Which is the Largest Planet In our Solar System: Solar System is the largest and sophisticated system of the this universe which consist of 8 planets which are 4,568 billion years old. It is fifth planet from the sun. From all thePlanets Jupiter is the largest Planet in all the universe. Mainly it is composed of Gaseous and liquid matter. It has the diameter of 142,984 Km at its equator. According to a deep study and research its clearly mentioned that its upper atmosphere is 88 to 92% made of hydrogen while 8 to 12 % helium.