PHYS 1000 Lecture Notes - Lecture 11: Interstellar Cloud, Emission Nebula, Interstellar Medium
12 Feb 2018
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Document Summary
The interstellar medium is the medium the matter between the stars. It is very low density but there is so much space it adds up. There is as much interstellar matter as there is matter in the stars themselves. This is the region out of which new stars are formed. Also this is where the matter from old stars goes when they die *diagram*. The interstellar medium consists of gas and dust. Gas is atoms and small molecules, mostly hydrogen and helium. The denser component it averages roughly 106 atoms per cubic meter (best vacuum on earth 109). It does not block much electromagnetic radiation except for absorption. Dust is more like soot or smoke; larger clumps of particles. Rarer than the gas averaging about 1 dust particle per trillion or so atoms. A dust grain is usually about 10-7m in diameter and can block electromagnetic waves with similar or smaller wavelengths.
