The Nebular Theory, Matter, and Light

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The Nebular Theory, Matter, and Light

• Terrestrial, Jovian, and dwarf planets
• Nebular theory
• Matter atoms and molecules
• Kinetic and potential energy
• Electromagnetic spectrum
• Spectroscopy
• Goal du jour
• Understand more about matter, and how we use
  light to study the Universe.

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Four classes of solar system objects

• Terrestrial planets
• Jovian planets

• Dwarf planets
• Jovian moons

3
Solar System models

• A good formation model should explain all these
  things.
• ?See details of the Nebular Theory, p79.
• ? Pay particular attention to origin of two types
  of planets.

4
The basics of matter

• Atoms
• Often considered the building blocks of matter,
  but atoms have internal structure.
• Atoms consist of a nucleus, and a surrounding
  cloud of electrons.
• The atomic nucleus
• Protonsmassive, charge
• Neutronsmassive, no charge
• Electrons
• Low mass, - charge
• of electrons of protons

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The basics of matter
4 2
Elemental notation He
1H 1 proton (and 1 electron) 2H 1 proton, 1
neutron (and 1 electron) 4He 2 protons, 2
neutrons (and 2 electrons) Isotopes The same
element (proton ), but different masses (i.e.,
different numbers of neutrons). Ex
He Ions Atoms temporarily stripped of one or
more electrons.
3 2
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The basics of matter

• Molecules are atoms that have been bound together
  by mutual attraction.
• Simple compounds
• O2, N2
• Complex compounds
• CO2, H2O, C12H22O11 (sucrose), DNA
• Organic compounds
• Contain C-H bonds

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Phases of matter
Phases Solid Liquid Gas (Plasma)
Solid
Freezing? ?Melting
Sublimation? ?Deposition
Evaporation? ?Condensation
Liquid
Gas
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Types of energy

• Kinetic EnergyEnergy exhibited by motions
  speed, vibrations, rotations.
• Potential EnergyStored energy at the top of a
  hill, a compressed spring, Emc2
• Radiative EnergyEnergy stored in photons,
  technically in each photons magnetic and
  electric fields, hence electromagnetism.
• TemperatureA measure of how much kinetic energy
  is in a sample of molecules

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Electromagnetic Radiation

• Photon
• A self-propagating packet of pure energy.
• c
• All photons all travel at the speed of light,
  the highest speed at which anything in the
  universe can travel.
• Frequency
• Higher energy photons have a higher frequency.
• Wavelength
• Higher energy photons have smaller wavelengths.
• Types of electromagnetic radiation
• radio? microwave ? infrared ? ROYGBIV ?
  ultraviolet ? x-rays ? Gamma rays

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Spectra

• Spectrum
• A graphical display of the different kinds of
  photons in a beam of radiation.
• It might be portrayed as a line-graph, or (if
  visible light) as a multicolored display.
• This kind of smoothly varying, peaking spectrum
  is called a continuum spectrum.
• Continuum spectra are produced by opaque, glowing
  objects.

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Continuum spectra

• The wavelength peak of a spectrum is affected by
  the glowing objects temperature.
• Very hot objects glow blue.
• ?We can take the temperature of objects by
  looking at them!

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Electrons in atoms

• To understand the other kinds of spectra, we must
  first understand how electrons in atoms interact
  with photons.
• Electrons can jump from one level to another in
  atoms.
• An electron dropping towards the atom releases
  energy in the form of a photon.
• An electron must absorb a photon in order to jump
  to a larger orbit.
• Every different kind of element has a different
  set of electron orbit sizes. This will be useful.

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Types of spectra

• Continuum spectrum
• An opaque object will produce a continuum
  spectrum.
• Emission spectrum
• A transparent gas cloud, excited by some energy
  source, will produce an emission spectrum.
• Absorption spectrum
• A continuum source, with a transparent gas cloud
  in front it, will produce an absorption spectrum.
• Chemical analysis
• Since every atom has its unique set of electron
  orbits, each atom has a characteristic spectrum.
• ?We can learn about the composition of gas
  clouds, or planets, or stars in space by looking
  at them!

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Gas discharge tubes

• Gas normally does not conduct electricity
• 1)High voltage applied across gas drives
  electrons across the gap.
• 2)Electrons ram into the gas atoms in the tube,
  exciting the bound electrons (i.e., gives the
  electron energy).
• 3)The bound electron settles back to its ground
  level, releasing the stored energy as a photon.
• 3)Repeat