Thermal Radiation: Kirchhoff's Law

• thermal vs blackbody emitters
• example: Cas A X-ray spectrum

Two-Level Systems: Spectral Lines

• spontaneous and stimulated emission
• Einstein coefficients
• spectral line examples
  • ionized hydrogen = HII region
  • the Sun: spectral overview, zoom, continuum and line imaging
• astrophysical masers: AGN NGC 4258, AGB star TX Cam movie and caption (Gonidakis, Diamond, & Kemball 2013)

Scattering

• coherent isotropic scattering
• awesome example: reflection nebulae
  • Pleiades optical, IR
  • Blue Horsehead
  • Iris
• awesome example: light echo
  • variable star V838 Mon image, movie
  • light echo from SN 1987A
  • Circinus X-1
  • Cas A
  • random walks
  • scattering and absorption: albedo