THE SOLAR SYSTEM
The Solar System


Our Sun and everything that orbits it.
Contains:
 The
Sun
 Eight planets
 Many dwarf planets
 An asteroid belt
 Comets
Birth of the Solar System
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Created in a nebula around 4.6 billion years ago.
Dust and gas contracted because of gravity.
As the Sun was forming, the ring of dust around it
was spinning very fast. Smaller clumps of dust
contracted into planets and other smaller bodies.
The Sun
A small yellow
star made mostly
of hydrogen and
helium.
 Temperature:
 Surface Temp:
~5800K
 Core Temp:
~15,700,000K

The Planets

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Planet – A large astronomical body that orbits a
star.
To be a planet, it must:
 Be big enough to be rounded by its own gravity.
 Be small enough to not undergo nuclear fusion.
 Have cleared its neighborhood of other planets
There are eight planets: Mercury, Venus, Earth,
Mars, Jupiter, Saturn, Uranus, Neptune.
Planetary Motions - Rotation
Rotation – The motion of a planet spinning
around its axis.
 Rotation determines how
long a day is.
 The Earth’s period of rotation
is 24 hours.


What do you think rotates faster,
a small planet or a large planet?
Planetary Motions - Rotation

A large planet!
Jupiter has the fastest rotation out of any planet.
 1 rotation of Jupiter is equal
to just under 10 hours.

Proof of Rotation

Foucault’s Pendulum
Coriolis Effect
Day/night cycle
Constellation motions over one night

Anything that happens over ONE DAY.
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Foucault’s Pendulum

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An experiment done that demonstrates the rotation
of the Earth.
https://www.youtube.com/watch?v=XJc1dnbVK_0
Coriolis Effect

Wind will curve due to the rotation of the Earth.

Example of Coriolis Effect

Explanation
Day/Night Cycle

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Day and night happen because of the Earth’s
rotation.
The part of the Earth that is facing the Sun will
experience day time.
When that part rotates away from the Sun, it will
be night time.
Star Motions

Stars appear to move throughout the sky over one
night because of rotation.

If the Earth rotates 15˚ per hour, and each star trail
is 30˚ wide, how many hours have passed in this
picture?
Planetary Motions - Revolution


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Revolution – The motion of a planet around a star.
Period of revolution determines how long a planet’s
year is.
Earth’s period of revolution is 365 days.
Proof of Revolution

Seasons
Constellations travelling around the sky

Changes that happen over the course of ONE YEAR

Constellations
Types of Planets

We classify planets in two ways:
 Terrestrial
Planets
 Jovian Planets
Terrestrial Planets
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Mercury, Venus, Earth, Mars (first four)
Closer to the Sun
Shorter revolution
Smaller
Dense
Rocky
Few to no moons
No rings
Jovian Planets

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Jupiter, Saturn, Uranus, Neptune (last four)
Farther from the Sun
Longer Revolution
Bigger
Less dense
Made of gas
Many moons
Have rings
Other Solar System Objects

Moons
 Also
called satellites
 Large bodies that orbit a planet.
Terrestrial planets have few or no moons.
 Earth has 1
Jovian planets have many moons.
 Saturn has 62
Earth’s Moon

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Formed when a huge object hit Earth while it was
cooling.
Parts of the Earth broke off and condensed into the
Moon over time.
Saturn’s Moons
Asteroids

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Asteroids – Irregularly shaped chunks of rock in
space.
Not big enough to be planets or moons.
Huge belt of asteroids between Mars and Jupiter.
Meteoroids
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Meteoroids – Small rocky or metal objects that
travel in outer space.
They can enter Earth’s atmosphere and become
meteors. Most burn up in the atmosphere.
If it survives passing through the atmosphere, it ends
up as a meteorite.
Comets
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Comet – A ball of ice and rock with a tail.
They have a very long period of revolution, with
long elliptical orbits.
“Dirty Snowballs”
Dwarf Planets
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Large bodies that are similar to planets, but have
not cleared their neighborhood of other bodies.
Examples – Pluto, Ceres, Eris
History of Astronomy
Early Astronomy
The
“Golden Age” of
astronomy was
centered in Greece.
Early Astronomy ~350 B.C.

The Greeks took measurements
of distant objects such as the
Sun and the moon.

Aristotle concluded that the
Earth is round because it always
cast a curved shadow on the
moon.

Hipparchus determined the
location of almost 850 stars.
Aristotle (384-322 B.C.)
Hipparchus (190-120 B.C.)
Geocentric Model

The Greeks believed in a geocentric
universe, in which the planets and
the Sun revolved around the Earth.
Geo = Earth
 Centric = Centered
 Couldn’t account for strange
motion of planets called
“retrograde motion”.

Geocentric Universe

The idea that the Earth is at the
center of the universe and all
things fall around it is the simplest
and longest lasting universal view
that we have had.

IT’S ALSO WRONG.
Assumptions about the
Geocentric model
1. The Earth is the center of all motion.
 2. The Earth does not move.
 3. The Earth is flat.
 4. Planets move in circular orbit.

We know today that these are NOT
TRUE
Retrograde motion

Retrograde motion – The motion of a planet that
makes it appear to move backwards compared to
other objects in the sky.
Retrograde Motion
Ptolemaic System ~130 A.D

The Greek astronomer, Ptolemy,
thought of a geocentric model of
the universe called the Ptolemaic
System, with fixed stars in the
background.
 Ptolemy
tried to explain retrograde
motion through epicycles.
Ptolemy (90-168 A.D.)
Heliocentric Model
Aristarchus (~230 B.C)
suggested a heliocentric
universe, with the Earth and
other planets revolving around
the Sun.
 Helio = Sun
 The heliocentric model was
unpopular when it was
introduced.

Aristarchus (312-230 B.C.)
Assumptions about the
Heliocentric model
1. The Sun is the center of all motion in our
solar system.
 2. The Earth moves around the Sun.
 3. The Earth is spherical.
 4. Planets move in an elliptical orbit.

We know today that these ARE TRUE!
Heliocentric Model
The Birth of Modern Astronomy
(1500s)

After Ptolemy, very few advances
were made in astronomy.

The first great astronomer to
emerge after the Middle Ages was
a man from Poland named
Nicolaus Copernicus.

He believed the Earth was a planet,
just like the other 5 known at the
time, and supported the
heliocentric model of the universe.
Copernicus (1473-1543)
Father of Modern Astronomy
The Birth of Modern Astronomy
In the 1600s, Tyco Brahe and
Johannes Kepler gathered very
precise data and observations.
 Kepler discovered laws about
how planets move around the
Sun. One law is that they
revolve around the Sun in an
oval called an “ellipse”.

Kepler (1571-1630)
The Birth of Modern Astronomy
(1600s)

Galileo Galilei was a great
Italian scientist during the
Renaissance.
 Everything
before Galileo was
studied without a telescope.
 He
constructed his own telescope
and used it to study the sky, making
many important discoveries
supporting Copernicus’s view of the
universe.
Galileo (1564-1642)
The Birth of Modern Astronomy
(1600s)
With Galileo’s evidence added to Brahe’s
and Kepler’s data and Copernicus’
model, the heliocentric model was finally
starting to become accepted.
 The church did not accept it at first and
labeled Galileo as a heretic, but
eventually accepted the heliocentric
model by the 1660’s.

th
20
century Astronomy
In 1957, the
Russians launched
Sputnik, the first
artificial satellite.
 Caused the “Space
Race”

Man on the Moon

In 1969, the US
became the first
nation to send a
manned crew to
the Moon.