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Planet Motion
Chapter 8, Section
1
Models of the Solar System
• The Ancient Greeks believed in the
geocentric model.
• In the geocentric model, the Earth was at
the center of the universe and that the
stars consist of two spheres
• In the geocentric model, the solar
system would have been arranged
in the following order:
A map of the Geocentric
model
Copernicus
• In 1543, Copernicus came up
with the heliocentric model
• Stated that the moon revolved
around the Earth and all of the
planets revolved around the sun.
• His model could not accurately
predict the location of the
planets and was not widely
accepted
Galileo
• He invented the modern telescope
and was the first person to
document sunspots.
• Found that Venus has phases
much like our moon
• Found that Jupiter has moons
that revolve around it.
• This evidence further supported
the heliocentric model.
• Was forced by the church to recant
all his findings 6/22/1623
Kepler
• In the early 1600s, a
German mathematician
Johannes Kepler took
the work of other
astronomers and put it
together.
• Found that the paths of
planets were ellipses
• Planets travel at
different speeds.
Kepler also learned that the speed of each of the
planets was different and the outer planets took
much longer to orbit the Sun (Mercury=88 days,
Saturn= 29.5 years).
• In the heliocentric model, the solar
system is arranged in the following
order:
Scientists now use two units to measure
distance in space:
– the astronomical unit (AU) which is
equal to the average distance
between the Earth and the Sun
– the light year which is the distance
traveled by light in space in one year.
(L.Y. = 9.5 Trillion km)
Understanding the Solar System
• By definition, there are eight planets which
consist of four terrestrial planets which are
closer to the Sun and four gaseous giant
planets which are further away. The
terrestrial and gas planets are separated
by a belt of rocky debris known as the
asteroid belt.
• Beyond the orbit of the gas giants are no
less than 100 small planet-like objects
known as planetoids (including Pluto).
• The solar system also contains a sizable
collection of meteors, comets, and belts of
rocky materials that also orbit the Sun.
• The solar system is thought to have formed
from a condensing cloud of gas and dust
known as a nebula. As the cloud
contracted, it became super-heated and
created our Sun. The remaining dust and
gasses condensed into the planets.
Other Solar systems
• So far, over 300 stars have been found to
have planetary systems.
• Upsilon Andromedae is one star with
planets around it.
The Inner
Planets
Chapter 8, Section
2
Planets near the Sun
(Inner Planets)
The solar wind
and heat have all
but stripped most
of the gases and
lighter elements
off of the
terrestrial planets.
(Planet size ratio is not accurate)
Mercury
• Smallest of the planets; size of our moon
• Has no atmosphere
• Surface temperatures vary from
-170°C to 427°C
Mercury
• Taken by
Mariner 10
• Mercury in color
Mercury view from sun
Venus
• Size and mass similar to Earth
• Surface pressure is 92x greater than Earth
• Atmosphere is almost entirely CO2
• Surface temperatures vary from 450°C to
475°C
• RETROGRADE ROTATION: Backwards
rotation of a planet
Venus
• As seen
from
Earth
Venus
• As pictured
by
Magellan
spacecraft
• It takes 223 days for Venus to
revolve.
• Rotation takes 243 days! Notice
something????
• Thousands of volcanoes
• Silicon and Oxygen in crust
The Surface of Venus
Radar Images of Surface
Venus in front of the sun
Earth
Earth
• Allows water to exist as a solid, liquid, and
a gas
• Atmosphere burns up most meteors before
they hit the ground
• Ozone in the atmosphere protects the life
from U.V. rays
• Temp. range: -88°C to 58°C
Mars
• Known as the red planet due to the high level of iron
oxide (rust)
• Has polar ice caps
• Appears to have once had flowing water on its surface
• Mars is tilted 25° on its axis and has seasons
• Atmosphere is mostly CO2 and does not filter out harmful
rays
• Surface temperatures vary from -123°C to 37°C
• Mars has two small moons: Deimos and Phobos
• ½ size of Earth!
Mars
NASA on Mars
• NASA sent probes to Mars in the 1970s and
80s but much more detailed information has
come from the Mars Rovers: Spirit and
Opportunity
• In 1996, structures identical in nature to
some bacteria were found fossilized in a
fragment of rock from Mars.
Mars Rover
A Face on Mars?
How Disappointing!
Evidence of Water?
Sunset on Mars
Olympus Mons: Largest Volcano
in Solar System
• Three times taller
than Mt. Everest
• 342 miles across
What do the inner planets have in
common?
• Small
•Terrestrial
• Contain iron cores
• Crust contains heavier elements
• Few or no moons
The Outer
Planets
Chapter 8, Section
3
The Outer Planets
• Why are the outer
planets so different?
• The outer planets
have large amounts
of lighter elements
such as H and He.
• Are not as affected
by the solar wind
than the inner planets
Jupiter
• Is the largest planet
• Composed of hydrogen and helium
SIMILAR TO THE SUN!
• As you get closer to the surface, the
pressure is equal to 50 million Earth
atmospheres and the temperature is apx.
20,000°C
• Thin rings
• Has continuous storms that cause swirls in the
atmosphere
• Has more than 60 moons, of which Io, Europa,
Ganymede, and Callisto are thought to have water
and conditions possible for life to occur
Jupiter
Jupiter
with moons
Comet that struck surface in ‘94
Eclipses on Jupiter
Aurora on Jupiter
Saturn
• Saturn is the second largest planet;
HYDROGEN AND HELIUM!
• Has rings made of chunks of rocks and ice
• Has 53 moons
• The largest is Titan
Saturn
Saturn Edge View
Saturn Surface
Saturn Aurora
Uranus
• Axis is tilted on its side (north to south)
• Has a blue/green color due to its methane
atmosphere
• Has 27 moons
Uranus
Uranus
with rings
Infrared Image of Uranus
Neptune
• Was actually predicted by mathematical
calculations before it was ever seen (It was known
that an object was affecting Uranus’ orbit)
• Has blue color due to methane in its atmosphere
• Has 13 moons
• The largest is Triton
– Has poles covered in ice
– Has eruptions
Neptune
The Great Dark Spot
What do the outer
planets have in common?
• Large and gaseous
• Have rings
• H and He make up atmospheres
• Many moons
• Iron cores
Planetoids (Pluto)
• Is smaller than the Earth’s moon
• Has its own moon, Charon
• Another planetoid is Sedna
Pluto and Charon
Comets and other objects
• Comet – dust, ice, frozen water, methane,
and ammonia, ROCK!!!
• Asteroids – chunks of rocks (>10 meters)
• Meteoroids – chunks of rocks that can
pass through the Earth’s orbit and into the
atmosphere of the Earth; SOME OF
THESE ARE LEFT BEHIND BY COMETS
• (<10 meters)
Comet
Hale~Bopp Comet
Asteroid
Another Asteroid
• Asteroid
belt
between
Mars and
Jupiter
Meteor vs. Meteoroid. vs. Meteorite
• METEROID: a rock that travels aimlessly in
space
• METEOR: a streak of light we see when a
rock is burning up in the atmosphere
• METEORITE: if the rock makes it to the
ground, it’s now a meteorite.
Meteoroid
Meteors: known as shooting stars!
Meteor Shower: Leonid
Meteorite!
When Meteors Attack
Chapter 8,
Section 4
Is There Life
Beyond Earth
Life on other worlds?
• All living things contain CARBON on Earth
• Most life forms on Earth need water and a
comfortable temperature…….but……
• Life has been found to exist in places with
extreme living conditions on Earth
• These extreme living conditions include scalding
hot areas, freezing cold areas, completely dark
areas, etc.
Life on Europa, Jupiter’s Moon
• The surface is covered in large moving
chunks of ice that are possibly made of
frozen water.
Europa, Getting Closer…
Close up of Europa
Titan, Saturn’s Moon
• Nitrogen
atmosphere….don’t plants
on Earth use nitrogen?
• Contains
hydrocarbons…isn’t life on
Earth based on carbon?
• Surface pics show old
riverbeds of ethane….and
liquid METHANE!!! These
are hydrocarbons.
Titan’s Surface from Sky…
yes, it’s real
Titan’s
surface