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Astronomy
Our Solar System
Chapter 29.1-29.3
Kepler’s First Law

Each planet orbits
Sun in a shape
called an Ellipse

An astronomical unit
(AU), 1.496 × 108 km, is
the average distance
between the Sun and
Earth.
Kepler’s Second Law
-
Planet moves fastest
when closest to Sun
and slowest when
farthest from the Sun
-
Equal areas
are swept out in equal
amount of time.
Kepler’s Third Law

Galileo Galilei
proved, by
discovering four
moons orbiting the
planet Jupiter, that
not all celestial
bodies orbit Earth,
and therefore, Earth
is NOT the center of
the solar system.
The Terrestrial Planets

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Inner four planets of
solar system.
Mercury
Venus
Earth
Mars
Have solid, rocky
surfaces.
Gas Giant Planets


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Outer planets of
solar system
Jupiter
Saturn
Uranus
Neptune
Much larger, more
gaseous, and lack
solid surfaces.
So What About Pluto?
–
Has a solid
surface, but it
does not fit into
either category.

More like a moon
MERCURY
Closest planet to
Sun and has no
moons.
 One-third the size of
Earth.
 Smaller mass and
radius than Earth.

MERCURY

Essentially no
atmosphere, and what
little does exist is
composed primarily of
oxygen and sodium.

Surface is covered with
craters and plains.

Its high density
suggests that it has an
extensive nickel-iron
core, filling about 42%
of Mercury’s volume.
VENUS
Brightest planet in
Earth’s nighttime
sky.
 Surface is very hot,
and rotates slowly
counterclockwise
with one day
equaling 243 Earth
days.

VENUS

Hottest planet in the
solar system with an
average surface
temperature of about
737 K (867°C).

Atmosphere: Primarily
carbon dioxide
and nitrogen with
clouds of
sulfuric acid.
Smoothed by volcanic
lava flows, and it has
only a few impact
craters.
EARTH
Liquid water exists
in all three states:
solid, liquid, gases.
 78% Nitrogen and
21% Oxygen


Precession is the
wobble in Earth’s
rotational axis
MARS

Outermost of the
terrestrial planets.

Less dense than
Earth and has two
irregularly-shaped
moons, Phobos and
Deimos.
MARS
–
Similar to Venus’s
atmosphere, but with
much lower density
and pressure.

Thin atmosphere is
turbulent, which creates
a constant wind
Southern hemisphere is a
heavily cratered, highland
region, while the northern
hemisphere is dominated by
plains.
Gas Giant Planets

Interiors are
composed of fluids,
either gaseous or
liquid, and possibly
small, solid cores.

Have many satellites
as well as ring
systems, and they
are all very large.

Composed primarily
of lightweight
elements such as
hydrogen, helium,
carbon, nitrogen,
and oxygen, and
they are very cold at
their surfaces.
JUPITER

Largest planet,
making up 70% of
all planetary matter
in our solar system

Banded appearance
as a result of flow
patterns in its
atmosphere.
JUPITER
–
–
Hydrogen and helium
make up the majority
of atmospheric gas.
Electric currents flow
within the layer of
liquid metallic
hydrogen and
generate Jupiter’s
magnetic field.
At less than 10 hours,
Jupiter has the shortest day
in the solar system.
Jupiter, like the other three
gas giant planets,
has rings.
SATURN

Second-largest
planet in the solar
system.

Saturn’s atmosphere is
dominated by hydrogen
and helium but it also
includes ammonia ice.
URANUS

Discovered
accidentally in 1781.

At least 18 moons
and 10 rings.

Blue, velvety
appearance
URANUS
–
Internal structure is
completely fluid except
for a small, solid core
and it has a strong
magnetic field.
–
The rotational axis is
tipped over so far that
the north pole almost
lies in its orbital plane.
NEPTUNE
–
Four times as large as
Earth.
–
Neptune and Uranus
include their bluish
color, atmospheric
compositions,
temperatures, magnetic
fields, interiors,
and particle belts.