Study Guide for Quiz 3:
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The Milky Way & Andromeda
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  Common Properties of the Milky Way & Andromeda Galaxies

  Disk & Spheroid Structure of the Galaxy

  Pop I Stars: 
    Young, metal-rich, disk stars
    Ordered, nearly circular orbits in the disk

  Pop II Stars:
    Old, metal-poor, spheroid stars
    Disordered, elliptical orbits in all directions

  Chemical Evolution, connection to stellar populations

  Supermassive Blackholes

Spiral Galaxies
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  Disk & Spheroid Components
    Thick disk of stars, thin disk of dust, spiral arms
    Spheroid: bright central Bulge and faint extended Halo

  Rotation of the Disk
    Differential Rotation Pattern
    Orbital period of the Sun in the Galaxy
    Measurement of Galaxy Masses from Rotation Curve,
       Doppler effect

  Spiral Arms:
    Outlined by O&B Stars, HII Regions, Gas & Dust clouds
    Spiral Density Waves in the Disk
    Sites of recent star formation.
    Why O&B stars don't move very far from their birthplaces.
    HI, HII, and H_2 gas.


Types of Galaxies
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  Three basic types of Galaxies:
    Spirals
    Ellipticals
    Irregulars

  Dwarf Galaxies

  Differences between the types of galaxies in terms of
    Relative Gas content
    Star Formation History
    Internal Motions
    Structure


Groups & Clusters of Galaxies
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  Galaxies tend to group into Clusters

  The Milky Way is part of the Local Group

  Hierarchy of Structure:
    Groups: < 30 bright galaxies, many dwarfs
    Clusters: 30 - 100's of bright galaxies, many dwarfs
      Where Ellipticals & Spirals are found in Rich Clusters
    Superclusters: Clusters of Clusters
    Voids, Filaments, & Walls, porous structure of the universe
  
Interacting Galaxies
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  Tidal Interactions occur between Galaxies
    Frequency of occurence: the relative distance
      between galaxies is small, particularly in 
      comparison with stars.
    Cause of most of the "peculiar" galaxies observed
    Tidal distortion in encounters

  Types of interactions
    Close Tidal Encounters
    Galaxy-Galaxy Collisions

  Starbursts induced by interactions
    Stars pass through during a collision, but the 
    gas shocks and forms lots of stars.
   
    Drive metal-rich winds into the inter-galactic medium.

  Mergers & Galactic Cannibalism
    How we think massive ellipticals are made.



Active Galaxies & Quasars
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  Found in a small fraction of all galaxies
    Compact source of energy in the nucleus.
    Include the most luminous objects known.
    How they shine.

  Types:
    Quasars: Quasi-stellar Radio Sources
    Radio-Quiet Quasars (QSOs), Radio Galaxies

  Power source:
    Supermassive Black Holes
    Accretion Disks
    Radio Jets


Special Relativity:
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   First Postulate (uniformly moving observers)
   Second Postulate (speed of light)
   Newton's conception of absolute space & absolute time
   Einstein's conception of space & time as relative
   How time appears to different observers (the photon clock experiment)
   



General Relativity:
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   Shortest paths in curved spacetime
   Explanation of gravity as curved spacetime
      Matter tells spacetime how to curve, 
      Curved spacetime tells matter how to move.
   Experimental verification of GR:
      Perihelion shift of Mercury
      Bending of Starlight near the Sun 
      Strong gravitational lensing of galaxies by clusters




Einstein's Cosmology:
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   Cosmological Principle:
      Universe is Homogeneous and Isotropic on Large Scales
   Cosmological Constant
   Evidence of large-scale homogeneity & isotropy





Observational Cosmology:
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   Hubble's Law
   Hubble Parameter, H0
      How it is measured
      Uncertainties in measuring H0
      Current rate of expansion of the Universe
      We are not at the center: raisins in expanding cake, 
	 points on expanding balloon, etc.
   Redshift distances
   Redshift maps




Tests of the Big Bang, Cosmic Timeline, Early Universe
Big Bang Theory:
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   Basic features of the theory
   Expansion of the Universe (Hubble's Law)
   Densith Parameter (Omega0)
      Critical Density
      Omega0 determines the geometry of the Universe
   Age of the Universe (Hubble Time)
   
   Primordial (Big Bang) Nucleosynthesis
      Production of Deuterium, Helium, and light metals (Li,Be,B)
      Predictions for observed abundances
	Comparison with predictions
     
   Cosmic Background Radiation
      Blackbody Spectrum & Temperature
      Observed properties 
      Conditions at the Epoch of Recombination