Download 7.4 Meet Your Solar System

7.4 Meet Your Solar System
Homework: Page 296 # 1-3, 6, 7
Learning Goals
• I can differentiate between the geocentric
and heliocentric models of the solar
system.
• I can describe retrograde motion and
explain why it happens.
• I can describe the properties of the inner
planet and the outer planets.
• Two models of the solar system are the
geocentric model and heliocentric model.
• The planets share many similar characteristics,
but they also have many differences.
• The inner, or terrestrial, planets are rocky and
small. The outer planets, or gas giants, are
made of gases and are huge.
• The astronomical unit is defined as the average
distance between Earth and the Sun.
The Planets
• Planet: an object that orbits one or more
stars (and is not a star itself), is spherical,
and does not share its orbit with another
object
• Solar system: a group of planets that circle
one or more stars
Models of the Solar System
• Geocentric model (geo means Earth) 
Earth is the centre of all planetary motion,
with the planets and the Sun travelling it in
perfect circles
• Heliocentric model (helio means Sun) 
Sun is at the centre of the solar system
and has the planets orbiting around it in
perfect circles
The current heliocentric (Sun-centered) model of
the solar system was first introduced in the 1500s by
Polish astronomer Nicolaus Copernicus.
Previous models of the solar system were
geocentric (Earth-centered), originating with the
Greek astronomer Ptolemy.
The Planets
Image above shows relative size correctly, but not relative distance.
Retrograde Motion
• Retrograde motion: the movement of an
object in the sky, usually a planet, from
east to west, rather than in its normal
motion from west to east
• Produced when Earth catches up with and
passes an outer planet in its orbit
Retrograde Motion
Try this flash animation to learn about retrograde motion (best viewed in Firefox):
http://www.mytextbook.ca/product/9780070318618/itr/ppt/assets/OS9.PPT.U3.CH7.slide
35.Retro_Nav.swf.html
Distances between the Planets
• Astronomical unit (AU): the average distance
between Earth and the Sun
– About 150 × 106 km
• Orbital radius: the average distance between
the Sun and an object that is orbiting the Sun
Classifications of the Planets
• Inner planets
– Mercury, Venus, Earth, Mars
– Called the terrestrial (Earth-like) planets
– Relatively small, have solid cores and rocky crusts
• Outer planets
–
–
–
–
Jupiter, Saturn, Uranus, Neptune
Formed from large clumps of gas, ice, and dust
Large gaseous bands and cold temperatures
Called gas giants
Classification of the Planets
Mercury,
Venus, Earth,
and Mars are
called the
inner planets.
These planets
are also called
the terrestrial
(Earth-like)
planets. They
are relatively
small and
have solid
cores and
rocky crusts.
Mercury
Venus
Earth
Mars
Saturn, Jupiter,
Uranus, and
Neptune are
called the outer
planets or the gas
giants. These
planets were
formed from large
clumps of gas,
ice, and dust.
They are also
known for their
large gaseous
bands and cold
temperatures.
Jupiter
Saturn
Uranus
Neptune
Copyright © 2010 McGraw-Hill Ryerson Ltd.
Solar System Data
(Pages 294-5)
Inner Planet Data
Outer Planet Data
Copyright © 2010 McGraw-Hill Ryerson Ltd.
Practice
• Page 296 # 1-3, 6, 7