Solar System Facts

The solar system was formed approximately 4.6 billion years ago by the collapse of a giant molecular cloud. The mass at its centre collected to form the Sun and a flat disk of dust around it. This eventually formed the planets and other bodies of the solar system.

  • The solar system consists of the Sun, planets, dwarf planets, moons, and numerous smaller objects such as comets and asteroids.
  • 194 moons, 3,583 comets and 796,289 asteroids have been found in the solar system.
  • 99.86% of the solar system’s mass is found in the Sun. The majority of the remaining 0.14% is contained within the eight planets.
  • The four smaller inner planets, also known as the “terrestrial planets”, are primarily composed of rock and metal.
  • The four outer planets, also known as the “gas giants”,  are substantially larger and more massive than the inner planets.
  • The two innermost gas giants, Jupiter and Saturn, are the largest of the four outer planets and are composed mainly of hydrogen and helium.
  • The two outermost gas giants, Uranus and Neptune, are composed largely of ices (water, ammonia and methane).  Together they are referred to as the “ice giants“.
  • Other structures of note in the solar system the Asteroid Belt, Kuiper Belt and Oort Cloud.

Facts about the Solar System

See the planets and the dwarf planets pages for more information or click an image below to find out more about the solar system’s structure:

Choose one of the following to learn about different objects and events in the solar system:

Last Updated: February 2021, First Published: June 2012
Author: Chris Jones