T8: astrophysics

• hottest to coolest star?

  blue, white, yellow, orange, red
• blue star?

  • hottest
  • surface temperature of >33000
• white star?

  • second hottest
  • 10000 - 7500
• yellow star?

  • third hottest
  • 6000 - 5200
• orange star?

  • second coolest
  • 5200 - 3700
• red star?

  • coolest
  • <3700
• life cycle of small star?


  1. stellar nebula
  2. average star (main sequence)
  3. red giant
  4. death of star
  5. white dwarf
• life cycle of large star?


  1. stellar nebula
  2. massive star (main sequence)
  3. red supergiant
  4. supernova
  5. smaller: neutron star, bigger: black hole
• smallest to largest space objects?

  plants, stars, universe, galaxy, satellites, solar systems
• solar system?


  a star and the planets that orbit it
• galaxy?


  collection of billions of stars (solar systems)
• universe?


  the collection of all the billions upon billions of galaxies
• speed of light = 300000000 m/s
• orbit?


  when an object goes around another object
• why do planets orbit stars?

  • gravitational field caused by sun
  • force increased by being closer to object OR object having more mass
• circular orbits?


  • objects go around in circle
  • constant speed
  • constant distance from centre
• elliptical orbits?

  • objects go around in ellipses (oval)
  • speed varies (closer to sun = fastest)
  • not constant distance from centre
• gravitational force?

  • causes moon to orbit planet
  • causes planets to orbit sun
  • causes satellites to orbit the Earth
  • causes comets to orbit the sun
• orbital speed = (2 x pie x orbital radius) / time period
• why can't the moon be shown on the H-R graph?

  it is a natural satellite that orbits another planet