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. We know about the black hole in the Galactic Center because
a. It glows brightly
b. Shapley found it
c. from Newton's and Kepler's laws
d. because we see a dark spot where it bends the light away
e. because we have seen things get sucked into it
2. When matter falls into a black hole
a. it quickly disappears from sight
b. great amounts of energy can be released
c. it passes out into another Universe
d. it takes an unfamiliar form
e. its light shifts to the blue
3. Superluminal - faster than light - motions result when
a. the geometry of motions sets up an optical illusion
b. matter falls into a black hole
c. there is such a violent explosion that pieces are expelled faster than light
d. Einstein's laws are broken
e. neutrinos are accelerated to a very high speed
4. The nature of quasars was initially confusing because
a. their emission lines were at peculiar wavelengths
b. they were radio sources
c. they varied rapidly
d. they were very luminous
e. they looked like stars
5. An active nucleus can be identified by
a. bright and broad emission lines
b. radio jets emerging from the nucleus
c. a bright source that varies rapidly
d. strong X-ray emission
e. all of the above
6. Active galaxy nuclei are powered by
a. matter falling into a very massive black hole
b. lots of star formation
c. energy left over from when the galaxy formed
d. radio jets extending out into space
e. galaxy mergers
7. Jets emerging from an active nucleus contain particles moving nearly at the speed of light because
a. that is the only way to account for their apparent superluminal motions
b. that is how they can get so far from the galaxy
c. we measure extreme Doppler shifts in their emission lines
d. it accounts for their prominence in the radio region
e. both a. and d.
8. A good way to look for a massive black hole in the nucleus of a galaxy is to look for
a. a dark spot projected against the starlight of the galaxy
b. a tight knot of stars being sucked into the gravitational field of the black hole
c. lensing of background galaxies behind the nucleus
d. distortions in the shape of the galaxy due to the large gravitational field
e. very large Doppler shifts in the spectra of stars close to the center of the galaxy
9. The rapid variability in the outputs of quasars and other active nuclei shows that
c. the nuclear sources are very small
d. stars are blowing up in these regions
e. the apparent variability is an effect of gravitational lensing
10. The clearest evidence that quasars are at great distance is
b. that they lie in the centers of galaxies that are at large distances
c. that their emission lines are shifted to the red
e. the faintness of the Cepheid variables in them
11. In comparison with the black holes in some other galaxies, the one in the Galactic Center is curious because
b. it is harder to study in any detail
c. it seems to be making very little energy
d. it occasionally has a huge outburst
12. The Galactic Center was hidden from astronomers for many years because
a. it only emits in the radio and infrared
b. it is a very diffuse region that is hard to pinpoint
c. there were looking in the wrong places
d. the Milky Way has a peculiar, atypical structure that made it hard to find
e. it is hidden in the visible by clouds of interstellar dust
13. A black hole can glow in an active nucleus when
a. light escapes from within the event horizon
b. it lenses the light from objects behind it
c. friction heats matter falling into it to very high temperature