ASTR-1010 Lecture Notes - Lecture 14: Radiography
6 Oct 2016
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Document Summary
Dusty gas clouds obscure our view because they absorb visible light. This is the interstellar medium that makes new star systems. Regions of the milky way galaxy: disk. Location of the open clusters: bulge. Mixture of both young and old stars: halo. A: stars in open clusters because they are younger and therefore formed from more enriched material. The interstellar medium: the stuff between the stars, mostly a vacuum (1 atom cm-3, composed of 90% gas and 10% dust. Dust: large grains made of heavier elements: ism effectively absorbs or scatters visible light, radio and infrared light does pass through ism. We can study and map the milky way at these wavelengths. X-rays from hot gas in supernova remnants reveal newly-made heavy elements. Multiple supernovae create huge hot bubbles that blow out of disk. Gas clouds cooling in the halo rain back down on disk. Radiation from newly formed stars is eroding these star-forming clouds.
