across an entire hemisphere of the planet, rather than only in specific locations.
Penumbral Lunar Eclipse
During a penumbral lunar eclipse, the moon passes through the Earth's penumbral shadow, rather than the Earth's umbral shadow. Light from the sun is prevented from directly reaching the moon, but light from the sun that is reflected by the Earth does reach the moon, resulting in a faint shadowing effect across the visible surface of the moon. Penumbral eclipses are subtle and can easily be missed by the casual observer.
Eclipses on Other Planets
Eclipses do not happen only on Earth; any planet that has at least one moon can experience an eclipse. Jupiter, Saturn, Uranus, and Neptune all have moons and can experience eclipses. Mars also has moons and can experience eclipses, but due to the size of its moons, Mars can never experience a total eclipse. The frequency, length, and type of eclipse depends on the size of a planet's moon or moons, the distance of the moon or moons from the planet, and the planet's orbit around the sun.