the solar system

• Solar system


  The sun and the planets orbiting it
• Planets in the solar system

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


  • Mercury
  • Venus
  • Earth
  • Mars
• Gas giant planets


  • Jupiter
  • Saturn
  • Uranus
  • Neptune
• Beyond the orbit of Neptune there are dwarf planets, including Pluto
• Other objects in the solar system

  • Moons
  • Asteroids
  • Comets
• Moons


  Natural satellites that orbit planets
• Most planets in the solar system have at least one moon
• Galaxy


  A massive group of stars, such as the Milky Way which contains hundreds of billions of stars
• There are hundreds of billions of galaxies in the universe
• Star formation


  1. Cloud of dust and gas (nebula) collapses due to gravity

  2. Protostar forms as temperature rises

  3. Nuclear fusion starts, releasing energy

  4. Outward force from fusion balances inward force of gravity, star reaches equilibrium
• Nuclear fusion is the process where hydrogen nuclei join to form helium
• Gravity acts inwards on the star


  Fusion energy acts outwards on the star
• When the inward force of gravity is balanced by the outward force of fusion energy, the star is in equilibrium