All planets began as small cometary-like stars that now have evolved into the second, third, fourth, or fifth stage of spherical planetary evolution at rates in full accord with size and time. The best-known examples are, respectively, Jupiter (gaseous), Uranus (transitional), Earth (rocky), and Mercury (inactive). Planets are self-sustaining entities, generally revolving around a larger central mass while evolving through five observable stages of evolution (E) via internal nucleo-synthesis (IN) and in full compliance with natural laws of planetary systems; e.g., the laws of planetary motion, gravity, and the ongoing energy-matter relationship expressed as E=mc2(?). Other than different rates of evolution and subsequent variations in compositional matter, spherical size is immaterial. However, in every case, IN and E are crucial: one cannot exist without the other during the billions of years of transformation of their nuclear energy cores into planetary matter.
This paper is aka "What Are Planets?"
