The solar system

• Solar System


  Planetary system consisting of a star (the Sun) and all the objects orbiting it, including planets, moons, dwarf planets, asteroids and comets
• The Sun


  • At the centre of the Solar System
• Planets and moons orbiting

  1. Planets orbit the Sun

  2. Moons orbit planets
• Asteroid belt


  Region between the orbits of Mars and Jupiter where there are thousands of rocky asteroids and dwarf planets
• Dwarf planet


  Body similar to a planet but too small to be called a planet. Pluto is an example.
• Comet


  Formed from ice and dust beyond the orbit of Neptune, have highly elliptical orbits
• The Sun is not the only star with planets, other stars have planets in their planetary systems
• Planets in the Solar System

  • Mercury
  • Venus
  • Earth
  • Mars
  • Jupiter
  • Saturn
  • Uranus
  • Neptune
• Inner planets


  • Rocky planets
• Outer planets


  • Gas giants
• As the distance from the Sun increases, the time for one orbit increases
• As the distance from the Sun increases, the temperature decreases, except for Venus which has a thick atmosphere that keeps more heat in
• Formation of the Solar System

  1. Cloud of gas, mainly hydrogen and helium, and dust ejected from a supernova

  2. Gravitational forces caused the cloud to collapse and the particles to collect together

  3. As the cloud collapsed it began to spin, turning into a disk

  4. The centre of the disk became the Sun and the rest collected together to form the planets

  5. The inner planets are rocky because it was too close to the Sun for the light gaseous elements to condense, so they were pushed further away

  6. The outer planets are gaseous because it is further from the Sun and the gaseous elements were able to condense and collect to form the gas giants
• Distances in space are so large that it is impractical to use meters or km, so different units are used: Astronomical unit = the mean distance from the Sun to the Earth (approximately 150,000,000 km), Light year = the distance light travels in one year