cosmologyyy

• Light year


  The distance light would travel in one earth year
• Electromagnetic spectrum


  • Visible light
  • Other electromagnetic radiation
• Star's colour


  Can be used to infer its temperature
• Star


  Giant balls of hot gas mostly consisting of hydrogen and helium
• Constellation


  A group of stars forming a recognisable pattern
• Star cluster


  Group of stars held together by mutual gravitational attraction of each star
• Galaxy


  Huge star cluster, along with interstellar gas, dust, and dark matter
• Star formation in nebulae

  Interstellar dust, hydrogen and plasma cloud collapses under gravity
• Nuclear fusion


  Occurs in stars, where hydrogen nuclei combine to form helium due to gravity, releasing energy which powers the heat and light of a star
• Gravity


  Causes inwards force on star
• Radiation


  Causes outwards force on star
• Star's colour


  Indicates its temperature
• Spectral class


  Indicates the elements present, temperature and colour of a star
• Spectroscopy


  Used to analyse the light from stars to determine which chemical elements are present
• Main sequence star


  Stars lying on a line that runs from the top left to the bottom right of a HR diagram
• Stellar evolution of low mass star

  Hydrogen runs out, star expands and heats to become red giant, then collapses into planetary nebula (a gas cloud), then fades into super dense and hot white dwarf, then cools to black dwarf
• Stellar evolution of high mass star

  Starts as blue supergiant, cools to red supergiant, then collapses and explodes as supernova, leaving behind neutron star or black hole
• Elements more complex than hydrogen and helium are created by stars through nuclear fusion and supernova explosions
• Neutron star


  Super hot and dense remnant of a supernova explosion
• Black hole


  Singular, extremely dense remnant of a supernova explosion
• Hertzsprung-Russell diagram


  Shows the magnitude and temperature of stars, and how stars can change types through their life cycle
• Galaxy formation


  1. Formed out of immense clouds of gas and dust that collapsed under their own gravitational pull

  2. Many small lumps of matter clumped together
• Redshift and blue-shift explained by Doppler effect


  1. As stars move away, light waves are lengthened, appearing redder

  2. As stars move towards, light waves are compressed, appearing more blue
• Big Bang theory


  • Universe expanded rapidly from a single point to the infinite space today
  • Entire mass of the universe was compressed into a super hot, super dense ball smaller than an atom
  • Universe is 13.7 billion years old
• Steady State theory


  Originally, Steady State theory proposed the universe was stable and did not change over time and that Universe is infinite and has always existed in the same form, with new stars created at the same rate as old stars stop shining. Steady State theory was cast aside when Hubble discovered galaxies were moving away from each other
• Big Bang theory


  Universe expanded from a single point to infinite space, and is still slowly expanding