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Name______________________________ Teacher___________Period_______Date_________
The Outer Planets (Gas Giants) & Pluto (not a planet)
Place a checkmark in the box if the outer planet matches that characteristic. You may
have more than 1 checkmark for each characteristic.
Jupiter
Saturn
Uranus
Neptune
Atmosphere is mainly
hydrogen & helium
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Contains clouds and/or storms
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Contains methane in its
atmosphere making it appear
blue
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Diameter is 11 times Earth’s
diameter
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Does not have a solid surface
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Four large moons are named
Tethys, Iapetus, Dione & Rhea
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Four times the diameter of
Earth
Galileo probe explored here
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Has a deep atmosphere
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Has a partly solid core of rock,
ice and frozen CO2
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Has or had a spot on it that
behaves like Earth’s
hurricanes
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Has rings
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Its moons have lava flows
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Largest moon is named Titan
Largest moon is Triton
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Largest planet in the solar
system
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Less dense than water, so it
could float in water
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Rotates from top to bottom
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Second largest planet in the
solar system
The four biggest moons are
named Io, Europa, Ganymede
& Callisto
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Twice as far from the sun as
Saturn
Voyager 1 probe explored here
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Voyager 2 probe explored here
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Pluto
Since our book was published, some exciting discoveries have been made in the region that lies
outside of the orbit of Neptune. The region is called the Kuiper Belt and is the home to many
dwarf planets, including Pluto and Eris, which was only discovered in 2005. Eris is bigger than
Pluto! In 2006, the International Astronomical Union met to define what a planet is, and
because Pluto did not fit the 3 criteria, it was deemed a dwarf planet.
The three criteria of the IAU for a full-sized planet are:
1. It is in orbit around the Sun.
2. It has sufficient mass to assume a nearly round shape.
3. It has "cleared the neighborhood" around its orbit.
Pluto meets only two of these criteria, losing out on the third. In all the billions of years it has
lived there, it has not managed to clear its neighborhood. This means that the planet has become
gravitationally dominant -- there are no other bodies of comparable size other than its own
satellites or those otherwise under its gravitational influence, in its vicinity in space.
Don’t ask your teacher if Pluto is a planet! Pluto has not been a “planet” since you have been in
school.