AST 101 Lecture Notes - Lecture 16: Radiography, Density Wave Theory
Document Summary
Visible light doesn"t reveal all the details of the structure and composition of the. Need to look at galaxy in other wavelengths to see complete picture. Observed from hot gas above and below milky way"s disk. Reveals stars whole visible light is blocked by gas clouds. 21-cm radio waves emitted by atomic hydrogen show where gas has cooled and settled into disk. Radio waves from molecular hydrogen (h2) show locations of molecular arm. Finding star formation in the milky way. The light from massive stars ionizes the gas around them ionization nebulae are therefore a tracer of star formation. Long wavelength infrared emission shows where young stars are heating. Show where cosmic rays from supernovae collide with atomic nuclei in gas. Stellar orbits in the milky way clouds. Stars in disk all orbit in same direction with little up-and-down motion. Orbits of stars in bulge & halo have random orientations.
