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{\bf Introduction to Astrophysics I, 29:119\\
     Fall, 2006\\
Ninth  Homework Set...December 1, 2006.\\ Due December 7, 2006}\\
{\em `` A homework set that will live in infamy \ldots''}
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Show calculations and give reasons for your answers. Don't go around 
confused and despondent; if you do not know how to get started, ask me for help. All problem numbers refer to the first edition of the book.\\


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{\bf (1)} Verify the statement made in class that the main sequence lifetime of the Sun would be about 200 years, if it operated with a chemical reaction fuel cycle, which has an energy yield of $\simeq 10^{10}$ ergs/gm. \\

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{\bf (2)} What is the potential energy released if the Sun contracted from its present size to that of a white dwarf star?  Approximate the stars in both cases by uniform spheres. \\

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{\bf (3)} The ``Triple Alpha Process'' is a nuclear reaction sequence by which $^4He$ fuses to form $^{12}C$ (see eq 10.55). Calculate the energy yield in ergs/gram obtainable from this fusion reaction.   \\ 

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{\bf (4)} Problem 10.1 from textbook \\

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{\bf (5)} Problem 10.4 from textbook\\

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{\bf (6)} Problem 10.6 from textbook \\

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{\bf (7)} Use the chemical abundances of the Sun in Table 9.2.   Demonstrate the truth of the statement in the textbook (p326) that 
\begin{equation}
\left< \frac{1+z}{A}\right>_i \simeq \frac{1}{2}
\end{equation}\\

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{\bf (8)} Given the result from problem \# 7 and the data in Table 9.2, calculate the mean molecular weight for fully-ionized solar material. \\

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