One characteristic of Earth's orbit is its eccentricity, the degree to which the orbit is an ellipse rather than a circle.
地球轨道的一个特点是它的离心率，也就是轨道是椭圆而不是圆形的程度。
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Where a perfect circle has an eccentricity value of zero, roughly half of exoplanets seen thus far have an eccentricity of 0.25 or greater.
一般一个完美圆周的偏心值为0，而约有一半的系外行星的偏心值在0.25或者更高。
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The determination of eccentric circleEccentricity is-further discussing, and it's design process is to provide a reliable theoretical basis for designing and applying correctly.