There are eight planets in the Solar System. From closest to farthest from the C, they are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. The first four planets are called terrestrial planets. They are mostly made of rock and metal, and they are mostly solid.Planetary systems come from protoplanetary disks that form around stars as part of the process of star formation. During formation of a system much material is gravitationally scattered into far-flung orbits and some planets are ejected completely from the system becoming rogue planets.