Download Origins of our Solar System

Origins and Our Solar System
The Solar System
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The 8 planets form 2 different families.
The four closest to the Sun represent
the terrestrial planets – Mercury, Venus,
Earth and Mars.
The four farthest from the Sun are
sometimes referred to as the gas
giants, the Outer Planets, the Jovian
planets – Jupiter, Saturn, Uranus,
Neptune.
The Families Differ
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The families differ in the compositions
of their cores and atmospheres.
Terrestrial planets have ____________
Surrounding the inner ______ core is a
outer core of silicates (rocks)
Range in a diameter of 4880 km –
12800 km
The Outer Planets
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Enormous when compared to the
Terrestrial planets.
Jupiter is the largest with diameter of
143,000 km, Saturn 121,000 km,
Uranus 51,000 km, Neptune 49,500 km
The Outer planets also have cores
composed of Ni and Fe, but the vast
majority of their enormous mass is
from Hydrogen or hydrogen compounds
such as Methane.
The Outer Planets
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Because of their HUGE masses the
gravitational pull is very great.
Due to the low temperature and
pressure these compounds are in
liquid form.
Besides hydrocarbons the most
common element is Helium other
elements such as N, and S are also
present.
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Even though there is such great
variation between the planets the
elements that we find on all the
celestial bodies are similar.
The commonality of elements that
are found on all the planets, moons,
asteroids and celestial bodies leads
us to ask the question: “How did
they all get here?”
Theories Regarding the Origin of the
Solar System
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Catastrophe Theories –
(also called the
planetesimal hypothesis or condensation
theory) – Before the Sun and planets were
formed, the material that became the Solar
system was part of a large diffuse cloud of
interstellar gas and dust comprised of H and
He. The nebula became unstable and started
to collapse in on itself because of gravity.
Origins of the Solar System – Solar
Nebula Theory (cont.)
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The center of the Nebula became the Sun as
Temperature and pressure increased and
thermonuclear reactions began.
As the Sun rotated and the presence of a weak
magnetic field, the nebula began to flatten to
form a disc with the Sun in the center.
As Temperatures decreased material cooled and
condensed from a gas to a solid.
Due to the high temperature closer to the Sun
different elements solidified. This caused the
differing amounts of Fe and Ni in the cores of
the Terrestrial planets and the Jovian planets.
Origins of the Solar System – Solar
Nebula Theory (cont.)
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The grains of elements collided with each
other and formed larger and larger pieces.
were formed – small moon
sized planets that then formed the terrestrial
planets.
(small planets that coalesced
into the Jovian planets) were formed in the
outer solar system because temperatures were
much colder and allowed gases like He and H
to solidify and become parts of the larger
Jovian planets.
Some Evidence Supporting the Nebula
Theory
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Components of the Solar System
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– A star composed of 71%
Hydrogen and 21% Helium. Contains
small amounts of every other element in
vaporous form.
Ball of H and He that generates light
because of nuclear reactions in the core
Largest body in the Solar System 700x
the mass of everything else combined.
More about Stars later
The Terrestrial Planets
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We will discuss the different planets in the
future chapters.
Basic information regarding the two
families:
Terrestrial = Composed of rock
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Rock – Silicates, which have a mix of Oxygen
and Silicon as well as other heavier elements.
Distinct solid “ground”
If there is an atmosphere, it is gaseous.
Terrestrial planets
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The Outer Planets - Jovian
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Jovian Planets = composed of ice
Ice – frozen liquids and gases.
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Examples: water, Carbon Dioxide, ammonia,
and methane
All have a ring system
No distinct boundary between crust and
atmosphere.
As you go deeper into the planet the
gases become more dense, may turn into
liquids, and possibly a solid core.
The transition is not sharply defined
The Jovian Planets
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Satellites
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Every planet in the solar system EXCEPT Mercury
and Venus has at least one satellite (moons).
As we send more probes to the outer planets,
more moons (satellites) have been discovered
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Planets
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Jupiter
Saturn
Uranus
Neptune
Mars
Earth
Pluto
# of Moons
39
30
21
8
2
1
1
Answer the questions in your notes. I
will come around to check
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What is the relationship between
planetary size and the number of
moons?
Can you hypothesize why Venus
does not have any moons? Please
provide 2.
Asteroids
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– Rocky or metallic bodies
ranging in size from a few meters to
1,000km in diameter.
Most asteroids are located in the asteroid
belt located between Mars and Jupiter.
The asteroid belt circles the Sun and is most
likely materials that would have coalesced
into a planet, but Jupiter’s gravity prevented
it from occurring.
Comets
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Comets – Icy bodies about 10 km in diameter.
A tail of gas and dust extends off the comet
as it vaporizes when it nears the Sun.
Most comets are located far beyond the object
once known as Pluto in an area called the Oort
Cloud, which is a spherical region 40,000100,000 AU from the Sun.
If a comet doesn’t originate in the Oort Cloud
it probably came from the Kuiper Belt. Which
is a disk shaped area beyond Neptune. Pluto
and its satellite are most likely Kuiper belt
objects that “escaped” the belt.
Bode’s Law
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A numerical expression for approximate
distances of most of the planets from
the Sun.
Yet to be explained, each planet is
(VERY ROUGHLY) about twice as far
from the Sun as its inner neighbor.
We are unsure if this is just a major
coincidence or a physical property
affecting Solar system formation.
Odds and ends of the chapter
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Age of the solar system: 4.5 billion years old.
The outer planets’ composition is similar to
the Sun.
The inner planets lack some gases that only
form solids at VERY low temperatures (this
does not include the atmospheres of the
planets)
The solar system developed from the solar
nebula- the rotating disk of gas and dust from
which the Sun and planets formed. (imagine a
spinning pizza crust).
Odds and ends of the chapter
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Condensation – when a gas cools
enough to form a solid or a liquid.
There are various theories regarding
when and how the different moons
were formed
Other planetary systems
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There are other stars with planets orbiting
them.
Planets orbiting another star are called
extra-solar planets.
Difficult to see because they are small
and any light they reflect is often
“drowned out” by the light of their sun.
Figure 7.12 lists some of the known
extra-solar planets.