HW #10 Solutions
•Question 8   (1 point) One fundamental requirement for an object to be a good tracer (i.e. marker) of the galaxy's spiral arms is that it be
 a.moving with small radial velocity (relative to earth).   b.moving with large radial velocity (relative to earth).   c. a short lived and therefore young object.   d. a very long lived and therefore probably old object.   
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•Question 9  (1 point) What is the most common type of galaxy, based on what we see in our own Local Group?
a. irregular galalaxies   b. flocculant spiral galaxies   c. grand design spiral galaxies   d. giant ellipticals   e. dwarf ellipticals   
•This one you should know from the figure of the Local Group in the slides/text.  I’d make sure I knew this for the exam!
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• Question 10 (1 point)   Observations of galaxies and clusters of galaxies indicate that roughly ____ percent of the universe is dark matter.
 
a.5%b.25%c.50%d.75%e. 95% 
•You have to look this one up, but it is a number you should know.