The Solar System

• The Solar System consists of:

  • The Sun
  • Eight planets
  • Natural and artificial satellites
  • Dwarf planets
  • Asteroids and comets
• The Sun lies at the centre of the Solar System

  • The Sun is a star that makes up over 99% of the mass of the solar system
• There are eight planets and an unknown number of dwarf planets which orbit the Sun

  • The gravitational field around planets is strong enough to have pulled in all nearby objects with the exception of natural satellites
  • The gravitational field around a dwarf planet is not strong enough to have pulled in nearby objects
• The 8 planets in our Solar System in ascending order of the distance from the Sun are:

  • Mercury
  • Venus
  • Earth
  • Mars
  • Jupiter
  • Saturn
  • Uranus
  • Neptune
• There are two types of satellite:

  • Natural
  • Artificial
• Some planets have moons which orbit them

  • Moons are an example of natural satellites
• Artificial satellites are man-made and can orbit any object in space

  • The International Space Station (ISS) orbits the Earth and is an example of an artificial satellite
• Asteroids and comets also orbit the sun
• An asteroid is a small rocky object which orbits the Sun

  • The asteroid belt lies between Mars and Jupiter
• Comets are made of dust and ice and orbit the Sun in a different orbit to those of planets

  • The ice melts when the comet approaches the Sun and forms the comet’s tail
• The objects in our solar system

  A) sun

  B) asteroid belt

  C) mercury

  D) venus

  E) earth

  F) mars

  G) rocky planets

  H) jupiter

  I) saturn

  J) uranus

  K) neptune

  L) gas planets

  M) pluto

  N) dwarf planet

  O) moon

  P) natural satellite

  Q) artificial satellite

  
• You need to know the order of the 8 planets in the solar system

  • The following mnemonic gives the first letter of each of the planets to help you recall them: My Very Excellent Mother Just Served Us Noodles
  • Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune
• There are 4 rocky and small planets: Mercury, Venus, Earth and Mars

  • These are the nearest to the Sun
• There are 4 gaseous and large planets: Jupiter, Saturn, Uranus and Neptune

  • There are the furthest from the sun
• The eight planets of our Solar System

  A) mercury

  B) venus

  C) earth

  D) mars

  E) jupiter

  F) saturn

  G) uranus

  H) neptune

  
• The differences in the types of planets are defined by the accretion model for Solar System formation
• The Sun was thought to have formed when gravitational attraction pulled together clouds of hydrogen dust and gas (called nebulae)
• The Solar System then formed around 4.5 billion years ago

  • The planets were formed from the remnants of the disc cloud of matter left over from the nebula that formed the Sun
  • These interstellar clouds of gas and dust included many elements that were created during the final stages of a star's lifecycle (a previous supernova)
• Gravity collapsed the matter from the nebula in on itself causing it to spin around the Sun

  • The gravitational attraction between all the small particles caused them to join together and grow in an accretion process
• A rotating accretion disc is formed when the planets emerged
• The accretion model of the creation of the Solar System

  A) nebula

  B) hotter

  C) cooler

  D) million years

  E) rocky

  F) icy bodies

  G) 100 million

  H) years

  
• As the Sun grew in size it became hotter
• Where the inner planets were forming near the Sun, the temperature was too high for molecules such as Hydrogen, Helium, water and Methane to exist in a solid state

  • Therefore, the inner planets are made of materials with high melting temperatures such as metals (e.g. iron)
  • Only 1% of the original nebula is composed of heavy elements, so the inner, rocky planets could not grow much and stayed as a small size, solid and rocky
• The cooler regions were further away from the Sun, and temperature was low enough for the light molecules to exist in a solid state

  • The outer planets therefore could grow to a large size up and include even the lightest element, Hydrogen
  • These planets are large, gaseous and cold
• When referring to the accretion model for the formation of the Solar System, make sure your answer has the following:

  • the model’s dependence on gravity
  • the presence of many elements in interstellar clouds of gas and dust
  • the rotation of material in the cloud and the formation of an accretion disc
• Mnemonic for the order of the planets

  My very excellent mother just served us noodles (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune)
• What planets are gaseous?

  Jupiter, Saturn, Uranus, Neptune
• What is an accretion disc?


  A disk of gas and dust that orbits around a central object, such as a star or black hole.