Eccentricity and Elliptical Orbits

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Eccentricity and Elliptical Orbits
All planets revolve around the Sun in an
elliptical orbit. The name of that shape is an
ellipse. An ellipse is an oval shape.
Ellipse
Eccentricity is the measure of how out of round
an orbit is. This means it is a number that
represents the shape of an orbit.
The eccentricity ranges from 0 to 1.
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The e 0.5
The e 0
The e 0.8
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e eccentricity d distance between foci L
length of the major axis
e d
L
L
f 1 and f 2 are each a foci. One focus is always
a star. Our solar system has the Sun as a focus.
d
f 1
f 2
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To draw an ellipse

1. You must carefully place two push pins in a piece
   of cardboard. The push pins must be the proper
   distance apart. Each push pin represents one
   focus. The distance between them is called the
   distance between foci.
2. Next, you must place your loop of string around
   both push pins.
3. Last, you must drag your pencil around the inside
   of the string.

This will create your ellipse.
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Helpful Hints
No Units

1. The eccentricity formula is on the front cover of
   your ESRTs.
2. An eccentricity close to the 1 means that the
   orbit is VERY elliptical. It looks like an oval
   shape. (The 1 looks like a straight line, and a
   shape like

is almost a straight line.)
3. An eccentricity close to zero means that the
orbit is NOT VERY ECCENTRIC or it is almost a
circle. (Zero looks like a circle )