The Sun and the Solar System

• Milky Way Galaxy — contains billions of solar systems and stars
  • - Small island in the vast universe
  • - Vast possibilities
    
    
• Solar system — all heavenly bodies associated with one star
  • Ours is known as "Sun"
    - dominated by sun’s gravitational attraction
    - 9 major planets (reflect light rather than produce it)
    - other bodies: comets, moons, meteors, meteorites
    

The Planets

• Comparisons make Earth a "moderate" place to live
  

• Mercury - closest to the sun
  • - only 5% Earth’s mass, yet large core
  • - no atmosphere
  • - rotates on axis every 59 days; yet 88 days full year
  • - temp. extremes 840°F (11 times brighter and -300°F
    
• Venus - Earth's twin - same size, density and mass
  • - 96% carbon dioxide layer allows little energy to escape
  • - no liquid or frozen water
  • - temps. extremes of 850 degree F.
    
• Earth - factors for "special and life sustaining"
• - Distance (avg. of 93 million miles)
• - Movement around sun & within its Earth's axis
• - Atmosphere (key to survival)
  - only planet to convert sun's energy into life
  
  
• Mars - our closest planet
  • - newly detected water (rocks & visibly scoured landscapes)
  • - thin atmosphere composed mostly of carbon dioxide (95%)
  • - vast temp fluctuations (-190 to 77 F)

   

  More distant planets - insufficient solar radiation to support life: -Uranus, Neptune and Pluto Liquid and gaseous planet (mostly helium and hydrogen; no oxygen; no walking surfaces) - Jupiter, Saturn

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