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{\bf 29:120 Introduction to Astrophysics II\\
     Spring 2009\\
     First Hour Exam \ldots February 19, 2009}
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Start each question on a new page.  It allows me to make comments and generally keeps me in a better mood.  Write legibly. Explain what ideas you are using and what you are trying to do. There are 6 questions.   Good luck and no whining.
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{\bf Walk with Ursus!!!}
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(1) Explain why it is easier to solve for the structure of a white dwarf star than it is for a main sequence star.  Your discussion should use mathematical concepts, although a full derivation is not expected. \\

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(2) What is the primary type of radiation used to study molecular clouds.  Explain how this radiation arises from molecules.  How can we determine the temperature of the gas in molecular clouds? What is the approximate temperature (rough range) in parts of a molecular cloud where stars form? \\

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(3) Describe a very basic, but convincing {\em observation} that molecular clouds are associated with the process of star formation.  \\


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(4) What is the Triple Alpha Process?  Is it relevant at any time in the evolution of the Sun? If so, describe when and why. \\

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(5) Explain why an O5 main sequence star will have a larger HII region than the Sun, if both stars are placed in an identical cloud.  Use physics in your answer.  Use as many equations as you can remember.    \\

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(6) What do we mean by the term ``extinction of light'' in astronomy and atmospheric physics?  What processes are occurring in extinction?     \\

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