Use these questions to test your understanding. If you get them wrong, you will be linked back to the relevant part of the notes. 

Be sure you study them thoroughly (don't just get a quick fix for your mistake) so your overall understanding is improved.

1. When galaxies collide

   a. they explode

   b. they pass right through each other with no other consequences

   c. they tend to merge into a single galaxy

   d. there is a loud noise

   e. this happens so seldom we do not have a good idea of what happens

2. Galaxies undergoing starbursts

   a. are full of bursting stars

   b. are usually ellipticals

   c. were identified through clusters of stars bursting out from them

   d. are forming massive stars rapidly and in exceptionally large numbers

   e. have less dark matter than other galaxies

3. Our own galaxy

    a. is "safe" from colliding with other galaxies for the foreseeable future

    b. is pulling apart some nearby galaxies and will eventually consume them

    c. is being pulled apart by the Andromeda Galaxy

    d. is highly distorted due to a very recent collision with a large galaxy

    e. we cannot tell if it is undergoing a collision with a galaxy because of the obscuration by interstellar dust

4. Spiral arms are

    a. where the dust in a galaxy is thin enough that we can see the stars better

    b. where stars from galaxies that have recently collided are spiraling into the center

    c. where stars tend to form

    d. the result of ejections from spinning black holes in galaxy nuclei

    e. a mystery to astronomers

5. Galaxies can merge when

    a. They fall into a black hole

    b. They collide with each other and their stars combine into binaries

    c. They collide and much of their kinetic energy is transfered to stars that are thrown out into space

    d.  Their interstellar clouds join together to make a new galaxy

    e.  One of them accretes another.

6. Ring-shaped galaxies and galaxies with tails of stars are evidence for

    a. galaxies forming from intergalactic matter

    b. nuclear activity in galaxies

    c. explosions across the face of previously normal galaxies

    d. galaxies taking part in the expansion of the Universe

    e. galaxy collisions

7. Star formation

    a. occurs equally at all places in the disks of spiral galaxies

    b. tends to be enhanced where peaks in the local density compress the molecular clouds

    c. occurs wherever there is atomic hydrogen

    d. occurs where halo stars collide with the disk

    e. occurs in formations that spread into spiral arms due to the flat rotation curves of these galaxies

8. Galaxy collisions can

        a. trigger high rates of star formation

        b. perturb the planets orbiting stars in the colliding galaxies

        c. drag most of the interstellar gas of the galaxies out of them

        d. destroy the bulges of the galaxies

        e. tear the galaxies apart so there is nothing left