PH109 Exploring the Universe, Fall 04, test #4
Please indicate the best answer to the following questions on the answer sheet provided.
1. Which of the following is not a characteristic of the stars of the disk component of our galaxy?
a. circular orbits,b. randomly inclined orbits, c. higher metal abundance d. young stars,
2. The mass of a single galaxy might be found by
a. the double galaxy method, b. the rotation curve method, c. the cluster method. d. any of these
3. Most of the mass of a galaxy is
a. contained in the massive O and B stars in the galaxy.
b. contained in the H I regions of the galaxy.
c. contained in the H II regions of the galaxy.
d. contained in the dark matter of the galaxy.
4. For what type of object is the period-luminosity relation used for determining distances?
a. Algol variables, b. Cepheids, c. Cataclysmic variables, d. 21 centimeter radiation.
5. Why is our galaxy in the shape of a disk
a. because it rotates
b. because it got sheered off during a galactic collision
c. the outer parts were torn away by the Magallenic clouds
d. the dark matter holds it in that formation
6. The two dwarf irregular companions of the Milky Way Galaxy are known as the
a. bi-polar nebular, b. M31 and M32, c. Happy and Sleepy, d. large and small Magellanic clouds
7. The distribution of matter in a galaxy can be found by measuring
a. the number of stars, b. the rotation curve c. number of pulsars, d. how thick a galaxy is
8. 21 cm radiation is produced by which element?
a. hydrogen, b. helium, c. carbon, d. iron
9. The oldest stars in the galaxy are found
a. in globular clusters in the halo, b. at the center of the galaxy
c. on the front rim of spiral arms, d. in the galactic disk
10. What is the name of the nearest large galaxy to our own
a. Milky Way, b. Andromeda, c. Orion, d. Cygnus
11. If a galaxy is determined to be 2 million light years away, what does that mean
a. it takes light 2 million years to cross the galaxy
b. stars did not turn on till about 2 million years ago
c. it takes light 2 million years to reach us from the galaxy
d. if we could put our galaxy 2 million light years away it would look as bright as that galaxy.
12. Hubble’s law states that:
a. putting telescopes in space will cost approximately ten times more
b. the recession of one galaxy must equal the precession of another
c. the faster a galaxy moves away from us the more massive it is
d. the faster a galaxy moves away from us the farther away it is
13. The size of our galaxy is about
a) 3 light years, b) 120 thousand light years, c) one mega parsec, d) unknown at the present
14. What type of galaxy is the Andromeda galaxy M31?
a) spiral, b) globular, c) elliptical, d) irregular
15. The location of our Sun in the galaxy is approximately
a) near the core, b) near the outer edge
c) about 2/3 of the way out to the edge, d) not currently determined
16. About how long does it take for the Sun to complete one trip around the galaxy?
a) 25 thousand years, b) 2.5 million years, c) 250 million years, d) 25 billion years
17. The radio emission from radio galaxies and quasars is due to
a) thermal emission, b) blackbody radiation, c) O and B stars, d) synchrotron radiation
18. How do we know that the quasars are at large distances?
a) they are extremely dim, b) they have large redshifts,
c) they have large parallaxes, d) they are greatly obscured by interstellar dust
19. What is hardest to explain about spiral arm structure
a) that they ever existed in the first place, b) why galaxies only have two of them
c) why they have sharp boundaries, d) how they maintain themselves
20. A tight, spherical collection of as many as several hundred thousand stars is a
a) Galaxy, b) globular cluster, c) open cluster, d) Einstein's cluster
21. When Galaxies collide
a) their stars collide to form larger stars, b) both galaxies crumple into very dense systems
c) they simply perturb each other’s shape, d) no galaxies are left after the collision
22. An Einstein ring is a
a) group of galaxies which forms a ring in inter-galactic space
b) something Al gave to his mother
c) the theory that say the universe is a continuous ring of space time
d) distortion of an image due to gravitational effects
23. Why is the energy source of active galaxies thought to be extremely compact?
a) Their energy is totally no stellar in origin.
b) Their spectra are like those produced by ordinary stars.
c) They vary on rapid time scales.
d) They can be seen clearly; we can see that the energy source is compact.
24. As matter streams into a black hole it usually forms what kind of structure
a) accretion disk, b) spherical shell, c) a dark nebula, d) star formation region
25. The very rapid orbital speed detected near the center of our galaxy suggests that
a) our galaxy has a lot of stored angular momentum, b) massive stars are at the center
c) a black hole is at the center, d) we have been in a collision in the past
26. What causes Cepheid variables to vary in brightness?
a) they pulsate, b) eclipses,
c) changes in nuclear energy generation rate, d) obscuration by clouds of dust
27. Quasars were originally discovered as
a) strong radio sources identified with star-like images on photographs
b) variable sources of light
c) bright galaxies, and only later found to be radio sources
d) the only type of radio source within our galaxy
28. Which type of galaxy contains the least amount of interstellar material?
a) Ellipticals, b) spirals, c) barred spirals, d) irregulars
29. Quasars may be caused by
a) directly viewing jets of material from black holes, b) interacting galaxies
c) massive super-nova explosions, d) left over fragments of the big bang explosion
30. What observation of the Galaxy suggests it is much larger than the halo and contains a large amount of matter not in the form of stars?
a) The rotation curve, b) Motions of the globular clusters
c) The shape of the spiral arms, d) Infrared observations of the center of the Galaxy
31. We cannot see the other side of the galaxy primarily because our view is blocked by
a) too many stars, b) glowing interstellar gas, c) interstellar dust, d) planetary nebulae
32. A primary difference between spiral and elliptical galaxies is
a) all ellipticals are more massive than spirals
b) ellipticals have more extensive interstellar media than spirals
c) star formation has ceased in ellipticals, but not in spirals
d) spirals have more stars than ellipticals
33. How do we know that the quasars are at large distances?
a) they are extremely dim, b) they have large redshifts,
c) they have large parallaxes, d) they are greatly obscured by interstellar dust
34. Why do the cores of spiral galaxies appear redder than the arms
a) because of reddening due to dust, b) because the cores are bigger
b) because the cores are further away, d) because of black holes in the center
35. What is hardest to explain about spiral arm structure
a) that they ever existed in the first place, b) why galaxies only have two of them
c) why they have sharp boundaries, d) how they maintain themselves
36. Irregular galaxies have ill defined shape because
a) they rotate too slow to form a disk, b) active star formation disrupts disk
c) too many black holes distort space time, d) recent collisions caused loss of shape
37. What kind of galaxy do we live in?
a) Spiral, b) elliptical, c) spherical, d) irregular
38. The distribution of galaxies in the universe
a) follows the same distribution as stars, b) arraigned on the surfaces of giant bubbles or voids
c) fairly uniform, d) has remained the same as it was during the big bang
39. From the Sun, what is the distance to the Galaxy's center?
a) 8 kpc, b) 30 kpc, c) 300 pc, d) 1000 Ly.
40. The Hubble classification scheme for galaxies:
a) accurately predicts galaxy evolution, b) is not very useful
c) has helped advance the study of galaxies, d) explains why quasars are not seen close to us