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The Solar System

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Our Solar System

  • Heliocentric system (sun-centered):
    • Planets, asteroids, comets all revolve around the Sun

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Astronomical Unit

  • One astronomical unit (AU) is the Earth’s average distance from the sun.

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1 AU = 93,000,000 miles = 150,000,000 km

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  • Astronomical units are used to measure distances in our Solar System

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How did the Solar System Form?

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To Scale: The Solar System

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Inner Planets

  • 4 planets closest to the Sun are the inner planets (also known as terrestrial or rocky planets)
    • Small
    • Rocky
    • Dense
    • Have few or no moons

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Mercury

  • Smallest
  • No moon or atmosphere
  • Many craters
  • Extreme temperatures

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Venus

  • Earth’s twin in size
  • Thick clouds
  • Hottest planet! (on average 460o C)
  • A day is longer than a year
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Earth

  • Liquid water on surface
  • In “Goldilocks Zone”
  • Only place with life

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Mars

  • Evidence of liquid water on surface in distant past
  • Largest volcano in Solar System
  • 2 moons

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Asteroid Belt

  • Region between Mars and Jupiter (separates inner from outer planets)
  • Rocky objects too small and numerous to be considered planets
  • Leftover pieces from Solar System formation
  • Over 100,000 identified and still more to find
  • Meteoroids come from asteroids or comets

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Outer Planets

  • Also known as gas giants
    • Mainly of hydrogen and helium (H and He)
    • Thick atmospheres
    • no solid surface
    • many moons
    • ring systems

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Jupiter

  • Most massive planet
  • Dense core of rock and iron
  • 63+ known moons

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Saturn

  • Less dense than water
  • Famous rings!
    • tiny chunks of ice and rock
  • 47+ known moons

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Uranus

  • Blue-green color due to methane
  • Tilted 90o from vertical
  • 27+ known moons

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Neptune

  • Uranus’ twin
  • Fastest winds (1300 mph)
  • 13+ known moons

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Kuiper Belt

  • A belt (like the Asteroid Belt, but bigger and icy) beyond Neptune
    • many comets originate (icy, rocky, dusty objects)
  • Pluto demoted to “dwarf planet” in 2006 -- part of Kuiper Belt
    • 4 other known dwarf planets
      • Eris (bigger than Pluto)
      • Haumea
      • Makemake
      • Ceres (in Asteroid Belt)

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The Oort Cloud

  • “Land of Comets” even farther from the Sun
  • 5000 to 100,000 AU away!
  • Spherical region that surrounds the Solar System

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