Quote:
Originally Posted by Stargazer_10
Just wondering why planets orbit the sun elliptically? Why is it not circular?
Thanks for the help in addition.
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A circle is the special case of an ellipse where it has eccentricity zero. The general formula for an ellipse is
(x/a)^2 + (y/b)^2 = 1 with a>=b
The eccentricity is e = sqrt(1-(b/a)^2) and will be less than 1
If a and b are equal e will be zero. As a and b are equal we can rename them both in the formula as "r". Multiply both sides by r^2 and you get the usual formula for a circle
x^2 + y^2 = r^2
Even if a planet at some stage had a circular orbit, perturbations from the gravity of all the other objects would very quickly change the orbit to make it elliptical.