11. Galaxies

Learning goals

  • Determine a galaxy’s type from its appearance, and describe the motions of its stars.
  • Explain the distance ladder and how distances to galaxies are measured.
  • Describe the evidence suggesting that galaxies are composed mostly of dark matter.
  • Discuss the evidence indicating that most large galaxies have a supermassive black holes at their center.
  • Understand the structure of the Milky Way Galaxy as a case study for other large galaxies.
  • Explain the evidence for a dark matter halo and for the supermassive black hole at the center of the Milky Way Galaxy.
  • Describe how the motion of the observer affects the observed velocity of objects.
  • Discuss the observable consequences of the relationship between space and time.
  • Explain how gravity is a consequence of the way mass distorts the very shape of spacetime.
  • Explain why the most massive stars end as black holes, and describe the key properties of these stellar black holes.Sketch post-main-sequence evolutionary tracks on the H-R diagram.
  • List the stages of evolution for low-mass stars.
  • Describe how planetary nebulae and white dwarfs form.
  • Explain how some close binary systems evolve differently than single stars.

Outline

  1. Galaxies come in different shapes and sizes.
    • The discovery of galaxies in the 20th century.
    • Types of Galaxies: the Hubble Tuning Folk
    • Stellar motions and galaxy shape.
  2. Finding the distances to galaxies.
    • The distance ladder.
    • Hubble’s Law.
  3. Dark matter in galaxies.
    • Determining the mass of a galaxy.
    • Dark matter detection.
    • Candidates for dark matter.
  4. Galactic supermassive black holes.
    • Discovery of quasars
    • Active galactic nuclei
    • Supermassive black holes and accretion disks.
  5. Case Study: The Milky Way Galaxy
    • Age and compositions of stars
    • Disk verses Halo starts.
    • Dark matter halo and supermassive black hole.

Activities:

  • Unit notes folder
  • Read chapter 19 and 20.2, 20.3
  • ClassAction: Galaxies (Lessons 1-7, 13)
  • LT: Galaxy Classifications (pg. 139)
  • LT: Hubble’s Law Part 1 (pg. 155)
  • Lab 9: Galaxies
  • LT: Dark Matter (pg. 145)
  • ClassAction: Galaxies (Lessons 1-5)

Extra Stuff