Origins and Our Solar System

1
Origins and Our Solar System
2
The Solar System

• 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.

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The Families Differ

• 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

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The Outer Planets

• 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.

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The Outer Planets

• 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?

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Theories Regarding the Origin of the Solar System

• 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.

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Origins of the Solar System Solar Nebula Theory
(cont.)

• 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.

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Origins of the Solar System Solar Nebula Theory
(cont.)

• 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.

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Some Evidence Supporting the Nebula Theory

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Components of the Solar System

• 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

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The Terrestrial Planets

• We will discuss the different planets in the
  future chapters.
• Basic information regarding the two families
• Terrestrial Composed of rock
• 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.

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Terrestrial planets

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The Outer Planets - Jovian

• Jovian Planets composed of ice
• Ice frozen liquids and gases.
• 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

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The Jovian Planets

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Satellites

• 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
• Planets of Moons
• Jupiter 39
• Saturn 30
• Uranus 21
• Neptune 8
• Mars 2
• Earth 1
• Pluto 1

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Answer the questions in your notes. I will come
around to check

• 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.

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Asteroids

• 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 Jupiters gravity prevented it from
  occurring.

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Comets

• 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 40,000-100,000
  AU from the Sun.
• If a comet doesnt 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.

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Bodes Law

• 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.

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Odds and ends of the chapter

• 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).

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Odds and ends of the chapter

• 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

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Other planetary systems

• 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.