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Naked-Eye Observing - Planets

Planets look like bright stars. The word "planet" means "wanderer," so defined because these wandering stars were thought to be just that. When telescopes looked at these objects more closely, it was discovered they were not stars, but the name stuck.

It is true that binoculars and telescopes are required to see any detail of the planets, but tracking the movement of these "wandering stars" can be done without any instrumentation.

This image is from Starry Night, a planetarium software package. It shows some brighter stars along the center of this image. Click to view a larger image, and to reveal the names of the planets in this image.

What is fascinating about the movement of the planets is that for a time, they will appear to move opposite the rotation of the celestial sphere. This is a result of the Earth overtaking the orbit of the planet (this only works for planets beyond the orbit of Earth) and is called retrograde motion. If the planet is moving along with the stars, this is called prograde motion.

 

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