Transcript Unit 8 Chapter 27 The Planets of the Solar System

Unit 8 Chapter 27 The Planets
of the Solar System
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Section 1 The Formation of the Planets
Solar System
The solar system is the sun, the planets and other
bodies that revolve around an object. (for us it is Mr.
Sun)
Planet
A planet is a primary body that revolves around a sun.
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.
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
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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”.
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
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Core – iron and nickel
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Mantle – iron and magnesium
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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.
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It took millions of years
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H2O(V) - water vapor
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*CO2 - Carbon dioxide
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SO2 - Sulfur dioxide
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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.
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 from 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.
Section 2 Models of the Solar
System
Early astronomers came up with the idea that everything
revolved around the Earth.
Early Models
2000 years ago Greek Philosopher Aristotle suggested a
Geocentric Model. 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
It is the apparent backwards motion of the planets as they move across the
sky nightly.
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
In 1543 Polish scientist Nicolaus Copernicus stated that it is a Sun
centered solar system. 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, Tycho Brahe
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.
• Johannas Kepler 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
All planets move in Elliptical orbits with the sun at
one focus. There must be two foci.
• 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
Equal area law- as a planet revolves around the sun the planet marks
out equal areas in equal time
Law of Periods
Used to be called the “Harmonic Law of Planetary Motion”
Period2=Distance3
The further a planet is from the sun the longer it takes to revolve around it. The
distance is in Astronomical Units (A.U.) or the distance from the earth to the
sun. Earth is approximately 30km per second.
Kepler's 3rd Law
T in years, a in astronomical units; then T2 = a3
Discrepancies are from limited accuracy
Planet
Period T
Dist. a fr. Sun
T2
a3
Mercury
0.241
0.387
0.05808
0.05796
Venus
0.616
0.723
0.37946
0.37793
Earth
1
1
1
1
Mars
1.88
1.524
3.5344
3.5396
Jupiter
11.9
5.203
141.61
140.85
Saturn
29.5
9.539
870.25
867.98
Uranus
84.0
19.191
7056
7068
Neptune
165.0
30.071
27225
27192
Pluto
248.0
39.457
61504
61429
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 is a force that exist between all objects that have mass.
• Gravity=Mass (1) Mass (2)
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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.
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
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 are larger and less dense
Gas Giants
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
Some Scientist feel that it has rings around it too
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
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
Some Scientists feel that it has some rings around it
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.
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.