The square of the orbital period of a planet is directly proportional to the cube of the semi-major axis of its orbit.
第三定律（周期定律）：各个行星绕太阳公转周期的平方和它们的椭圆轨道的半长轴的立方成正比。
When the planetary migration occurs under the tidally interaction of a planet and a disk of gas or a planetesimal, the orbital parameters, especially, semi-major axis, of this planet will be altered.
行星迁移发生在行星与气体或星子的星盘之间进行潮汐相互作用时，这造成行星轨道参数，特别是半主轴的变更。
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