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The Planets
Terrestrial and Gas planets
 To be considered a planet
 must orbit one or more stars
 its own gravity holds it in a spherical shape
 be the only body occupying the orbital path
Terrestrial and Gas planets
 Large distances keep our solar neighbourhood’s family
of eight planets well separated from each other
 Astronomical unit (AU), is equal to the average
distance between the Sun and Earth, about 150 million
km.
 Earth is 1 AU from the Sun, while Jupiter is 5.27 AUs
from the Sun.
Terrestrial planets
 Four inner Planets
 Have rocky surfaces
Terrestrial planets
 Mercury
 The closest planet to the Sun is also the smallest.
 slightly larger than our Moon
 differences between night and daytemperatures on its
surface (ranging from 400°C to –183°C).
Terrestrial planets
 Venus
 often called Earth’s sister planet
 similar size and composition to Earth
 Venus’s atmosphere is almost
completely carbon dioxide
 the Magellan spacecraft revealed that
large portions of the planet arevery
flat, while other areas have volcanoes,
lava flows, and cracks called rifts.
Terrestrial planets
 Earth
 little blue planet, third from the
Sun
 only life yet discovered
 only place known to have water in
three phases
 Water covers nearly three quarters
of Earth’s surface
 Atmosphere of nitrogen and
oxygen
Terrestrial planets
 Mars
 called the red planet
 half the size of Earth
 Mars has a very thin atmosphere
of carbon
 dioxide and can experience
winds of more than 900 km/h.
 Mars has two polar ice caps made
of frozen carbon dioxide
Outer Planets
 Called Jovian Planets
 Much Larger than the Inner Planets
 Have no real surface
Outer Planets
 Jupiter
 largest planet in the solar system
 It has a mass 2.5 times greater than
that of all the other planets
combined
 “Great Red Spot” a storm raging in
the clouds of hydrogen and helium
that form the planet’s outer layers ,as
large as three Earths
 the shortest day (10 hours)
Outer Planets
 Saturn
 elaborate system of
rings (from ice
particles)
 composed mainly of
hydrogen and some
helium
Outer Planets
 Uranus
 fourth most massive planet
 Similar composition to Jupiter
and Saturn, including a ring
system
 blue colour from the methane
gas in its atmosphere
 unusual rotation in that it is
flipped on its side
Outer Planets
 Neptune
 outermost planet
 third most massive
 composition is similar to that of
Uranus, and it has the same dark
blue colour
 Has a ring system
 Some times has a large, blue,
Earth-size patch on Neptune’s
surface likely a storm in the
clouds
Terrestrial and Gas planets
Questions
 Page 411 #2,9,11