Second, the detailed reasons:
1. Kepler's first law (orbital law): all planets orbit the sun in elliptical orbits of different sizes, and the sun is at a focus of these ellipses;
2. Kepler's second law (also known as the law of area): the connecting line between the sun and the planet sweeps the same area in the same time;
3. Kepler's third law (also known as the periodic law): the ratio of the third power of the semi-long axis of the elliptical orbit of all planets to the second power of period of revolution is equal;
Kepler's Law 123 also applies to artificial satellites.
Under the action of gravity, there are only two situations in which a planet moves around a star or a satellite moves around a planet: an ellipse or a hyperbola, of which only an ellipse is stable. A circle is just a special case where the major axis of an ellipse is equal to the minor axis.