Models of the Solar System

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Models of the Solar System
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According to the Greeks Earth was the center of
universe Geocentric Model
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Planet means wonderer for a reason This is
Mars
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Ptolemys epicycle (small circles) explained this
weird motion
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Whats actually occurring
Mars moves slower in its orbit because its
further from the Sun So, Earth overtakes it
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Mars Retrograde Motion
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FinallyCopernicuss Model!
Galileo helped confirm this model a century
later Telescope
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Tycho Brahe
Danish astronomer Best all-time
observationalist Still use his data Hired Kepler
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Keplers Model
Keplers First Law Planetary orbits are
elliptical

• Johannes Kepler
• German astronomer and mathematician
• 1571-1630
• Developed explanations of most planetary motions
  using three laws.
• First law changed the model to included
  elliptical orbits instead of circular

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Orbits are closer to circle than egg
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Keplers 1st Law

• Law of Ellipses
• Ellipse Squashed circle
• Circle is a special ellipse
• Sum of all lines in triangle are equal
• Two foci (circle has both at same point)
• Perihelion
• Aphelion
• Average both to get our distance from Sun
• AU Is the semi-major axis
• (highly exaggerated ?)

Sun at one focus
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Keplers 2nd Law
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2nd Law is the Law of Equal Areas
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Whats an AU again?
P2 a3 Where a is distance in AUs
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Keplers Third Law

• This law explains the orbit of a revolving body
• Orbit time it takes to revolve once around Sun
• Period (p) is proportional to distance

p2
a3

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Enter Newton

• Marble and bowling ball
• Drop or shoot bullet
• Discovered gravity
• Acceleration types
• Acceleration requires force
• Circular motion (planetary) requires a force
• Modified Keplers Third Law
• Added mass to equation
• Can find the masses of revolving objects in space
  with this equation

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Innies vs. Outties or Comparative Planetology
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Do they have ANYTHING in common? Yes!
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Jupiter and its moons(notice rotation and
revolution)
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So, how do they differ???
Just think of the outer planets being almost
everything the inner planets are NOT.
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SIZE!
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Orbits, distances from Sun and their years
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Composition, mass and density
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Periods of Rotation
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Ring Systems