Reference no: EM131128121

1. If Hubble's constant is 75 km/s/Mpc, then the age of the universe is 13 billion years. Suppose it were discovered that Hubble's constant is actually larger than 75 km/s/Mpc. What effect would this fact have on the calculated age of the universe?

A. The calculated age would be increased.

B. The calculated age could be increased or decreased, depending on the recession velocity of the galaxy being investigated.

C. The calculated age would be decreased.

D. The calculated age would be the same.

2. What condition is necessary for the universe to be closed?

A. The cosmological constant must be large.

B. The density of the universe must be large.

C. The universe must have no mass in it.

D. The density of the universe must be small.

3. How does the diameter of a black hole (size of the event horizon) depend on the mass inside the black hole?

A. The diameter does not depend on the mass.

B. The greater the mass, the greater is the diameter-until the mass becomes relatively large and then the diameter decreases with increasing mass.

C. The greater the mass, the greater is the diameter.

D. The greater the mass, the smaller is the diameter.

4. A star ascending the red-giant branch for the second time in the asymptotic giant branch phase will have

A. no fusion reactions; the star has used up all its nuclear fuel.

B. no nuclear reactions in the core, but a helium-fusion shell outside the core, which itself is surrounded by a shell of hydrogen.

C. hydrogen-fusion reactions occurring in the core.

D. no nuclear reactions occurring in the core but hydrogen fusion in a shell outside the core.

5. What was the implication of the observation by Edwin Hubble that the Cepheid variable stars he measured in the Andromeda "nebula" appeared to be very faint compared with what was expected?

A. Hubble had discovered a new class of intrinsically faint Cepheid variable stars.

B. The Andromeda "nebula" was very far away and was in fact a galaxy.

C. Dust and gas in the "nebula" had severely reduced the light from these stars.

D. The observed period was affected by the intense gravitational field of the "nebula" as predicted by general relativity, leading to incorrect luminosity determination.

6. What would you expect to be the overall color of a globular cluster of stars? Explain.

A. blue, because of the scattering of starlight from the dust surrounding the stars in the cluster

B. red, because of the older population of stars in the cluster

C. red, because of the emission of light by the hydrogen gas in H II regions surrounding the stars in the cluster

D. blue, because of the contribution from young and very hot stars in the cluster

7. A clock with a luminous dial is moving toward you at a speed that is a large fraction of the speed of light. Which of the following will you observe?

A. The light emitted by the clock will be shifted toward longer wavelengths compared to those seen by an observer moving with the clock.

B. The light from the clock is approaching you at speed c.

C. The clock runs fast compared to an identical clock at rest in your hand.

D. The clock appears thicker, front to back, than the identical clock in your hand.

8. A planetary nebula is created

A. in hours or less, during the explosion of a massive star.

B. over several hundred years, during mass transfer in a close binary star system.

C. in seconds, during the helium flash in a low-mass star.

D. over a few thousand years or more, in a slow expansion away from a low-mass star, driven by a series of thermal pulses from helium fusion.

9. Which of the following statements correctly describes the rotation of the Milky Way Galaxy?

A. Objects in the disk have random orbits with no net rotation of the disk about the center of the Galaxy, and the halo rotates differentially (objects farther from the center take longer to complete an orbit than objects closer to the center).

B. The disk rotates differentially (objects farther from the center take longer to complete an orbit than do objects closer to the center), and the halo objects have random orbits with no net rotation of the halo about the center of the Galaxy.

C. The disk rotates like a solid object (objects at all distances take the same time to complete an orbit), and the halo objects have random orbits with no net rotation of the halo about the center of the Galaxy.

D. The disk rotates differentially (objects farther from the center take longer to complete an orbit than objects closer to the center), and the halo rotates differentially (objects farther from the center take longer to complete an orbit than objects closer to the center).

10. Harlow Shapley first located the center of the Milky Way Galaxy in 1917 by

A. observing the distribution of globular clusters in the galactic halo.

B. measuring the positions of supernova explosions throughout the Galaxy.

C. observing the distribution of hydrogen gas, measured by 21-cm radio emission.

D. measuring redshifts of stars in the galactic plane and disk.

11. What is believed to be the maximum mass for a neutron star?

A. 1.4 solar mass

B. 150 solar masses

C. 12 solar masses

D. 3 solar masses

12. Matter in an accretion disk is in orbit around a black hole, but friction within the disk causes the matter to gradually spiral into the black hole. What will change in terms of the observable properties of the black hole as this process continues?

A. Both the mass and the angular momentum of the black hole will increase.

B. Nothing will change.

C. Only the mass will increase.

D. The mass, the angular momentum, and the rate of evaporation of the black hole will increase.

13. The solar mass of the star that exploded to form supernova SN 1987A was probably about

A. 20.

B. 1.4.

C. less than 1.

D. 40.

14. Suppose we could examine a star and determine its absolute magnitude M without any intervening gas and dust. Compared to its absolute magnitude measured with gas and dust between us and the star, this "clean" measurement of M would be

A. a larger number.

B. a smaller number.

C. either larger or smaller depending on the star's speed (toward or away).

D. the same number.

15. How many properties of the matter inside a black hole can be measured from outside the black hole?

A. 6

B. 3

C. 4

D. only 1

16. "Starquakes" are the rearrangement of material in a neutron star, similar to an earthquake here on Earth. Which one of the following statements about starquakes is correct?

A. Starquakes are caused by stresses in the crusts of magnetars due to their enormous magnetic fields.

B. Starquakes cause rents in the crust of a neutron star and allow gamma rays and X rays to escape from the interior, like the coronal holes in the Sun's atmosphere.

C. Starquakes are the cause of the gradual increase in the period in pulsar signals.

D. Starquakes are caused by stresses in the crusts of neutron stars that form close binary systems and exert tremendous forces on each other.

17. A T Tauri star is at what stage of its stellar evolution?

A. well established on the main sequence

B. the end of its life, decaying away and cooling

C. protostar, before the main-sequence phase

D. just before red giant phase, when variability begins

18. What is the distance from the center to the event horizon of a nonrotating black hole with the mass of Earth?

A. 6 km

B. 9 mm

C. 1.5 m

D. 8.5 × 10^-7 m

19. In the H-R diagram shown in Figure 12-31b of Discovering the Universe, 10th ed., the brightest stars in the Pleiades cluster are not on the main sequence but away from it toward the upper right. Explain.

A. The brightest stars have not yet reached the main sequence and are in the T Tauri phase.

B. These blue supergiant stars have already begun to evolve toward the red supergiant phase.

C. The brightest stars have already evolved through the red giant phase and have now returned to the blue giant phase on their way to the white dwarf phase.

D. The brightest stars have already become white dwarf stars, as shown by their position.

20. Which of the following statements is not a characteristic of elliptical galaxies?

A. Different elliptical galaxies appear to be flattened by different amounts.

B. Almost all star formation stopped in elliptical galaxies billions of years ago.

C. Elliptical galaxies are almost devoid of interstellar gas and dust.

D. Elliptical galaxies have a disk and a central bulge but no spiral arms.

21. When the Sun entered the main sequence, its core was approximately 75% hydrogen and 25% helium, by mass. What was the ratio of hydrogen nuclei to helium nuclei?

A. 3:1

B. 16:1

C. 12:1

D. 4:1

22. How much time does it take for a 1-solar-mass protostar to finish accreting mass from the interstellar cloud?

A. 100,000 years

B. 1 billion years

C. 10 million years

D. 10,000 years

23. "It is starlike in appearance, showing very high redshift and an energy output of at least 100 galaxies from a small region about 1 ly across." These characteristics describe which of the following astronomical objects?

A. quasar

B. center of the Milky Way Galaxy

C. red supergiant star

D. supernova explosion in a neighboring galaxy

24. In the 1970s it was discovered that, among spiral galaxies, the wider the 21-cm radio emission line, the brighter is the galaxy. What is the name of this relation?

A. Hubble law

B. Hawking effect

C. Tully-Fisher relation

D. mass-luminosity law

25. The escape velocity for material inside a black hole is

A. greater than the speed of light.

B. twice that from a neutron star.

C. infinite.

D. zero.

26. What percentage of all matter ejected into the interstellar medium in the Milky Way Galaxy each year by stars is contributed by planetary nebulae?

A. almost 100%

B. about 50%

C. less than 1%

D. between 10 and 20%

27. Measurements from distant galaxies indicate that supernovae should occur at a rate of five per century in a spiral galaxy such as the Milky Way, but only three have been recorded in this Galaxy in the past 1000 years. Explain.

A. The majority of supernovae must have occurred in the plane of the Milky Way and hence were hidden from Earth by the dense gas and dust in the Milky Way plane.

B. Most supernovae produce X rays and radio waves, not visible light, and were hence invisible to earlier observers.

C. Observers were not watching the sky carefully enough, particularly through the Dark Ages and over the past few centuries.

D. The Milky Way Galaxy is somehow different, with much lower numbers of very massive stars in general, so many fewer stars have undergone supernova explosions.

28. Where are emission nebulae (H II regions) found?

A. in or near old open clusters

B. around hot stars

C. in globular star clusters

D. around low-mass stars

29. What kind of curvature (geometry of space) does the universe have if the universe is just on the boundary between being open and being closed?

A. spherical

B. parabolic

C. hyperbolic

D. flat

30. Which of the following statements correctly describes cosmic censorship?

A. The amount of mass in a black hole can never be measured.

B. All properties of the matter inside a black hole are hidden by the event horizon, except for the total mass of the matter.

C. Black holes cannot have magnetic fields.

D. Nothing can leave a local region of space that contains a singularity.

31. In which direction(s) are the jets of matter ejected from a supermassive black hole to produce the many effects surrounding quasars and active galaxies?

A. They are tangential to the accretion disk in two opposite directions, 180° apart; the matter is spun off by the rapid disk rotation.

B. two opposite directions across the accretion disk and rotating with it

C. two opposite directions perpendicular to the accretion disk of the black hole

D. single direction above the accretion disk, the precession of which sweeps the jet along the surface of a cone

32. Measurement of structure in the cosmic microwave background radiation has recently indicated that we live in a flat universe between a closed and an open universe, and yet the measured density of detected matter and radiation is only 20-40% of the critical density required for a flat universe. In what form is the other 60-80% of the "matter" thought to be?

A. neutrinos, which have very little rest mass and are very difficult to detect, but are very abundant

B. myriads of small primordial black holes whose gravitational effects are spread throughout the universe and which emit no radiation

C. dark energy emitting no visible radiation

D. antimatter, which generates a negative gravitational effect and emits radiation only if it meets matter and is annihilated

33. What is believed to be the source of ultra-high-energy cosmic rays?

A. globular clusters

B. active supernovas

C. quasars

D. black holes

34. Approximately how far is the Sun from the center of the Milky Way Galaxy?

A. 160 kpc

B. 49 kpc

C. 2 kpc

D. 8 kpc

35. One object that is believed to be a black hole in the Milky Way Galaxy is the

A. Vela pulsar.

B. central star in the Crab Nebula.

C. central star in the planetary nebula, the Ring Nebula in Lyra.

D. powerful X-ray source Cygnus X-1.

36. The largest range of sizes of galaxies is found in which class of galaxies?

A. starburst galaxies

B. irregular galaxies

C. spiral galaxies

D. elliptical galaxies

37. We believe a supermassive black hole of three billion solar masses exists at the center of the giant elliptical galaxy M87. Which one of the following is not a piece of evidence used to deduce this?

A. This galaxy is a powerful source of X rays.

B. Multiple images of the galaxy have been formed by gravitational lensing.

C. The density of stars near the center of the galaxy is extraordinarily high.

D. The galaxy has a bright, starlike nucleus.

38. At what times during the Big Bang were all four fundamental forces unified?

A. until 10-24 s, after the start of the Big Bang, when the inflationary era ended

B. during the first 500,000 years from the start of the Big Bang, when the universe was dominated by radiation

C. until 10-6 s after the start of the Big Bang, when the era of quark confinement ended

D. during the Planck era, up to 10-43 s, after the start of the Big Bang

39. What is the observed distribution of the longer-living gamma-ray bursters in the sky?

A. uniform over the entire sky, indicating an origin at "cosmological" distances

B. clumpy but not coinciding with any known galaxy clusters, indicating an origin in a new kind of astronomical object

C. concentrated primarily along the plane of the Milky Way, indicating an origin in the Galaxy

D. clumpy, approximately coinciding with large clusters of galaxies such as the Coma cluster

40. A clock is moving across your line of sight with its face turned toward you. Which of the following statements about this clock, as seen by you, is not correct?

A. The clock will appear denser than it would if it were at rest.

B. The clock will run slow compared with a clock in your hand.

C. The clock will appear thinner, front to back, than it would if it were at rest.

D. The clock will appear shorter than it would if it were at rest.