ASTRO-110 Chapter Notes - Chapter 3: H Ii Region, Milky Way, Spiral Galaxy
Document Summary
We know that we reside in a spiral galaxy that is about 100,000 light years across. Warm, unionized atomic hydrogen gas (h i region) fills much of the galactic disk (1 atom/cm^3, 10,000 k) Cooler regions of atomic hydrogen are even more dense (100 atom/cm^3, 100k), densities this high around star forming regions. Dust accounts for about 1% of the mass of an atomic cloud. However it is the primary reason these clouds can be opaque to shorter wavelength visible, uv and x-ray radiation it is widely believed this dust originates in the strong solar winds of red-giant stars. In particular, those that have finished fusing their helium cores and have an abundant supply of carbon. The interstellar medium and stars interstellar medium is the source for all of a star"s material the lives and deaths of stars strongly affect the interstellar medium.
