Homework # 9, due 3 May
1. Do problem 5.8 in the text.
2. Do problem 5.13 in the text. Determine the ratio of the two areas
of the zones in the disk where 2 and 4 armed spirals are stable.
Does this depend on the value of Ωp ?
3. Do problem 5.15 in the text. Specifically, find
i) the radius of the inner edge of the disk in parsecs
ii) the mass inside this disk
iii) and the mean time between collisions of stars assuming
each star is 1 M⊙.
iv) Also find the mean distance between these stars.
4. Suppose the true aspect ratio of a type of galaxy was B/A = 1/2.
If we observe a large number of these galaxies, each having a
randomly oriented inclination i, what is the average aspect ratio
q that we would observe? Even if you can’t determine the number,
is q larger or smaller than B/A?