The Solar System

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The Solar System

• Paul J. Thomas
• Department of Physics and Astronomy
• University of Wisconsin - Eau Claire

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Overview

• Sun is 99 of mass of the solar system planets
  are 1.
• Small, rocky, inner planets.
• Large, gaseous, outer planets.
• Asteroid belt between Mars and Jupiter.
• Comets beyond the orbit of Uranus.

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How does a star shine?

• Stars are balls of hot gas. They support
  themselves against gravity by the expansion of
  gas in their interiors.

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How does a star shine?

• The centers of stars must very hot. (The center
  of the Sun is about 15,000,000 K).
• At these temperatures, hydrogen can be converted
  to helium by nuclear fusion.

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Nuclear Fusion

• Mass of 4 protons 2 electrons
• 6.694 10-24 g
• Mass of 4He nucleus
• 6.644 10-24 g
• Difference 0.050 10-24 g
• Energy released (E mc2) 4.4 10-12 J
• 6 1014 g of H ? He per second!

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Energy from Nuclear Fusion

• 4.4 ? 10-12 J for each He nucleus produced
• (there are 1.5 ? 1023 He nuclei per g)
• 6.62 ? 1011 J for each g of He produced
• (6 ? 1014 g of He is produced every second)
• 3.97 ? 1026 W of power

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The Solar Wind and the Aurora
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The Solar Wind and the Aurora
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Inner vs. Outer Solar System

• Inner Solar System
• Silicate mantles, iron cores
• CO2 atmospheres
• Very few rocky satellites

• Outer Solar System
• Gas atmospheres, silicate cores
• H2/He atmospheres
• Many icy satellites
• Rings

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Nebular Hypothesis
Immanuel Kant (1724-1804)
Pierre-Simon Laplace (1749-1827)
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Artists conception of Primitive Solar Nebula
(PSN)
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Planetesimal Accretion
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Volatile-rich accretion in outer solar system
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Capture of H-rich atmospheres by Giant Planets
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Planetary Formation ElsewherePSNs in the Orion
Nebula
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Planetary Formation ElsewhereBeta Pictoris
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The Age of the Solar System

• Radioactive dating techniques provide us with
  ways to measure the ages of rocks
• Generally, the age is the time since the rock
  was last melted
• The age of the solar system can be measured by
  analyzing chondrite meteorites

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Radioactive Dating

• Measures naturally occurring radioactive isotopes
  in rock
• 14C ? 14N t1/25730 years
• 238U ? 208Pb t1/2 4.47 billion years
• 40K ? 40Ar t1/2 1.3 billion years
• 87Rb ? 87Sr t1/2 47 billion years
• After N halflives, (1/2)N of the original isotope
  remains.

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The Age of the Solar System

• Oldest Rocks on Earth
• 4.03 billion years
• Oldest Rocks on Moon (Maria)
• 3.5 billion years
• Oldest Rocks on Moon (Highlands)
• 4.48 billion years
• Oldest Chondrite Meteorites
• (4.566 0.001) billion years

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Types of Rocks

• Igneous
• solidified molten rock
• Sedimentary
• rock altered by wind or water
• Metamorphic
• rock altered by pressure or temperature
• Primitive (Chondritic)
• unaltered by geological activity since the solar
  system formed

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Apollo 11 Mare Tranquillitatis Apollo 12 Oceanus
Procellarum (Surveyor 3) Apollo 14 Fra Mauro
(Mare Imbrium) Apollo 15 Hadley Rille (Mare
Imbrium) Apollo 16 Descartes Highlands Apollo
17 Taurus Littrow (Mare Serenitatis)
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