Multiple Choice
Why is it surprising that spiral arms are stable structures, lasting billions of years?
A) Differential rotation should tear the arms apart.
B) Gas and dust clouds should run out of material to make young stars.
C) Supernova explosions should disrupt the arms.
D) Globular clusters are continuously passing through the arms.
E) Gravity should pull the arms down into the center of the galaxy.
Correct Answer:

Verified
Correct Answer:
Verified
Q1: Which statement about stellar populations is correct?<br>A)
Q2: A "galactic fountain" is _.<br>A) a stream
Q3: Match the regions of the galaxy listed
Q4: The best explanation for the activity at
Q5: _ are crucial in determining the distance
Q7: Stars that formed in the very early
Q8: Spiral arms are obvious-easily-seen features-because they contain
Q9: Spiral density wave theory and self-sustaining star
Q10: The center of the galaxy has been
Q11: How have astronomers determined the mass of