Planetary systems are complex systems of celestial bodies that orbit around a central star or stars. They range from just a few planets to hundreds or even thousands of objects. Our own planetary system, the solar system, is dominated by eight major planets that revolve around the Sun, four of which are rocky and four of which are gas giants. In addition to the planets, the solar system is home to a number of dwarf planets, comets, asteroids, and other objects. Planetary systems are formed from the collapse of a giant cloud of gas and dust, with gravity pulling the matter together to form planets and other objects. The study of planetary systems is an important area of research in astronomy and astrobiology, as it provides insights into the origin and evolution of planets, the conditions necessary for life, and the likelihood of finding other habitable worlds in the universe.