开普勒发现了行星运动的三大定律。

___Kepler discovered the three laws of planetary motion.

根据开普勒定律，行星的轨道是椭圆形的。

According to ___Kepler's laws, planetary orbits are elliptical.

开普勒望远镜发现了许多可能适合居住的行星。

The ___Kepler telescope has found many potentially habitable planets.