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.
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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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