Question

why are orbits of planets elliptical

Answer 1

Prior to Newton, Kepler showed by measurement that the observable planets hadelliptical orbits. Ellipses are closed so the planets we see in elliptical orbits stick around. A circle is a special case of an ellipse and it is theoretically possible for anorbit to be circular.

Answer 2

Planets rotate around the Sun because of the curve in the space they should follow a circular path and the distance between planet and Sun should be at a distance. Given the fact that earth has a elliptical orbit around the sun, and the distance between Earth and Sun varies according to position of the earth.

Hope it will help you :-)