PLANETS...
The objects that orbit the Sun are divided into three classes: planets, dwarf planets, and small Solar system bodies. A planet orbits only the Sun, and its mass is so large that its own gravitational pull is strong enough to compact it into a spherical shape, while also sweeping the region of its orbit relatively free of other objects. A dwarf planet is one that also orbits the Sun and is large enough to be roughly spherical, but is not large enough to clear the region of its orbit. Small Solar System bodies, such as most asteroids and comets, are too small for gravity to round off their irregular shapes.
The Solar System is the region of space that contains the Sun and all the celestial objects that fall within its gravitational influence. It consists of eight planets, a handful of dwarf planets, and a myriad of other smaller bodies including comets and asteroids. All of these orbit the Sun, a yellow star at the Solar System's center that has been shining for 4.57 billion years. Many of the planets have their own moons too, each an intriguing world in itself. Beyond the main planets lie the colder outer region of the Solar System. Here sits the Edgeworth-Kuiper Belt, a disc of small, icy, orbiting bodies. This merges further out in space with a vast cloud of comets, known as the Oort Cloud, which encompasses the entire Solar System.