Astronomy Picture of the Day

Three Years of Saturn

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#99494 by @ 08.04.2007 00:00 - nach oben -
Three Years of Saturn


Using an image recorded just last month as a base,
this composite illustration tracks the
motion of bright Saturn as it wanders
through planet
Earth's night sky.

Starting at the upper right, Saturn's position is shown about
every two weeks beginning in August 2005 and projected
through September 2008.

Over the three year period, Saturn actually appears to reverse
its general eastward (leftward) drift,
tracing out three flattened curves.

The periodic backwards or
retrograde motion with
respect to the background stars is a
reflection of the motion of the Earth itself.

Retrograde motion can be seen each time Earth overtakes
and laps planets orbiting farther from the Sun, the
Earth moving more rapidly through its own
closer-in orbit.

The Beehive star cluster in Cancer
lies near the track at the upper right.

Stars along the "backward question mark" at the head
of Leo
are in the left half of the frame.

Saturn's position
is near the right hand limit
of the middle curve.

Click on the picture to download and view the gif animation.

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