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We Discover the Galaxies

We Discover the Galaxies. Galactic or Extragalactic? -- the nature of the “nebulae” The Shapley – Curtis Debate 1920 . Resolution of the controversy -- Cepheid variables in M31 and M33 Hubble 1923 – 24 using the new Mt Wilson 100-inch telescope .

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We Discover the Galaxies

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  1. We Discover the Galaxies Galactic or Extragalactic? -- the nature of the “nebulae” The Shapley – Curtis Debate 1920 Resolution of the controversy -- Cepheid variables in M31 and M33 Hubble 1923 – 24 using the new Mt Wilson 100-inch telescope

  2. Morphological Classification of Galaxies -- Hubble Spirals, Ellipticals and Irregulars Spiral Galaxies – normal and barred Based on size of nuclear bulge and openess of the arms Sa -- large bulge, tightly wound arms

  3. Spiral Galaxies Type Sb

  4. Spiral galaxies -- Types Sc and Sd small bulge, very open fragmented arms

  5. Barred Spirals

  6. Elliptical Galaxies -- giants and dwarfs Classification based on degree of ellipticity or flattening

  7. Irregular Galaxies

  8. Magellanic Irregulars

  9. Hubble’s Tuning Fork Diagram

  10. The Milky Way ?? Edge-on Sc Milky Way -- infrared SBbc type

  11. Galaxy Clustering Local Group of Galaxies -- 3 spirals + > 30 small Irr and dEll Virgo Cluster

  12. Rotation Curves and the Missing Mass

  13. Gravitational Lensing

  14. Einstein ring 

  15. Missing Mass in Galaxy Clusters and missing mass in halos of galaxies ? “cold dark matter” -- CDM WIMPS (weakly interacting massive particles) or MACHOS (massive compact halo objects)

  16. Distance – Redshift Relation or Hubble Law Slipher at Lowell Obs first noticed the redshift several years earlier

  17. A linear relation Vel = constant x Distance Constant = slope – km/sec/Mpc (Hubble Constant) V = H x D The inverse ? 1/H Time -- expansion age of the Universe

  18. H = 73 – 75 km/s/Mpc and 1/H ~ 13 – 15 x 109 yrs

  19. Galaxy Clusters, Superclusters and Large Scale Structure

  20. Large Scale Structure of the Universe from redshift surveys

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