8- Evolution of low-mass stars

Learning goals

  • Estimate the main-sequence lifetime of a star from its mass.
  • Explain why low-mass stars grow larger and more luminous as they run out of fuel.
  • 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. The life of a main-sequence star depends on its mass.
    • Observing stellar evolution.
    • Main-sequence lifetime.
    • Changes in stellar structure.
  2. The star leave main-sequence.
    • Electron-degenerate matter in the helium core.
    • Hydrogen shell burning
    • The red giant branch of the H-R diagram.
  3. Helium burns in the degenerate core.
  4. Helium burning and the Triple-Alpha process
    • The helium flash
    • The horizontal branch
    • The lowest-mass stars.
  5. Dying stars shed their outer layers.
    • Asymptotic Giant Branch
    • Planetary nebula stage.
    • White dwarfs.
    • The fate of the planets.
  6. Binary stars
    • Mass flows from a large star onto to its smaller companion.
    • Evolution of a close binary system.
    • Novae.
    • Type Ia supernovae.

Activities:

  • Unit notes folder
  • Read chapter 16
  • Color Magnitude Diagram (CMD) of the Jewelbox Cluster
  • ClassAction: Stellar Evolution (Lessons 1-6, 8 // 13-15; C1-3)
  • Nebulae Shapes: See instructions for #49 on page 476 of your textbook. Copy your three images into a word document and annotate, then submit to D2L.
  • Teams work on their presentations.

Extra Stuff