scales: cosmic. galaxy basics bright galaxies tend to have one of two shapes. spiral 1) spiral...

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  • Slide 1
  • SCALES: COSMIC
  • Slide 2
  • GALAXY BASICS
  • Slide 3
  • Bright galaxies tend to have one of two shapes. Spiral 1) Spiral galaxies, like the Andromeda Galaxy and the Whirlpool Galaxy.
  • Slide 4
  • Stars in a spiral galaxy go around on neat (almost) circular orbits.
  • Slide 5
  • Elliptical 2) Elliptical galaxies, like the galaxy M87. There is also an abundant category of dwarf galaxies, including our neighbors LMC & SMC.
  • Slide 6
  • Stars in an elliptical galaxy are on disordered, randomly oriented orbits.
  • Slide 7
  • SCALE MODEL III
  • Slide 8
  • A great island of stars in space, all held together by gravity and orbiting a common center M31, Andromeda Galaxy
  • Slide 9
  • The sum total of all matter and energy; that is, everything within and between all the galaxies. Most of the space between galaxies is empty. Universe
  • Slide 10
  • Galaxy shrunk to size of small plate That factor is 10 23 or 100,000 billion billion
  • Slide 11
  • Lets lay out the local universe, remembering that each galaxy contains a few billion stars. Use the scale model where a large galaxy is a small plate and a dwarf is a cotton ball to lay out the architecture of the nearby universe.
  • Slide 12
  • Nearest Neighbors
  • Slide 13
  • Local Group
  • Slide 14
  • Virgo Cluster
  • Slide 15
  • Nearby Universe
  • Slide 16
  • This model shrinks the scale by 10 billion from the model of grains of sand as stars. Scale is a phenomenal 1:10 23. The Milky Way is a plate 10 cm across LMC/SMC cotton balls 20 cm away Andromeda is a plate about 3 m away Virgo Cluster is 1000 plates 70 m away Observable universe is 100 km across SPACE SCALE MODEL III:
  • Slide 17
  • Cosmological Principle Isotropic: same at all locations Homogeneous: same in all directions Cosmology is based on the assumption that our location (MW) is typical and not unusual.
  • Slide 18
  • Cosmology assumes we have no special place in the universe, i.e. homogeneity and isotropy. With monks as galaxies, and one acting as the MW, arrange yourselves to be the same in all directions but not all locations, and vice versa.
  • Slide 19
  • Science is Seeing The Universe is Empty The visible universe contains 10 23 stars in 40 billion light years. That is 10 41 km 3 of star stuff in a space of 10 74 km 3. So only one part in 10 33 or a billion trillion trillion contains anything.
  • Slide 20

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