The Inner and Outer Planets

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The Inner and Outer Planets

• A solar story

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Astronomical Unit

• 1 AU 149,597,870.691 kilometers
• (93,000,000 miles)
• Definition An Astronomical Unit is
  approximately the mean distance between the Earth
  and the Sun.
• Why is it the mean distance?
• Answer Because orbits are elliptical
• Jupiter is 5.2 AUs away from the sun

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Mercury

• Smallest terrestrial planet closest to the sun
• No moons
• Surface consists of flat plains and craters
• Very little atmosphere
• Greatest temp. difference 860 F to 274F

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Venus

• Similar to Earth in Size
• Takes 8 months to rotate on its axis and 7.5
  months to revolve around the sun.
• Planet rotates from east to west.

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Earth

• Unique because it has liquid water (70)
• Has enough gravity to hold an atmosphere
• Atmosphere is made out of nitrogen, oxygen and
  carbon dioxide.
• Has one moon

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Mars

• Red because of the iron rich rocks on the surface
• Atmosphere is more than 95 CO2
• Surface temps. range from 140 to 20 C.
• There may have been flowing water
• Has seasons because of its tilted axis
• Has two moons

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The Outer Planets

• Known as the gas planets
• All the gas planets have rings
• Rings are mostly ice but are also composed of
  rock and dust

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Jupiter

• Largest most massive planet
• Thick atmosphere of H and He
• Great red spot the size of Earth
• Prob. has a dense core of rock
• Atmospheric pressure at the core is 30 million X
  that of Earth.
• Many moons most famous are the Galileon moons (4)

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Saturn

• Thick atmosphere of H and He
• The density of Saturn is less than water!
• Rings made of chunks of rock and ice.
• Saturns largest moon is titian

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Uranus

• Blue green color because atmosphere is made up of
  methane
• Discovered in 1781 by William Herschel
• Axis is tilted at 90 deg. and rotates in about 17
  hours
• Has at least 27 moons

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Neptune

• Cold blue planet
• Discovered by mathematical prediction based on
  the orbit of Uranus
• Dark spots are prob. storms on the surface
• 13 moons
• Internal heat source. Slowly shrinking

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Pluto?(The roman god of the underworld)

• Three moons
• Revolves around the sun 1x every 248 Earth years
• Not considered a planet today

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So why isnt Pluto a planet?

• Is Pluto a planet? Does it qualify? For an object
  to be a planet, it needs to meet these three
  requirements defined by the IAU
• It needs to be in orbit around the Sun Yes, so
  maybe Pluto is a planet.
• It needs to have enough gravity to pull itself
  into a spherical shape Plutocheck
• It needs to have cleared the neighborhood of
  its orbit Uh oh. Heres the rule breaker.
  According to this, Pluto is not a planet.
• What does cleared its neighborhood mean? As
  planets form, they become the dominant
  gravitational body in their orbit in the Solar
  System. As they interact with other, smaller
  objects, they either consume them, or sling them
  away with their gravity. Pluto is only 0.07 times
  the mass of the other objects in its orbit. The
  Earth, in comparison, has 1.7 million times the
  mass of the other objects in its orbit.
• Any object that doesnt meet this 3rd criteria is
  considered a dwarf planet. And so, Pluto is a
  dwarf planet. There are still many objects with
  similar size and mass to Pluto jostling around in
  its orbit. And until Pluto crashes into many of
  them and gains mass, it will remain a dwarf
  planet. Eris suffers from the same problem.

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Size comparison of planets
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The next slide shows The Relative Sizes of the
Largest Solar System Objects - in the following
order (to scale) Jupiter, Saturn, Uranus,
Neptune, Earth, Venus, Mars, Ganymede, Titan,
Mercury, Callisto, Io, the Moon, Europa, Triton,
Eris, Pluto
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Size comparison of planets
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Size comparison of planets compared to the Sun
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100 Largest objects in the solar system