Eclipse

:This article discusses astronomical eclipses. For other meanings, see Eclipse (disambiguation).

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An eclipse (Greek verb: ecleipo = 'cease to exist') is an astronomical event that occurs when one celestial object moves into the shadow of another. The term is most often used to describe either a solar eclipse, when the Moon's shadow crosses Earth's surface, or a lunar eclipse, when the Moon moves into the shadow of Earth. However, the term eclipse is also used to describe the phenomenon in which one of the moons of another planet, such as Jupiter or Saturn, passes into the shadow cast by the planet, or (very rarely) when one of Jupiter or Saturn's moons passes into the shadow cast by one of its other moons.

Related Topics:
Greek - Solar eclipse - Lunar eclipse

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An eclipse is a type of syzygy, as are transits and occultations.

Related Topics:
Syzygy - Transits - Occultations

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The most dramatic eclipses from Earth are:

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• Lunar eclipses - the Earth obscures the Sun, from the Moon's point of view. The Moon moves through the shadow cast by the Earth. This can only happen at full moon.
• Solar eclipses - the Moon occults the Sun, from the Earth's point of view. The Moon casts a shadow that touches the surface of the Earth. This can only happen at new moon.

Total eclipses occur where the light source is totally blocked off by the eclipsing body. For total solar eclipses, the viewer is in the umbra part of the Moon's shadow.

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Partial eclipses occur at places where only part of the luminary is covered (solar eclipses), or when only part of a body is eclipsed by the shadow (lunar eclipses). For solar eclipses, the viewer is in the penumbra part of the Moon's shadow.

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An annular eclipse is a total eclipse of luminary where a thin ring of light is visible around the intervening object. For solar eclipses, the viewer is in the antumbra part of the Moon's shadow. It is sheer coincidence that the Moon and Sun have nearly equal apparent sizes, making annular eclipses possible. Annular eclipses are ideal times for observing solar prominences.

Related Topics:
Antumbra - Solar prominence

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There is also another type of solar eclipse; the Hybrid solar eclipse. It consists of three phases. The eclipse starts as an annular one, then turns into a total and by the end it returns to the annular phase.

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An eclipse involving the Sun, Earth and Moon can only occur when they are in a line. Because the plane of the orbit of the Moon is tilted with respect to the plane of the orbit of the Earth (the ecliptic), eclipses occur only when the three bodies are near the intersection (the node) of these planes. The Sun passes either node once a year, and eclipses occur in a period of about two draconic months around these times. There can be from four to seven eclipses in a calendar year. They repeat according to eclipse cycles.

Related Topics:
Orbit - Ecliptic - Node - Year - Draconic month - Eclipse cycle

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Eclipse: Eclipse phases ►