Celestial Mechanics and the Solar System

Viewed from the Earth, the Sun moves eastward on its annual journey relative to the Zodiac.

Mercury and Venus (the Inner Planets) move eastward of the Sun appearing higher and higher in the western sky after sunset, as an evening star.

At greatest eastern elongation (the maximum angular distance east from the Sun) it then moves closer to the western horizon, moving closer to the Sun. Eventually moving west of the Sun, it rises as a predawn morning star in the eastern sky. During the switch from evening to morning star, Venus and Mercury move westward with respect to the stars, in retrograde motion.

The Outer Planets, Mars, Jupiter, Saturn; progress steadily eastwards until the y approach opposition (180° away from the Sun in the sky). They appear to slow and halt before tracing a retrograde loop towards the west, slow to another halt, and resume their eastward motion. Puzzling?

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~ by jamesdow2013 on March 27, 2013.

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