____ 1. Who First Calibrated the Cepheid Variable Stars for Use in Determining Distance?

Galaxies-Test1

Multiple Choice

Identify the letter of the choice that best completes the statement or answers the question.

____ 1. Who first calibrated the Cepheid variable stars for use in determining distance?

a. / Henrietta Leavitt
b. / Edwin Hubble
c. / John Glenn
d. / Carl Sagan
e. / Harlow Shapley

____ 2. 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
e. / star formation regions

____ 3. A group of 10 to 100 stars that formed at the same time but are so widely scattered in space their mutual gravity cannot hold them together is called

a. / a globular cluster.
b. / an open cluster.
c. / an association.
d. / a spherical component
e. / an accretion disk.

____ 4. 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.

____ 5. 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

____ 6. 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.

____ 7. Good spiral tracers are all

I. / very old.
II. / very young.
III. / very luminous.
IV. / moving with large radial velocities.
a. / I & III
b. / I & IV
c. / II & III
d. / II & IV
e. / I, III, & IV

____ 8. 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.

____ 9. If the spiral density wave were the only thing producing spiral arms, it would be expected that

a. / all spiral arms would be dust free.
b. / all galaxies would have only two smooth spiral arms.
c. / the Milky Way would be more massive than observed.
d. / the Milky Way wouldn't have any spiral arms.
e. / the halo component of the Milky Way would show spiral arms as well.

____ 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. ______first noticed that for Cepheid variable stars, there was a direct relation between the luminosity and the period of the variation in their brightness.

a. / Henrietta Leavitt
b. / Edwin Hubble
c. / John Glenn
d. / Carl Sagan
e. / Annie Cannon

____ 12. Population II stars

I. / are primarily found in the disk of the galaxy.
II. / contain more heavy metals than population I stars.
III. / are primarily old low mass stars.
IV. / are located in globular clusters.
a. / III & IV
b. / I & II
c. / II
d. / IV
e. / I, II, & III

____ 13. The age of the Milky Way galaxy has been estimated to be at least 13 billion years based on

a. / observations of globular clusters.
b. / observations of open clusters.
c. / 21-cm radiation from H I regions.
d. / the rotation curve of the galaxy.
e. / the energy produced by Sagittarius A*.

____ 14. CO observations of the galaxy reveal

a. / the location of dense neutral hydrogen clouds.
b. / the location of population II stars.
c. / the location of population I stars.
d. / the location of the galactic corona.
e. / the location of giant molecular clouds.

____ 15. 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.

____ 16. The center of our galaxy lies in the direction of the constellation of

a. / Ursa Minor.
b. / Ursa Major.
c. / Sagittarius.
d. / Orion.
e. / Monoceros.

____ 17. Nucleosynthesis

a. / is the process by which energy is produced at the center of the galaxy.
b. / is the process by which hydrogen and helium are converted into heavier elements.
c. / describes the structure of a globular cluster.
d. / describes how the magnetic field of the galaxy traps cosmic rays.
e. / describes the method by which neutral hydrogen produces 21 cm radiation.

____ 18. The nuclear bulge of our galaxy

a. / contains stars that are primarily population I stars.
b. / contains relatively large amounts of gas and dust.
c. / contains stars primarily associated with the spherical component of our galaxy.
d. / contains stars primarily associated with the disk component of our galaxy.
e. / a, b, and d

____ 19. The orbits of population I stars

I. / are confined to disk of the galaxy.
II. / are very elliptical.
III. / are nearly circular.
IV. / are randomly inclined to the disk of the galaxy.
a. / I
b. / IV
c. / I & IV
d. / II & IV
e. / I & III

____ 20. The traditional theory states that the galaxy formed

a. / as a large spherical cloud of gas that was rotating very slowly.
b. / from a large cloud of material that broke off a larger galaxy.
c. / from material that had been ejected in the violent explosion of a dying galaxy.
d. / as a result of mergers between several smaller groups of gas, dust, and stars.
e. / as two massive galaxies collided.

____ 21. The traditional theory of the formation of our galaxy cannot explain

a. / the existence of the disk of the galaxy
b. / the fact that the oldest stars in the galaxy are not metal free.
c. / the spherical distribution of the globular clusters
d. / the difference in metal abundance of the population I and II stars.
e. / the existence of the nuclear bulge.

____ 22. Radio maps of the spiral arms of our galaxy

a. / reveal that our galaxy is a grand design spiral.
b. / map the location of Hot O and B stars by the radio radiation they emit.
c. / reveal that the spiral arms are winding up and growing closer together.
d. / reveal that the sun is currently located in the center of a spiral arm.
e. / map the location of dense neutral hydrogen clouds.

____ 23. Sgr A* is believed to be the center of the Milky Way galaxy because

I. / It lies in the general direction of the center of the galaxy based on observations of globular clusters.
II. / It is located near the galactic corona.
III. / It is easily visible with optical telescopes and has the appearance of a massive black hole.
IV. / It does not move with respect to the rest of the galaxy.
a. / I & II
b. / II & III
c. / I & IV
d. / II & IV
e. / I, III, & IV

Figure 12-1

____ 24. See Figure 12-1 above. A Type II Cepheid has been located in a distant globular cluster with a period of 10 days. What is the star's absolute magnitude?

a. / -1
b. / 0
c. / -4
d. / -6
e. / The absolute magnitude of a Cepheid variable cannot be determined unless its distance is known.

____ 25. See Figure 12-1 above. A Type I Cepheid has been located in an open cluster. The period of the Cepheid variable is 30 days and the variables apparent visual magnitude is 10. What is the distance to this open cluster?

a. / 100 pc
b. / 10,000 pc
c. / 20 pc
d. / 300 pc
e. / 2500 pc

____ 26. An E galaxy contains

a. / mostly lower-main sequence stars and giants.
b. / mostly upper main sequence stars and giants.
c. / mostly upper main sequence stars and gas and dust.
d. / roughly equal numbers of upper and lower main sequence stars.
e. / mostly white dwarfs and supergiants.

____ 27. An spiral galaxy contains

a. / mostly lower-main sequence stars and giants.
b. / mostly upper main sequence stars and giants.
c. / mostly upper main sequence stars and gas and dust.
d. / upper and lower main sequence stars and gas and dust.
e. / mostly white dwarfs and supergiants.

____ 28. An irregular galaxy contains mostly

a. / lower-main sequence stars and giants.
b. / upper main sequence stars and giants.
c. / upper main sequence stars and gas and dust.
d. / upper and lower main sequence stars and gas and dust.
e. / white dwarfs and supergiants.

____ 29. A megaparsec is equivalent to

a. / 3.26 light-years.
b. / 206,265 light years.
c. / 206,265 AU.
d. / 3,260,000 light-years.
e. / the diameter of the Milky Way galaxy.

____ 30. Which of the following is not used as a distance indicator?

a. / large globular clusters
b. / Herbig-Haro objects
c. / H II regions
d. / Cepheid variable stars
e. / Supernovae

____ 31. The look-back time is

a. / the time it takes for the light from an object to reach Earth.
b. / numerically equal to the distance in light-years.
c. / smaller for more distant objects.
d. / all of the above
e. / a and b above

____ 32. 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 methods.
e. / none of these methods.

____ 33. Most of the mass of a galaxy is contained in the

a. / massive O and B stars in the galaxy.
b. / H I regions of the galaxy.
c. / H II regions of the galaxy.
d. / dark matter of the galaxy.
e. / disk of the galaxy.

____ 34. Galactic cannibalism refers to

a. / binary galaxies.
b. / the merging of galaxies.
c. / galaxies drawing in gas from the intergalactic medium.
d. / the destruction of a galaxies globular clusters by the galaxies nucleus.
e. / none of these

____ 35. Astronomers now speculate that a galaxy's shape depends on all of the following except

a. / the rate of star formation.
b. / the history of past collisions.
c. / the mass.
d. / the chemical composition.
e. / All of these are important in determining a galaxy's shape.

____ 36. Based on the galaxies found in the Local Group of galaxies, the most common type of galaxy in the universe is expected to be

a. / the spiral galaxies.
b. / the barred spiral galaxies.
c. / the dwarf elliptical galaxies.
d. / the irregular galaxies.
e. / the giant elliptical galaxies.

____ 37. We should expect galaxies to collide fairly often because

a. / they are large with respect to their separation distances.
b. / galaxies contain large amounts of neutral hydrogen.
c. / galaxies occur in clusters.
d. / a and c
e. / none of the above

____ 38. ______galaxies contain large clouds of gas and dust, both young and old stars, but have no obvious spiral arms or nucleus.

a. / Irregular
b. / S0
c. / E7
d. / Sa
e. / E0

____ 39. ______is an irregular galaxy that is believed to have collided with the Milky Way and is expected to merge with the Milky Way in the future.

a. / The Andromeda galaxy
b. / The Small Magellanic Cloud
c. / M87
d. / The Virgo cluster
e. / The Whirlpool galaxy

____ 40. The rotation curve of a galaxy can be used to determine

a. / the relative number of hot young stars in the galaxy.
b. / the relative amount of gas and dust in the galaxy.
c. / the radius of the galaxy.
d. / the luminosity of the galaxy.
e. / the mass of the galaxy.

____ 41. The Milky Way galaxy is part of

a. / the Virgo cluster.
b. / the Large Magellanic Cloud.
c. / the Small Magellanic Cloud.
d. / the Local Group.
e. / a rich cluster.

____ 42. It is believed that ring galaxies form

a. / when two galaxies collide nearly head on at high speed.
b. / when two spiral galaxies collide, but not directly head on.
c. / from a large cloud of gas and dust with very little angular momentum.
d. / from a large cloud of gas and dust with a very high angular momentum.
e. / when more than two galaxies collide at the same time.

____ 43. Observations of galaxies and clusters of galaxies indicate that about ______per cent of the universe is dark matter.

a. / 5
b. / 25
c. / 50
d. / 75
e. / 95

____ 44. Starburst galaxies

a. / contain a large number of very young stars, but very little evidence of gas clouds.
b. / contain a large number of very old stars and almost no gas or dust.
c. / are often associated with a galaxy that is colliding with another galaxy.
d. / are common in rich clusters.
e. / are composed of filaments and voids.

____ 45. An elliptical galaxy could

a. / evolve into an irregular galaxy when it has used up all of its gas and dust.
b. / be formed from the collision and merger of spiral galaxies.
c. / evolve from a single spiral galaxy when the spiral has used up all of its gas and dust.
d. / become a starburst galaxy if it were to move through the hot intergalactic medium of a cluster.
e. / evolve from an S0 galaxy if the S0 galaxy were to increase its rotation rate.

____ 46. The Virgo cluster

a. / is the galactic cluster that contains the Milky Way
b. / is the oldest known cluster of galaxies.
c. / is located at the center of the universe.
d. / contains mostly spiral galaxies and very few elliptical galaxies.
e. / is a rich cluster and the closest cluster of galaxies outside of the Local Group.

____ 47. Supermassive black holes are believed to be located at the center of many galaxies because