Download Chapter 22- Our Solar System - McGann

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Unit 8 Chapter 27 The Planets of the Solar System
Section 1 The Formation of the Planets
Solar System
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Planet
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The Nebular Hypothesis
In 1796, French Mathematician Pierre-Simon, Marquis de LaPalce
advanced the hypothesis that we have called the Nebula
Hypothesis.
Solar Nebular is a rotating cloud of gas and dust from which the sun
and planets were believed to be formed from. The cloud may have
come from either exploding stars or colliding stars and even
material left over from the start of our universe. The cloud starts to
shrink either under its own weight or because a near by star
explodes. Most of the materials move towards the center and
became very hot. Then the cloud starts to shrink and spin,
eventually an eddy (whirlpool) forms. The interior gets hot material compresses together (hydrogen fusion start) - a star (our
sun) is created. Smaller eddies compact into proto planets (or
planetesimals) which later forms planets, moons, comets,
meteorites, asteroids and dust.
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Formation of the Planets
The Proto Planet Hypothesis (was also known as the Nebular Hypothesis)
1944 Von Weizsacker proposed the hypothesis
1950 An American astronomer named Kuiper modified it
A gigantic rotating (spinning) cloud of dust and gas was gradually
transformed into the sun, the planets, their natural satellites and other
bodies to make the solar system. This happened about 4.6 billion years
ago.
Planetesimals are small bodies from which a planet originated from in
the early stages of the development of the solar system.
Dwarf Planets are smaller bodies that gathered mass but not enough
to become a larger body like a planet.
The Formation of the Inner Planets
Four planets that are closer to the sun contained most of the heavy
materials. They then lost most of the lighter gases because the
gravity was not strong enough to hold on to it. They became
smaller, rockier and denser than the outer planets.
The Formation of the Outer Planets
These planets formed further away from they sun, they became
colder, less dense than the rocky inner planets. They kept their
gases and the lighter ices. They came to be known as the “Gas
Giants”.
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Pluto – The First Dwarf Planet
Pluto was discovered in 1930 and was at that time known as the 9th
Planet. Unfortunately it did not follow the characteristics of the outer
planets and in 2006, Pluto lost it’s planet status. It was named a
Dwarf Planet.
The Formation of Solid Earth
When Earth was formed it was hot. The sources of the heat were
from the original collision with space debris, the compression of the
materials forming layers and the decay of radioactive material.
Early Solid Earth
In its early stage, the Earth had only three layers
Core – iron and nickel
Mantle – iron and magnesium
Crust – silica rich material
Present Solid Earth
As it cooled, the lighter materials rose to the surface and formed the
continents. Then the atmosphere underwent drastic changes.
The Formation of Earth’s Atmosphere
Earth’s Early Atmosphere
The early atmosphere was extremely deadly.
It took millions of years
H2O(V) - water vapor
*CO2 - Carbon dioxide
SO2 - Sulfur dioxide
CH4 - Methane
Outgassing
The internal heat caused volcanoes to erupt releasing gases into the
atmosphere. Some of the gases released were carbon dioxide,
nitrogen, methane, sulfur dioxide, ammonia and WATER VAPOR.
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A breakdown started to occur due to solar radiation which caused the
molecules to break apart and then reform other elements. One of
which was Ozone.
Earth’s Present Atmosphere
After this the atmosphere became conducive to growing life. As one
celled plants developed into multiple celled ones, photosynthesis
kicked in. Plants used the carbon for food and released the oxygen
for our life.
The Formation of Earth’s Oceans
Some scientists believe that the early oceans were fresh water
bodies. They feel that some of the water may have come form space
in the form of comets colliding on earth.
Over millions of years, rainwater fell to Earth and ran over the land,
through rivers, and into the ocean. The rainwater dissolved some of
the rocks on land and carried those dissolved solids into the oceans.
As more dissolved solids were carried to the oceans, the
concentration of some of these chemicals combined to form salts.
Over millions of years, water has cycled between the oceans and the
atmosphere making the water concentration more salty.
The Ocean’s Effect on the Atmosphere
The oceans affect global temperatures in a variety of ways. One way
the oceans affect temperature is by dissolving carbon dioxide from
the atmosphere. Scientists think that early oceans also affected
Earth's early climate by dissolving carbon dioxide. Carbon dioxide in
the atmosphere keeps energy from escaping into space and thus
helps to heat the atmosphere.
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Section 2 Models of the Solar System
Early astronomers came up with the idea that everything revolved
around the Earth.
Early Models
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____________________. He thought that the earth is the center of
everything and all things move around it. It explains all facts
including retrograde motion. It is proved to be very complicated. Still
it was used until the 16th century.
RETROGRADE MOTION
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Earth examples:
1. Passing cars just as you pass the car both cars seem to be
moving the same speed
2. Sitting in a car-a car next to you starts to move and you think you
are moving
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__________________________________. This became the basis for
our modern system. It explains all facts even retrograde motion.
Another Astronomer who helped us with our present model was
Galileo Galilei. He was the first person to use a telescope to look at
the stars and planets. He went blind from looking at the sun. He
also discovered moons around Jupiter which supported the
heliocentric law.
Kepler’s Laws
A 16th century Danish Nobleman, _______________ made very
precise measurements of the stars, the planets, and their
movements. He did this without a telescope. He kept a journal and
had many students and assistants who studied his findings.
____________________________ was one of his assistants. He
studied all of Brahe’s notes and developed the “LAWS of Planetary
Motion” which we use to explain all planetary motions.
Law of Ellipses
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ECCENTRICITY
Measures how unlike an ellipse is to a circle.
When the eccentricity is small (close to 0) the two foci
must be closer together or in the same spot. This
makes the shape closer to a circle.
This causes the planets to vary their distances to the sun
at different times during their orbit.
Eccentricity = distance between foci
Length of major axis
0-perfect circle
1-line
Eccentricities of the planets are in the reference table
Because the earth’s orbit isn’t a perfect circle we are closer in
the winter and further away in the summer.
Law of Equal Areas
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Law of Periods
Used to be called the “Harmonic Law of Planetary Motion”
Period2=Distance3
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_______________. The distance is in Astronomical Units (A.U.) or
the distance from the earth to the sun. Earth is approximately 30km
per second.
Newton’s Explanation of Kepler’s Laws
Isaac Newton (1642- 1727)
Came up with the universal Laws of Gravity and Laws of Motion
English scientist and mathematician developed an explanation
for what keeps the planets in motion.
Law of Motion
An object traveling a straight line will stay in motion at the
same speed unless an external force changes something.
Newton’s Model of Orbits
Universal Law of Gravity
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Gravity=Mass (1) Mass (2)
Distance2
It is only strong when at least one mass is
very large and the distances are small.
Tides are the gravitational pull of the moon and the sun
on our water.
The sun pulls the planets out of a straight line into an
orbit around it.
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Escape velocity- the minimum speed needed to escape the earth’s
gravitational pull
-11.2km/sec or 6.9 miles/sec
~25,000miles/hour
Section 3 The Inner Planets
Inner Planets Terrestrial – small – solid land
very dense
Mercury, Venus, Earth, Mars
*Pluto - outer planet w/solid surface; not very dense:
removed from our ESRT in 2006
**See Reference Table for planet notes**
Mercury
It is the nearest planet to the sun
It is the smallest terrestrial planet
It has a magnetic field about 1% of Earth’s
Mariner 10 photographed it in 1974 & 1975
It turns on axis once every 59 days
Hot daytime (400oC) Cold nighttime (-200oC)
Venus
Magellan spacecraft mapped it in 1990
It is sometimes called Earth’s sister; similar diameter, mass & gravity
It has a weak to non-existent magnetic field
It rotates East to West
It’s has thick, pale yellow clouds
In 1985 2 balloons carrying weather instruments found mostly
carbon, 3% nitrogen
It is very hot 475oC
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Earth
We studied it all year.
It is the 3rd rock from the sun.
Mars
It is half Earth’s diameter
It is 2/5’s Earth’s gravity
It is colder; summer 27oC, Winter -125oC
The atmosphere is 95% Carbon, 5% Nitrogen & Argon
It has less than 1% pressure of Earth
We are continually studying this planet now
Section 4 The Outer Planets
Outer Planets - Jovian – large – Gas Giants
less dense
Jupiter, Saturn, Uranus, Neptune
Jupiter
It is the 5th planet in the solar system.
It rotates the fastest of all planets (once every 10 hours)
It is the largest planet (2times the total mass of all planets combined)
It has the strongest known magnetic field
It radiates 2 times as much heat back into space as it receives
It has a great red spot (rotates slower than rest of atmosphere)
On December 7th, 1995 Galileo probe entered the atmosphere
There are at least 63 moons
Saturn
The 6th planet
It turns once every 10 hours
It has rings of gas and dust surrounding it
It has areas of rising and sinking gases that has caused the yellowish
banded color
It has the lowest density (it could float in water)
It has about 60 moons
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Uranus
It was not discovered until 1781
It is 19 times farther from the sun
Its average temp is -200oC
It turns on its axis 17.2 hours
It also has about 12 thin rings around it
It has a sideways rotation which could have been caused by being
knocked by a large object
Voyager 2 flew past it in 1986 and discovered its magnetic field is
about 60% off from the rotation
About 27 moons
Neptune
It was discovered in 1846, after it was mathematically predicted
In 1989 Voyager 2 discovered the magnetic axis is tipped 47%
It has strong winds; 2000km per hour
It has a temperature of -225oC
The atmosphere is hydrogen (74%); helium (25%); methane (1%)
It changes position with Pluto every 248 years and lasts about 20
years
It has about 13 moons
Objects Beyond Neptune
Pluto
Has the smallest everything (smaller than our moon)
It has a diameter is 2,274 km (like from New York to Oklahoma City
is 2140 km)
It has a moon Charon (about 1172 km diameter) along with 2 other
moons
It has a Temp of approximately -235oC to -210oC
Pluto has been since removed from our solar system in 2006 and
called a dwarf planet.
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Kuiper-Belt Objects
The Kuiper belt contains 100’s of objects in a area beyond Neptune’s
orbit. They are called TNO or Transneptune objects. Some are the
size of Pluto and some are smaller chunks of ice.
A few objects named Eris, Makemake, and Haumea are being
considered as dwarf planets
Exoplanets
Exoplanets are planets discovered outside of our solar system. By
studying them hopefully we can learn more about our solar system
and our planets.