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Orbital eccentricity (view source)
Revision as of 21:21, February 10, 2008
, 21:21, February 10, 2008→Definitions
For the general case of an [[ellipse]] having semi-major axis a and distance c from the center to either focus:
For the general case of an [[ellipse]] having semi-major axis a and distance c from the center to either focus:
<math>e = c/a</math>
A [[circle]] is a "degenerate" ellipse. In a circle, the two foci converge at the center. Therefore c = 0 and ''e'' = 0.
A [[circle]] is a "degenerate" ellipse. In a circle, the two foci converge at the center. Therefore c = 0 and ''e'' = 0.
A [[parabola]] is an extreme case of an ellipse and is the first open conic section. For any parabola:
A [[parabola]] is an extreme case of an ellipse and is the first open conic section. For any parabola:
<math>e = 1</math>
Therefore, for any closed orbit, 0 <= ''e'' <= 1.
Therefore, for any closed orbit, <math>0 <= e <= 1</math>.
== Practical application ==
== Practical application ==