Rajasekharan Rajagopalan wants to know:Why [do] comets orbit the Sun in a parabolic path, unlike planets which orbit in an elliptical one? (Parabolic, by the way, is an unbound orbit that's exactly on the border between elliptical and hyperbolic.) NASA / JPL-CaltechThe secrets of what makes a comet, asteroid, or an object beyond our Solar System orbit the way it does? Objects stably in our Solar System, particularly after 4.5 billion years, are all moving in elliptical orbits around the Sun. Our Solar System is continuously depopulating over time, and has fewer objects in its asteroid belt, Kuiper belt, and Oort cloud than ever before.

Source: Forbes December 09, 2017 15:33 UTC