PCS 181 Lecture Notes - Lecture 6: Observable Universe, Unit, Protostar
21 Mar 2013
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This is dust and gas that occupy space between the stars. Stars form out of the dust/gas in space. We examine the nature of the dust and gas separately. Dust is ~ 1% of the total visible mass in space. Light from a star passes through the dust. The dust particles are ~ same length as blue delta"s. The dust scatters blue delta"s more than red delta"s. *note: above last bulletin is on test # 2 question! A larger number of red photons pass unhindered through the dust and reach the observer. Star appears redder than it actually is. There is ~100 times more gas mass than dust mass in the universe. These are clouds of neutral (=not ionized, hydrogen). The cold hydrogen gas in its ground state (n=1 orbit). The electron can undergo a spontaneous spin flip . From the aligned (=parallel) state to the. Excess energy is released as a tiny burst of radiation.
