Eccentricity

Eccentricity describes how elliptical (i.e., oval shaped) an orbit is. Eccentricity values range from 0 to almost 1. An eccentricity of 0 describes a perfectly circular orbit. The larger the eccentricity, the more elliptical the orbit.

Examples of orbital ellipses with different eccentricities.
Examples of orbital ellipses with different eccentricities. Modified from NASA illustration by Robert Simmon.

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