Space physics

• Satellite 


  Anything that orbits a body due to gravity

  can be natural e.g moon or artificial e.g hubble telescope
• Solar system


  8 planets orbiting the sun in elliptical orbit
• Asteroids


  Mostly made of rock and metal

  found mainly in the asteroid belt between mars and Jupiter
• Comets 


  Are made mostly of ice and dust

  have much more elliptical orbits
• Galaxy 


  Ours is the milky way

  they are massive collections if billions of stars (which have own solar systems)

  held together by gravity
• Universe


  Scattered with galaxies

  mostly empty space
• nebula


  Cloud of dust and gas pulled together by gravity to form a protostar
• Protostar


  As more gas and dust join it gets bigger making gravity increase

  this means it becomes more dense = temperature increases as more collisions

  when temp and pressure high enough hydrogen atoms fuse to form helium nuclei keeping core hot
• Main sequence star


  Outward pressure from energy of nuclear fusion is balanced by inward pressure of gravity = long stable period

  our sun is currently here

  slowly runs out of hydrogen so gravity pushes it into a small ball = nuclear fision starts making heavier elements up to iron and expands again
• Red giant


  If star was small/medium before then it becomes a red giant

  Becomes unstable after a while and expels it’s outer layers of dust and gas

  leaving behind a hot dense solid core
• White dwarf 


  Hot dense solid core

  gives of bright white light and relatively small

  over time it gets cooler and darker as it emits all its energy
• Black dwarf 


  No longer has enough energy to release light
• Red Super giant


  If star was really big before then turns into a red super giant

  start to shine brightly again as more nuclear fusion occurs

  go through several cycles of expansion + contraction

  eventually explodes
• Supernova 


  Forms elements heavier than iron and ejects them across the universe
• neutron star


  If star was big that causes supernova it condenses into a dense core = neutron star
• Black hole


  If star was massive that caused supernova it can collapse in on itself forming a black hole
• How does black hole work

  It’s gravity is able to pull in any light that passes nearby so it appears as empty space
• Orbits


  Curved path of one celestial object or space craft around another celestial object
• How do things stay in orbit ?

  Newtons 1st law: an object travelling at a certain velocity will continue at that velocity unless acted upon by a resultant force

  so when a satellite is travelling the force of gravity from the celestial body is only strong enough to change its direction

  so It constantly stays orbiting earth

  but because of velocity equation and the speed being the same and direction constantly changing the satellite is accelerating
• Red shift 


  Light waves are stretched as they make their way to earth

  as distant galaxies are moving away so wavelengths are stretched shifting it to the red end of spectrum (galaxies aren’t moving through spaces but space between us is expanding)
• Beginning of the universe


  All matter in the universe existed in a tiny dense and hit space the exploded and started to expand
• Cosmic microwave background radiation CMBR

  Is electromagnetic radiation that’s observed in all directions

  initially radiation from the Big Bang was very hot but as expanded it cooled and dropped in frequency
• Redshift equation 


  Difference in obsevered and original wavelength divided by original wavelength = recessional velocity of galaxy divided by speed of light in vacuum