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Announcements

Announcements. 4th test is finished! Please pick up graded work Homework 12 due Monday (requires internet use) Second project is due in two weeks Please reread lyrics to Monty Python galaxy song; document the inconsistency for a free Milky Way bar!. Galaxies. 17 November 2006. Today :.

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Announcements

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  1. Announcements • 4th test is finished! • Please pick up graded work • Homework 12 due Monday (requires internet use) • Second project is due in two weeks • Please reread lyrics to Monty Python galaxy song; document the inconsistency for a free Milky Way bar!

  2. Galaxies 17 November 2006

  3. Today: • The “spiral nebulae” • Measuring distances to galaxies • Rotation rates and “dark matter”

  4. Messier Catalog • 27 “open” clusters • 29 globular clusters • 6 diffuse nebulae • 4 planetary nebulae • 1 supernova remnant • 2 small groups of stars • 40 other fuzzy things in which no individual stars are visible

  5. The Discovery of Spiral Structure Lord Rosse, 1845

  6. What are the spiral and elliptical nebulae? • No individual stars are visible, even in largest telescopes • Some have spiral structure, as if spinning rapidly • Visible amount of rotation over a few decades? • Continuous spectra • Hypothesis 1: Swirling clouds of fluid, possibly forming new solar systems • Hypothesis 2: “Island universes,” similar to our own Milky Way star system

  7. Island Universes Confirmed! Edwin Hubble discovers Cepheid variable stars in the Andromeda Nebula, 1923 Estimated distance: 1 million light-years (actually 2 million) Edwin Hubble, 1889 - 1953

  8. Finding the Andromeda Galaxy

  9. Finding the Andromeda Galaxy

  10. Finding the Andromeda Galaxy

  11. Finding the Andromeda Galaxy

  12. The Andromeda Galaxy

  13. The Andromeda Galaxy

  14. The Andromeda Galaxy

  15. The Magellanic Clouds

  16. Hubble Space Telescope can detect Cepheids out to 60 million light-years (Virgo Cluster)

  17. Virgo Cluster

  18. NGC 253

  19. Whirlpool Galaxy (M51)

  20. M83

  21. M104 (Sombrero Galaxy)

  22. Edge-on galaxies

  23. Barred spiral galaxies

  24. Colliding Galaxies

  25. Galaxy with dust lane

  26. Group of galaxies in Leo

  27. Beyond 50 million light-years, the best standard candles are type-I supernovas

  28. Coma Cluster

  29. Coma Cluster

  30. Hubble Deep Field

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