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Plane of the Ecliptic

Photo: Moon, Saturn, Mars, and Mercury in a row

The plane of the ecliptic is illustrated in this Clementine star tracker camera image that reveals, from right to left, the moon, the sun's corona rising over the moon's dark limb, and the planets Saturn, Mars, and Mercury. The ecliptic plane is defined as the imaginary plane containing the Earth's orbit around the sun. In the course of a year, the sun's apparent path through the sky lies in this plane. The planetary bodies of our solar system all tend to lie near this plane, since they were formed from the sun's spinning, flattened, proto-planetary disk.

Photograph courtesy NASA