The Milky Way

1. The general shape of our galaxy is nearest to that of a

a. pear

b. egg

c. ball

d. fried egg.*

2. Cepheid variable stars are important to astronomy primarily because they allow us to determine stellar

a. distance*

b. mass

c. temperature

d. pulsation period

e. chemical composition.

3. An important relation observed for Cepheid variables is that between

a. mass and luminosity

b. luminosity and temperature

c. period and luminosity*

d. period and radius

e. mass and temperature.

4. The resolution of the nature of the "nebulae" came from the discovery of ______ within the "nebulae".

a. solar-type stars

b. T-Tauri stars

c. RR Lyrae stars

d. Cepheid variables*

e. planetary nebulae.

5. The solar system is located within

a. the galactic halo

b. the galactic disc*

c. the galactic nucleus

d. none of the above; the solar system is not located within a galaxy.

6. Our ability to detect distant stars in our galaxy is limited because of

a. absorption by dust in the galaxy*

b. the existence of strong 21-cm radiation in the galaxy

c. the existence of many bright nebulae in the galaxy

d. none of the above; there is no limit in our ability to detect distant stars.

7. 21-cm radiation is important to astronomy because

a. the interstellar medium is opaque at 21 cm

b. the interstellar medium is transparent at 21-cm*

c. stars emit strongly at 21-cm, thus allowing them to be seen at large distances

d. nebulae emit strongly at 21-cm

e. black holes emit large amounts of radio radiation at 21-cm.

8. The mass of the Milky Way galaxy is most easily determined from

a. application of Newton's second law

b. Kepler's third law as modified by Newton*

c. 21-cm radiation

d. spectral analysis of Cepheid variables

e. Doppler shift measurements of the galactic nucleus.

9. The nucleus of the Milky Way galaxy is composed primarily of

a. young, hot stars

b. old, cool stars*

c. hydrogen gas

d. planetary nebulae

e. solar-type stars.

10. The energy source at the center of our galaxy

a. is not visible at optical wavelengths.

b. produces X rays.

c. must be less than 10 AU in diameter.

d. all of the above*

e. none of the above.

11. Which one of the following features does not exist in the H-R diagram of a typical globular cluster?

a. red giant branch

b. lower main sequence of cool stars

c. upper main sequence of hot stars*

d. horizontal branch.

12. Which one of the following is taken as evidence for a possible black hole in the centers of some globular clusters?

a. observations of x-ray bursts*

b. these clusters have high masses

c. the centers of some globular clusters are dark

d. clusters are composed of old, dead stars most of which are black holes

e. theoretical calculations predict the existence of black holes in the cluster center.

13. Emission nebulae glow visibly because

a. light from cool stars in the vicinity is reflected by the gas

b. 21-cm radiation is absorbed from background stars

c. nearby hot stars ionize the gas which radiates when ions recombine with electrons*

d. of all the above.

14. Emission nebulae appear red on photographs because

a. they are excited by red stars

b. the light from red stars is reflected by the gas

c. they emit 21-cm radiation which is red radiation

d. hydrogen emits strongly in the red.*

15. The visible disk of the Milky Way galaxy has a radius of about

a. 1500 pc.

b. 15000 pc.*

c. 150000 pc.

d. 1500000 pc.

e. None of these.

16. Absorption nebulae are

a. Nebulae that shine by starlight reflected off dust grains.

b. Heated, glowing clouds of gas.

c. H II regions.

d. Supernova remnants.

e. None of these.*

17. Emission nebulae are

a. Nebulae that shine by starlight reflected off dust grains.

b. Heated, glowing clouds of gas.*

c. H II regions.

d. Supernova remnants.

e. None of these.

18. A red nebula surrounds a blue star. This nebula is

a. An absorption nebula.

b. An emission nebula.*

c. A reflection nebula.

d. All of these.

e. None of these.

19. The first stars to form in our galaxy

a. had circular orbits.

b. had highly elliptical orbits.*

c. were population I stars.

d. all had orbits in the same plane.

e. formed the galactic clusters we see today.

20. Compared with the Sun, which one of the following statements is true?

a. stars in the halo are deficient in heavy elements*

b. stars in the galactic disk are deficient in heavy elements

c. stars in the nucleus have large amounts of heavy elements

d. all chemical elements are distributed more or less uniformly throughout all parts of the galaxy.

21. The observed distribution of globular clusters indicates that the gas cloud from which the galaxy formed was

a. disk-shaped

b. spherical*

c. elliptical.

22. The disk-like shape of the Milky Way galaxy provides evidence that the early galaxy

a. was a strong x-ray emitter

b. had a high temperature

c. had a strong magnetic field

d. rotated*

e. had a high abundance of heavy elements.

23. The differences between Population I and II stars are

a. Pop. I stars have low metal abundance and highly elliptical orbits

b. Pop. I stars have low metal abundance and Pop. II stars have high metal abundance

c. Pop. II stars have low metal abundance and highly elliptical orbits*

d. Pop. I stars are older than Pop. II stars.

24. The chemical abundance of population I stars

a. indicates that they were formed before the population II stars.

b. indicates that the material they formed from had been enriched with material from supernovae. *

c. indicates that they contain very few heavy metals compared to halo stars.

d. depends on the temperature of the star.

e. depends on the mass of the star.

25. Younger stars have more heavy elements because

a. old stars destroy heavy elements as they age.

b. young stars burn their nuclear fuels faster.

c. the heavy elements were made in previous generations of stars. *

d. heavy elements haven't had time to settle to the core of these younger stars.

e. all of these

26. Spiral arms appear to be prominent in spiral galaxies because

a. all the stars and distributed in a spiral pattern

b. cool stars are distributed in a spiral pattern while the hot stars are spread more uniformly

c. hot stars are distributed in a spiral pattern while the cool stars are spread more uniformly*

d. globular clusters are distributed in a spiral pattern around the galaxy.

27. One problem faced by astronomers in trying to figure out the structure of the Milky Way galaxy is that

a. there is no way to measure distances greater than about 12,000 ly

b. the Milky Way galaxy looks the same in all directions from Earth

c. we can only see a small region of the Milky Way galaxy with optical telescopes because of interstellar dust *

d. the Milky Way galaxy is always changing, so it's hard to pin down a single picture

28. The distribution of B stars in the galactic plane shows a spiral arm pattern because

a. such luminous objects do not live long enough to move out of the arms*

b. their great masses do not let them overcome the attraction of the arms

c. they continue to accumulate new material from the clouds in the arms

d. none of the above; the distribution of stars does not show a spiral pattern.

29. Radio maps of our galaxy show spiral arms because

a. the arms have larger Doppler shifts.

b. the gas in the spiral arms is very hot.

c. the dust in spiral arms is denser.

d. the gas in spiral arms is denser.*

e. the stars in the spiral arms emit most of their energy at radio wavelengths.

30. Which of the following do astronomers NOT use to map the spiral structure of the Milky Way galaxy?

a. cool K- and M-stars *

b. hot O- and B-stars

c. 21-cm line from neutral hydrogen

d. H II regions

31. The Sun's orbit around the Milky Way galaxy

a. is a random orbit, much like those of the globular clusters

b. is nearly a circular orbit lying in the plane of the Milky Way galaxy's disk *

c. follows along one of the spiral arms

d. slowly moves toward the galactic center as the spiral arms wind tighter around the nucleus

32. As evidenced by the concentration of gas and dust in the spiral arms, a density wave has its strongest effect on

a. stars

b. gas and dust*

c. star clusters

d. binary stars

e. other nearby galaxies.

33. Our galaxy is suspected to be surrounded by a galactic corona because the disk of the galaxy

a. rotates faster than expected in its outer region. *

b. rotates more slowly than expected in its outer region.

c. rotates faster than expected in its inner region.

d. rotates more slowly than expected in its inner region.

e. is much flatter than expected.

34. The galactic corona is believed to contain mostly

a. O and B stars.

b. G, K, and M stars.

c. open clusters

d. globular clusters

e. dark matter.*