P5 - Astronomy

• Heliocentric model 


  Model that shows everything orbits the sun

  Disproved the geocentric model

  • created by Polish astronomer Nicoluas Copernicus
• Forces acting on star in the main sequence of its life cycle

  • Pressure from reactions (fusion) pushes out and gravity from star pushes in
  • they are balanced
• Planet

  Large rock object that orbits the sun

  • have cleared any larger object in its orbit
• Dwarf planet


  
  

  • Haven't cleared all larger objects in its orbit

  Aren't very large
• Moon 


  Natural satellite of a planet

  • Almost perfectly circular orbit (elliptical)
• Geocentric model


  Everything orbits earth

  • Early model by Greek astronomer Ptolemy
• Asteroids


  
  

  Huge lumps of rock and metal

  • Orbits the sun
• Comet


  
  

  Lumps of ice and dust that orbit the sun in an elliptical fashion

  Fast going up, slow as it goes down

  • Different diagonal plane orbit
• How Galileo used telescopes to prove heliocentric model


  
  

  Telescopes invented in 16th century

  • helps scientist see into space better/ in detail

  Galileo discovered that Jupiter has moons that orbit it

  • plotting their movement showed not everything orbits earth
• How telescopes can be used to detect EM radiation

  Different telescopes can detect EM radiation

  Telescopes that detect x-rays, radio waves and infrared radiation

  • placed in earths orbit as earth's atmosphere absorbs them
• Weight 


  Force of gravity acting upon the mass of an object
• Gravitational field strength on earth 10N/kg
• Speed of low orbit satellite

  Fast to stay in orbit

  If slow by contact with air from atmosphere

  • fall towards earth
• Larger the mass = stronger the gravitational field strength
• Life cycle of stars similar to our sun

  
  

  • Nebula
  • Protostar
  • Main sequence star
  • Red giant
  • White dwarf
  • Black dwarf
• Life cycle of a massive star


  
  

  • Nebula
  • Protostar
  • Main sequence star
  • Red supergiant
  • Supernova
  • Neutron star or Black hole
• Dopplers effect as a moving object emits sound


  
  

  Higher pitch

  • waves in front get compressed making wavelength smaller

  Lower pitch

  • waves behind expand making wavelength larger
• Proof that universe is expanding

  
  

  Edwin Hubble investigated patterns of dark lines

  • looked in all directions of space
  • they emitted red shift

  Therefore

  • larger red shift
  • they were moving away at fast pace
• Big Bang theory


  • 1920
  • All matter/energy contained in space smaller than an atom

  Crunching cause an explosion

  • energy sent out in many directions
  • kept expanding

  Gravity caused dust to clump together creating stars

  • stars clump together to create galaxies
• Steady state theory 


  • 1948
  • Universe always existed
  • It expands as new matter is created
  • No beginning or end to universe
  • Density is always the same
• Cosmic microwave background radiation (CMB)


  
  

  High energy gamma radiation created after big bang

  • expanded into universe

  As universe expanded which caused waves to expand

  • wavelength increased
  • microwaves

  Mapped by microwave detectors on ground/satellites
• State evidence for big bang 


  • Red shift
  • CMB radiation
• State evidence for steady state theory 


  Red shift
• Solar system

  Mercury, Venus, Earth, Mars, (asteroid belt), Jupiter, Saturn, Uranus and Neptune

  (Pluto is a dwarf planet)
• Larger the radius = the weaker the gravitational field strength is
• The closer the orbit of an object = the quicker it has to move
• Nebula --> Protostar (Life cycle of a average/massive star)

  
  

  Nebula

  • cloud of gas, ash and dust

  Protostar

  • gravity causes them to pulled together = becomes stronger and denser
  • nuclear fusion of hydrogen creates helium = energy release 
•  Main sequence star (Life cycle of a massive star)

  
  

  Stable

  • pressure from reactions balance gravity being pulled inwards

  Eventually hydrogen in core begins to run out and begins to crunch

  • core collapses
  • outer layer expands to create a red giant/supergiant
• Average stars = red giant

  Massive stars = red supergiant 

  Surface cools = become red
• White dwarf (Life cycle of a average star)

  
  

  Red giant outer layer ejected

  • solid core is left
  • this will cool to make a black dwarf
• Supernova explosion (Life cycle of a massive star)

  
  

  
  

  Atoms in red supergiant fuse nuclei

  • make heavier elements
  • expand/contract as balance shifts

  Explosion

  • creates neutron star/black hole
• Neutron star/Black hole (Life cycle of a massive star)

  
  

  Neutron star

  • very dense core

  Black hole

  • when a very large star collapses
• Natural Satellites


  
  

  Moons that orbit planets
• Artificial Satellites


  Man-made satellites that have been sent into space for purposes

  • satellite imaging and communications
• The solar system investigated using space probes
• Telescopes


  • Orbit around the earth

  Give much clearer images than ground based telescopes

  • clouds and dust in the air don't interfere with images
• Invention of photography

  Allowed astronomers to make more detailed observations and measurements

  • computers further increased this
• Satellite forces

  Moving object carry on moving in a straight line

  • until a force acts on it
  • can change direction or speed
• Satellite forces

  Satellite orbits earth

  • gravitational force between the 2 is always to the centre

  Centripetal force

  • at a right angle to direction of movement
  • causes directional change
• Artificial satellite


  Orbit earth and have a fairly circular orbit (elliptical)