space (p8) - triple

• Components of the solar system

  • One star (the Sun)
  • Eight planets
  • Dwarf planets
  • Natural satellites (moons)
  • Asteroids
  • Comets

  
• Heliocentric


  The sun lies at the centre of our solar system
• Planets in the solar system

  • Mercury
  • Venus
  • Earth
  • Mars
  • Jupiter
  • Saturn
  • Uranus
  • Neptune
• Planets

  • Smaller planets are made of primarily rock, then the larger planets are primarily gas
  • All planets orbit the Sun on the same plane
  • All planets rotate, just at different speeds
  • Some planets rotate in the opposite direction or on a skewed axis to the other planets, and this may be due to past collisions throwing its axis off balance
  • Larger planets have rings, as their gravitational field is so strong it attracts debris
• Geocentric model

  Initially, Earth was at the centre, the planets, our moon, and the sun, orbited the Earth
• Heliocentric model

  The sun at the centre, with the main evidence being Mars' "retrograde motion"
• As the planet orbits the sun

  The gravitational force causes the planet to change direction constantly (it moves in a circle around the sun), so the velocity is always changing
• If the planet moves closer to the sun (orbital radius decreases)

  The gravitational attraction to the sun increases, so the orbital speed of the planet increases
• Life cycle of a star

  1. Dust and gas cloud is present in a galaxy

  2. The gravitational attraction between the gas/dust particles draws them together

  3. The cloud becomes more concentrated, as the particles get closer

  4. The temperature and pressure of the cloud increases as the particles get pushed so close together

  5. Eventually the pressure gets so great that the gas/dust particles are able to fuse together, creating a large amount of energy, which opposes the collapsing of the cloud due to gravity, forming a star

  6. Eventually the star runs out of gas to fuse, so it collapses, and if massive, produces a supernova, leaving a neutron star or black hole, or if normal-sized, produces a planetary nebula, leaving a white dwarf

  
• Red shift

  Light appears red shifted from galaxies which are moving away from Earth, evidence of an expanding universe
• Evidence for the Big Bang

  • Red shift
  • Cosmic Microwave Background radiation
• As the big bang accounts for all the experimental evidence, it is the most accepted model currently
• There is much about the universe that is not understood, for example dark mass and dark energy
• for a stable orbit

  if the planet moves closer to the sun the gravitational attraction to the sun increases so the orbiotal speed of the planet increases
• nebula

  All stars form from a giant cloud of hydrogen gas and dust
• protostar

  The force of gravity within a nebula pulls the particles closer together until it forms a hot ball of gas as the particles are pulled closer together the density of the protostar will increase. This will result in more frequent collisions between the particles which causes the temperature to increase
• main sequence star

  the protostar becomes hot enough, nuclear fusion relations occur within its core, the hydrogen nuclei will fuse to form hellium nuclei

  every fusion reaction releases heat energy which keeps the core hot
• Red giant formation

  1. Hydrogen fusion reactions in the star begin to run out

  2. Fusion reactions in the core start to die down

  3. Core shrinks and heats up

  4. Inward force of gravity becomes greater than outward force of expanding gases

  5. New fusion reactions occur around the core (e.g. helium to beryllium)

  6. Outer part of the star expands

  7. Star becomes a red giant
• The star is red because the outer surface starts to cool
• planetary nebula

  Once this second stage of fusion reactions have finished, the star will become unstable and eject the outer layer of dust and gas
• white dwarf

  • The core which is left behind will collapse completely, due to the pull of gravity, and the star will become a white dwarf
  • The white dwarf will be cooling down and as a result, the amount of energy it emits will decrease
• black dwarf

  • Once the star has lost a significant amount of energy it becomes a black dwarf
  • It will continue to cool until it eventually disappears from sight