Space

• Sun


  A star
• Location of the sun

  Centre of the solar system
• How the sun releases energy

  The process of nuclear fusion
• Number of planets in the solar system

  8
• Number of dwarf planets orbiting the sun

  5
• Galaxy our solar system is part of

  Milky Way galaxy
• Number of stars in our galaxy

  200,000 million stars
• Many of these stars each have their own system of planets
• What makes up the universe

  Billions of galaxies
• When the solar system was formed

  4.6 billion
• Process of birthing a star

  1. A large cold cloud of dust and gas (nebula) collapses due to gravity

  2. Atoms and molecules move quickly, transferring kinetic energy to thermal energy

  3. The collapsing and heating ball of gas is called a protostar

  4. When temperature is high enough, hydrogen nuclei can collide and fusion begins, a star is born
• Fusion reactions inside stars

  Lead to an equilibrium
• Outward forces from nuclear fusion

  Balance the gravitational forces tending to collapse the star
• Main sequence star


  A stable star producing energy by fusing hydrogen nuclei
• How a star ends its life

  Depends on its size
• How stars about the same size as the sun die

  1. Towards the end of the star's life, the supply of hydrogen begins to run out

  2. The core becomes hotter and helium can now fuse to form heavier elements

  3. The hot core causes the outer surface to swell into a red giant

  4. Eventually, fusion reactions can no longer happen and the star collapses to form a white dwarf, which then cools down to become a black dwarf
• Red giant


  A very large star which fuses helium into heavier elements
• White dwarf


  A star at the end of its life, with no fusion occurring, just cooling down
• Black dwarf


  A white dwarf that has cooled down
• How stars much larger than the sun die

  1. The star collapses in the same way as a smaller star but forms a red super giant

  2. The red super giant is able to fuse nuclei to form elements as massive as iron

  3. When the red super giant runs out of nuclear fuel it collapses very quickly, creating high temperatures that cause the star to explode in a supernova

  4. The supernova explosion creates elements with atomic numbers higher than iron, and the remnants of the supernova formed our solar system

  5. The rapid collapse of the centre of the star creates a neutron star or black hole
• Red super giant


  A large red giant which has a very hot core that can produce elements as heavy as iron by fusion
• Supernova


  A gigantic explosion caused by runaway fusion reactions
• Neutron star


  A very small dense star made out of neutrons
• Black hole


  The most concentrated form of matter from which not even light can escape
• Movement of moons and planets

  In nearly circular orbits
• What causes planets to orbit the sun

  Gravity
• What causes the moon and artificial satellites to orbit the Earth

  Gravity
• Gravity acting on the moon


  Makes it change direction
• The speed of the moon is not constant
• Sound moving away from us

  We hear a lower frequency and the wavelength of the waves increases
• A light source moving away from us

  The wavelength of the light increases and moves towards the red end of the spectrum (red-shifted)
• Edwin Hubble discovered that light from distant galaxies is red-shifted, so they are moving away from us, and the further a galaxy is away, the greater the red-shift and the greater the speed
• Edwin Hubble's idea led to the Big Bang theory
• The Big Bang theory


  The Universe began as a very small region that was extremely hot and dense, which then exploded, throwing matter outwards; the matter that moved the fastest has travelled the furthest away from the original explosion, suggesting that at one instant, a long time in the past, all the galaxies were in the same position