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Lecture 6

Introduction to Astronomy-Lecture 6 Notes!.docx

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PCS 181
Margaret Buckby

UNIT # 4: Birth of Stars….lives of Stars: Interstellar Matter:  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:  Dust is ~ 1% of the total visible mass in space.  Obscures our view of distant objects.  Is mixture of:  Elongated, tiny, grains of dirty ice.  Grains of graphite (Carbon).  Silicate particles.  Complex molecules. Interstellar Reddening:  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. Gas:  There is ~100 times more gas mass than dust mass in the universe.  Gas ~100 Dust  The visible universe contains:  ~75% Hydrogen.  24% Helium  < 1% Other. Hi Regions:  These are clouds of neutral (=NOT ionized, Hydrogen).  Contain ~ 1% M to 100M o o.  Thecold Hydrogen gas in its ground state (n=1 orbit).  Spin Flip of Hydrogen:  Parallel Spins. Anti-parallel spins (a lower energy state).  The electron can undergo a spontaneous “spin flip”.  From the aligned (=par
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