Astro 115 Spring 2000 Homework #6 Due May 18, 2000
Choose the BEST answers. Turn in your answers on a scantron.
NOTE: There are a few problems where more than one answer are correct. Bubble in ALL the answers that apply.
Hint: The questions are broken up in chapters and are in order.
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. _____________ 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 Glennd. Carl Sagan
e. Annie Cannon
3. 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.
4. The Milky Way contains how many stars and has a mass of at least how many solar masses?
a. 200 billion, 100 billion b. 200 billion, 200 billion
c. 200 trillion, 200 billion d. unknown
5. The sun is moving how fast and in the direction of which constellation?
a. 220 km/sec, Cygnus b. 8 km/sec, Cygnus
c. 220 km/sec, Sagittarius d. 8 km/sec, Sagittarius
6. The age of the Milky Way galaxy has been estimated to be at least 15 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*.
7. 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.
8. Population II stars (choose all that apply)
a. are primarily found in the disk of the galaxy.
b. contain more heavy metals than population I stars.
c. are primarily old low mass stars.
d. are located in globular clusters
9. 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.
10. The orbits of population I stars (choose ALL that apply)
a. are confined to disk of the galaxy. b. are very elliptical.
c. are nearly circular.
d. are randomly inclined to the disk of the galaxy.
11. Sgr A* is believed to be the center of the Milky Way galaxy because (choose ALL that apply)
a. It lies in the general direction of the center of the galaxy based on observations of globular clusters.
b. It is located near the galactic corona.
c. It is easily visible with optical telescopes and has the appearance of a massive black hole.
d. It does not move with respect to the rest of the galaxy.
*Chapter 13*
12. The Milky Way is what kind of galaxy?
a. Spiral b. Barred Spiral c. Elliptical d. Irregular
13. 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.
14. 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.
15. An irregular 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.
16. 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.
17. 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.
18. 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.
e. contained in the disk of the galaxy.
19. 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
20. The look-back time is
a. how long the light from an object takes to reach Earth.
b. numerically equal to the distance in light-years.
c. smaller for more distant objects.
d. all of these
e. Both how long the light from an object takes to reach Earth, and numerically equal to the distance in light-years.
21. 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.
22. 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.
23. How many galaxies are in the Local Group?
a. few dozen b. few hundred c. few thousand d. billions
24. 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.
*Chapter 15*
25. The Hubble law is a relation between distance and the radial velocity of recession which implies that the Universe is expanding. Thus, the further away a galaxy is from Earth, the greater its _____________.
a. red shift b. mass c. luminosity d. diameter
26. If H equals 50 km/sec/Mpc, then a galaxy with a radial velocity of 2000 km/sec probably has a distance of
a. 2050 Mpc b. 1950 Mpc c. 40 Mpc d. 0.025 Mpc
e. 100,000 Mpc
27. The resolution of Olbers' paradox suggests that it gets dark at night because
a. the universe is not infinite in age.
b. the universe is not static.
c. the universe is closed.
d. Both the universe is not infinite in age, and the universe is not static.
e. all of these
28. The assumption of universality states that
a. the universe looks the same at all epochs.
b. the universe looks the same from all locations over sufficiently great distances.
c. the universe looks the same in all directions over sufficiently great distances.
d. the physical laws we observe on Earth apply everywhere in the universe.
e. all of these
29. The assumption of isotropy states that
a. the universe looks the same at all epochs.
b. the universe looks the same from all locations over sufficiently great distances.
c. the universe looks the same in all directions over sufficiently great distances.
d. all of the above e. none of these.
30. If galaxy A is four times more distant than galaxy B, then according to the Hubble Law, galaxy A will recede ___________ than galaxy B.
a. 16 times faster b. 4 times faster
c. 2 times faster d. 1.2 times faster e. 0.25 times faster
31. The universe is said to be closed if (choose ALL that apply)
a. gravity is strong enough to stop the expansion in a finite time.
b. the density of the universe is less than the critical density.
c. the universe is finite. d. none of these
32. If the Hubble constant, H, is larger at great distances, then the
a. universe must be older than we suspect.
b. matter in the universe is not important to its motion.
c. expansion is slowing.d. all of the above e. none of these
33. What was the temperature of the universe when the recombination took place that produced the cosmic background radiation we observe today?
a. about 2.7 K b. about 300 K c. about 3000 K
d. about 3 million K e. about 3 billion K
34. Measured ages of globular clusters and a study of the time required for massive stars to build up the present abundance of heavy elements suggests that the universe is
a. no more than 20 billion years old.
b. no more than 10 billion years old
c. at least 14 billion years old
d. flat e. closed
35. The cosmic background radiation comes from a time in the evolution of the universe
a. when protons and neutrons were first formed.
b. when the big bang first began to expand.
c. the inflationary period
d. when gamma rays had enough energy to destroy nuclei
e. when electrons began to recombine with nuclei to form atoms.
36. The flatness problem and horizon problem
a. are solved if there was a sudden inflation of the universe at time before recombination occurred.
b. show that the universe cannot be described by the steady state theory.
c. show that dark matter must be a small fraction of the total mass of the universe.
d. imply that the universe was once much hotter than it is now.
e. imply that the inflationary theory is incorrect.
37. Galaxy seeds around which galaxies, clusters and walls grew may have been
a. caused by hot dark matter. b. caused by baryons.
c. the result of the separation of the electromagnetic and weak forces.
d. the result of freezing water molecules shortly after the universe became transparent to photons.
e. caused by defects in space-time.
38. Whether the universe is open, closed or flat depends on the ________ of the universe.
a. luminosity b. density c. temperature
d. radius e. rotation rate
39. The age of the universe can be determined if
a. the universe is flat.
b. the amount of dark matter in the universe can be accurately determined.
c. the rate of recession of the galaxies in the Local Group can be accurately determined.
d. the temperature of the cosmic background radiation can be accurately determined.
e. the Hubble constant and density of the universe can be accurately determined.
*Chapter 20*
40. A cells DNA molecules are constructed of
a. amino acids. b. proteins.
c. sugars, phosphates, and bases.
d. all of the above e. none of these
41. DNA molecules contain patterns for the production of
a. proteins. b. amino acids.
c. phosphates and sugars. d. fours kinds of bases.
e. all of these
42. The first complex life appeared on Earth about 0.5 billion years ago during the
a. Jurassic Period. b. Mississippian Period.
c. Cambrian Period. d. Precambrian Period. e. Neolithic Period.
43. The Miller experiment created
a. life. b. artificial proteins. c. DNA.
d. simple molds. e. amino acids.
44. ________ is the molecule within a cell that actually assembles proteins from amino acids.
a. An enzyme b. The nucleus c. RNA d. ALH84001
e. PAH
45. The stars most likely to have inhabited planets are
a. G to K main sequence stars. b. B to A main sequence stars.
c. G to K giants. d. M main sequence stars.
e. white dwarfs and neutron stars.
46. The life zone is
a. the region on a planet where conditions are acceptable for life to exist.
b. a region around a star where a planet's temperature would permit the existence of liquid water.
c. very small for a massive star.
d. only found around G and K stars.
e. a region on a young planet where amino acids can begin to form DNA molecules.
47. Life on Earth is based on
a. carbon chemistry. b. helium chemistry.
c. silicon chemistry. d. oxygen chemistry.
e. nitrogen chemistry.
48. What limitation(s) make it impossible to travel between stars?
a. Fuel requirements
b. The tremendous distances between stars
c. The finite speed at which objects can travel d. none
49. Why is it believed that life can not evolve on a planet that orbits a spectral type A, B or O star?
a. These stars produce too much infrared radiation which would destroy carbon-based organisms.
b. These stars have very small life zones.
c. These stars are not capable of producing planets.
d. These stars do not remain on the main sequence long enough for life to evolve.
e. These stars take too long to form.
50. The number of communicative civilizations in our galaxy is limited by
a. the size of the average planet. b. the survival of technological societies.
c. 21-cm radiation. d. their distance from Earth.
e. the number of high mass stars in the galaxy.