Download Observing the Solar System

Observing the Solar
System
Ch 14.1
Standards
 8.4.c. Students know how to use astronomical units and
light years as measures of distance between the sun,
stars, and Earth.
 8.4.d. Students know that stars are the source of light
for all bright objects in outer space and that the Moon
and planets shine by reflected sunlight, not by their
own light.
Earth at the Center
 Greek Observations
 “planet comes from
the Greek word
“wanderers”
 In a geocentric
system, Earth is at
the center of the
revolving planets
and stars.
Earth at the Center
 Ptolemy’s Model
 Ptolemy’s geocentric
model was incorrect,
but the motions he
recorded in the sky
were accurate.
 People believed the
geocentric model for
nearly 1500 years
after Ptolemy died.
Sun at the Center
 Some people believed
in the heliocentric
model.
 Heliocentric: Earth
and other planets
revolve around the
sun.
The Copernican Revolution
Copernicus worked out the arrangement of the known
planets and how they move around the sun.
Many people unwilling to accept the geocentric
model.
Sun at the Center
 Galileo’s Evidence
 Galileo used the newly invented telescope
to make discoveries that supported the
heliocentric model.
 He discovered that Venus went through
phases like the moon. He would not see
this if the Earth was at the center.
Motions of the Planets
 Copernicus thought
that the planets
traveled in a percent
circle
Tycho Brahe’s Observation
When he made his observations, he didn’t
even have a telescope!
His student was Johannes Kepler
Motions of the Planets
 Kepler’s First Law
 Kepler used Tycho Brahe’s data to develop the
three laws about the motions of the planets.
 Kepler evnetually found out that Mars’s orbit
was a slightly flattened circle, or an ellipse
(oval shape).
 Kepler’s Second Law
 Speed of planets change as they go around the
sun
 Faster when closer to the sun, slower when
further away
Motions of the Planets
 Kepler’s Third Law
 Planets that are closer to the sun, like
Mercury and Venus, orbit the sun faster
than the ones further away, like Neptune
and Uranus
Modern View of the Solar System
 Components of the Solar System
 Planets vary greatly in size and
appearance
 Moon: natural satellite that revolves
around a planet
 Mercury and Venus don’t have moons
 Solar System consists of the sun, the
planets, and their moons, and several
kinds of smaller objects that revolve
around the sun.
Modern View of the Solar System
 Measuring Distances in the Solar System
 Astronomical unit: the Earth’s average
distance from the sun
 About 150 million kilometers
 On average, Saturn is 9.6 times further
from the sun than Earth.
Modern View of the Solar System
 Exploring the Solar System
 We still use telescopes, like Galileo, but
we can put telescopes in space to get a
closer look
 Sun is the source of all visible light in the
solar system
 Just like the moon reflects the sunlight,
the other planets reflect sunlight.
 Also have launched many space probes to
put on other planets so we can get
samples of what their surface is made out
of.
Names of the Planets!
Roman Name
Greek Name
Their Role
Mercury
Hermes
Messenger God
Venus
Aphrodite
Godess of Love
Mars
Ares
God of War
Jupiter
Zeus
King of Gods
Uranus
Kronos
God of Time
Neptune
Poseidon
God of Seas
Pluto
Hades
God of Underworld & Precious
Metals