Our Evolving Universe
Self Test 9

1. Elliptical galaxies are believed to be created by mergers because
   1. they are more common in rich clusters where galaxies are closely spaced
   2. they are more massive than spiral galaxies
   3. they are younger than spiral galaxies
   4. more than one of the above
   
   
2. If spiral galaxies form from the collapse of a rotating cloud of gas, globular clusters form
   1. after the galaxy has settled into its final shape
   2. during the initial collapse
   3. in the disc, but are ejected later by interactions with other galaxies
   4. none of the above
   
   
3. Galaxy collisions
   1. cause bursts of star formation
   2. are more common in the early universe (i.e. in very distant clusters)
   3. can account for the faint "shells" of increased stellar numbers found in some elliptical galaxies
   4. more than one of the above
   
   
4. Active galactic nuclei are more common in very distant galaxies because
   1. central supermassive black holes are rare, so most nearby galaxies don't have one
   2. any galaxy containing a central supermassive black hole is eventually swallowed up by the hole, so these galaxies only exist in the early universe
   3. the activity lasts only until the region of space near the black hole runs out of gas
   4. the black hole eventually escapes from the galaxy
   
   
5. As a satellite of the Milky Way, the Large Magellanic Cloud might be responsible for
   1. generating our spiral structure
   2. eventually transforming us into an elliptical galaxy
   3. moving the globular clusters out of the disc
   4. making the disc rotate faster

out of 5.

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