PCS 181 Lecture Notes - Lecture 6: Baryon, Observable Universe, Electromagnetic Spectrum
15 Dec 2017
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Unit 4- birth of stars feb 23 rd. Interstellar matter- the dust and gas that occupy space between stars. Stars form in this dust/gas in clouds (neblue) in space. Dust- ~1% of total visible mass in space, out of 4% known baryonic matter. Mixture of : tiny grains of dirty ice, carbon, silicate particles, and comples particles. Interstellar reddening - light from star passes through the dust. Dust same wave length as blue and it scatters , blue light more than red making it appear redder than it is bcuz more red light comes through. Gas - there are 100 times more gas mass than dust mass in universe. This visible universe contains 75% hydrogen, 24% helium and 1% everything else. Hi (h1) rregions- neutral (non-ionized ) hydrogen clouds. Cold hydrogen gas is in cold state (n=1 orbit) Emit wave length ^= 21 cm (radio region) Excess energy is realeased as bursts of raddation.
