T8: hertzsprung

• apparent luminosity?

  how bright stars appear not taking in account the distance
• absolute luminosity?

  how bright stars appear if they are same distance from observer
• luminosity scale?

  • bright = -10
  • dim = 10
• graph?

  • y axis = luminosity
  • x axis = temperature
• as luminosity decreases, the temperature decreases
• apparent magnitude = how bright a star appears
• absolute magnitude = measures how bright a star is at the same distance from earth
• big bang = 14 billion years ago = matter was very small and dense - then exploded and continues to expand since
• evidence to support big bang:

  • light spectra from distant galaxies = wavelength of light has become longer - stretching
  • galaxies producing light moving away
• Doppler effect = the apparent change in frequency of a wave as it is travelling towards or away from the observer
• doppler effect:

  • towards: shorter wavelength - increasing frequency
  • away: longer wavelength - decreasing frequency
• higher pitch as sound approaches, lower pitch as moves away
• further way a galaxy is = greater its red-shift = moving faster away