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orbital eccentricity

 Definition/Summary Eccentricity is the measure of the 'roundness' of the orbit. For circular orbits: e=0 For elliptical orbits: 01

 Equations $$e= \frac{c}{a}$$ For ellipses: $$e = \frac{r_A-r_P}{r_a+r_P}$$ $$e = \sqrt{ 1- \left ( \frac{b}{a} \right )^2}$$ For hyperbolas: $$e = \sqrt{ 1 + \left( \frac{b}{a} \right)^2}$$

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 Recent forum threads on orbital eccentricity

 Breakdown Physics > Astro Cosmo >> Celestial Mechanics

 See Also eccentricity

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 Extended explanation a is the semi-major axis of the orbit. For an elliptical orbit, this is equal to one half the longest length of the ellipse. For an hyperbolic path, it is equal to the distance of periapsis to to point where the asymptote lines cross (the center of the hyperbola). b is the semi-minor axis of the orbit. For an elliptical orbit, this is equal to one half the width of the ellipse. See attached image for a hyperbolic orbit. c is the distance between the center and the focus of the orbit. rA is the apoapsis distance as measured from the focus. rP is the periapsis distance as measured from the focus.

Commentary

 Mammo @ 06:24 AM Dec9-08 The 100,000 year glacial cycle found in ice-core data is attributed to the climate forcing produced by the Earth's orbital eccentricity around the Sun. The exact mechanisms for the climate forcing are still unresolved and have been perplexing Earth scientists for decades.