Astrophysics and Cosmology

• Stellar luminosity


  The amount of light emitted by a star
• Star formations


  • Gravity causes nebula to collapse
  • GPE becomes KE, temperature increases
  • At 10,000,000K, hydrogen begins fusing into Helium
• Gravity


  Radiation pressure
• Main sequence


  A star's period of stable hydrogen fusion
• Luminosity of main sequence stars is approximately 4x10^T
• Hertzsprung-Russell diagram


  A plot of stellar luminosity vs temperature that shows different stages of stellar evolution
• Stages of stellar evolution

  • Main sequence
  • Dwarfs
  • Supergiants
  • Giants
• Decreasing temperature as stars evolve off the main sequence
• Evolution of low mass star

  1. Main sequence

  2. Red giant

  3. Planetary nebula

  4. White dwarf
• Evolution of massive star

  1. Main sequence

  2. Supergiant

  3. Supernova

  4. Neutron star

  5. Black hole
• Absorption line spectra


  White light passing through cold gas absorbs specific wavelengths of light as it excites electrons
• Emission line spectra


  De-exciting electrons emit light of specific wavelengths