Space

• Protostar


  Cloud of dust and gas where stars initially form
• Star formation


  1. Cloud of dust and gas pulls together to form a protostar

  2. Temperature and density increase as more particles collide

  3. Nuclear fusion begins, heating the core
• Main sequence star


  • Outward force from nuclear fusion balances gravity, stable period lasting billions of years
• Life cycle of a small-to-medium star

  1. Hydrogen runs out, star expands into red giant

  2. Outer layers ejected, leaving behind a white dwarf
• Life cycle of a large star

  1. Undergoes more fusion, expands and contracts several times

  2. Eventually explodes in a supernova, forming elements heavier than iron
• Neutron star


  Very dense core left behind after a supernova explosion
• Black hole


  Super dense point in space that even light cannot escape
• The Solar System has one star - the Sun
• Objects in the Solar System

  • 8 planets
  • Dwarf planets
  • Moons
  • Asteroids
• The Solar System is a tiny part of the Milky Way galaxy
• Gravity


  The force that creates orbits
• Orbits


  1. Object constantly changes direction, accelerating towards the centre

  2. Velocity changes but speed remains constant

  3. Gravitational force keeps object in a circular orbit
• Orbital speed


  Faster moving objects have smaller orbits
• The universe appears to be expanding
• Red-shift


  Increase in the wavelength of light from distant galaxies, indicating they are moving away
• More distant galaxies have greater red-shifts, indicating they are moving away faster
• Big Bang theory


  The universe started from a very small, dense and hot space that then expanded
• New evidence may change our theories about the universe
• Dark matter and dark energy are not well understood