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The Solar System:
The Sun & the Planets
Measuring Distances in the Solar System
• The astronomical unit (AU) is used to measure distances
within the Solar System
• The average distance from the Sun to Earth is approx. 150
000 000 km
1 AU = 150 000 000 (1.5 x 108) km
Planets Big & Small
• The Sun is the largest object in the Solar System, the next
largest are the planets.
The Inner Planets = Terrestrial Planets
• Mercury, Venus, Earth & Mars
• Small, rocky planets
• Located between the Sun and Asteroid Belt
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Mercury
Location – Inner
Orbital Period – 88 days
Rotation – 59 days
Atmosphere – None
Temperature – -180 to 400 0C
# of Moons – 0
Rings – 0
Unique Characteristics
• No atmosphere to trap heat
• Contains craters
• Rarely visible in our night sky because it is so close to the
Sun
Venus
• Location – Inner
• Orbital Period – 224.7 days
• Rotation – 243 days
(opposite direction)
• Atmosphere – carbon dioxide,
nitrogen
• Temperature – 462 0C
• # of Moons – 0
• Rings – 0
Unique Characteristics
• Brightest object in the sky after the Sun & Moon
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Earth
Location – Inner
Orbital Period – 365.26 days
Rotation – 24 h
Atmosphere – Nitrogen, Oxygen
Temperature – -88 to 58 0C
# of Moons – 1
Rings – 0
Unique Characteristics
• Ozone – filters some of damaging radiation from the Sun
• Temperatures are constant
• 70% of planet’s surface is water
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Mars
Location – Inner
Orbital Period – 687 days
Rotation – 24.65 h
Atmosphere – Carbon dioxide,
Nitrogen
• Temperature – -90 to -5 oC
• # of Moons – 2
• Rings – 0
Unique Characteristics
• Called the ‘red planet’ due to its rusty soil
• Very dry
• Once had volcanoes, glaciers & water
The Outer Planets = Gas Giants
• Jupiter, Saturn, Uranus & Neptune
• Large, composed of gas
• Atmospheres consist mainly of the gases hydrogen and
helium
Jupiter
 Location – Outer
 Orbital Period – 11.9 years
 Rotation – 9.85 h
 Atmosphere
– Hydrogen, helium, methane
 Temperature – -148 oC
 # of Moons – 63
 Rings – Yes
Unique Characteristics
 Largest planet (11x the diameter of Earth)
 Features are its coloured bands, the Great Red Spot &
hurricanes
 Orbiting rings of rocks
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Saturn
Location – Outer
Orbital Period – 29.5 years
Rotation – 10.65 h
Atmosphere – Hydrogen,
helium, methane
• Temperature – -178 oC
• # of Moons – 60
• Rings – Yes
Unique Characteristics
 Second largest , no solid core
 Cloudy & windy, over 1000 separate rings
Uranus
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Location – Outer
Orbital Period – 84.1 years
Rotation – 17.3 h (on it’s side)
Atmosphere – Hydrogen,
helium, methane
 Temperature – -216 0C
 # of Moons – 27
 Rings – Yes
Unique Characteristics
 Winds blow up to 500 km/h
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Neptune
Location – Outer
Orbital Period – 164.8 years
Rotation – 15.7 h
Atmosphere – Hydrogen,
helium, methane
• Temperature – -214 0C
• # of Moons – 13
• Rings – Yes
Unique Characteristics
 Uneven orbit, Bright blue & white clouds
 Has a dark region called the Great Dark Spot, which
appears to be the center of a storm
Planet Rotations
To be considered a “planet” a celestial object must;
1. Be in orbit around a star (such as the Sun)
2. Have enough mass to be pulled into a stable sphere
shape by gravity
3. Dominate its orbit (i.e., its mass must be greater
than anything else that crosses its orbit)
Dwarf Planets
• A celestial object that orbits the Sun and has a spherical
shape but does not dominate its orbit.
• Ceres, Pluto, Haumea, Makemake, and Eris
• Pluto’s tilted orbit crosses Neptune’s orbit
Planet Locations
Smaller Members of the Solar System
Asteroids
• are composed of rock & metal.
• Although they orbit the Sun, they are too small to be
considered planets.
• Most asteroids lie in the asteroid belt, located between
Mars & Jupiter.
ASTEROID BELT
700,000 to 1.7
million asteroids
with a diameter of 1
km or more.
Over 200 asteroids
are known to be
larger than 100 km.
• A meteoroid is a piece of metal or rock that is
smaller than an asteroid.
• Sometimes they get pulled in
by Earth’s gravity. They burn
up in the Earth’s atmosphere,
creating a bright streak of
light across the sky, known as
a meteor (shooting star).
• Larger meteors do not burn up completely in the
atmosphere and their remains, which we call
meteorites, crash to the ground.
DID YOU
KNOW?
A leading theory on the
extinction of dinosaurs
suggests that a 10 km
wide meteorite impact is
what caused the
extinction of these
animals 65 million years
ago.
Wolfe Creek Crater in Australia
Comets
• Comets are large chunks of ice, dust, and rock that orbit
the Sun.
• As a comet approaches the Sun, radiation and solar wind
from the Sun, causes a gaseous tail to form, pointing
directly away from the Sun.
• A dust tail forms in the
direction from which the
comet originated.
• Most comets have 2 tails;
• gaseous tail
• dust tail
Comets
Homework
WS
P.317 #5, 6, 8