Stars2 True/False



Download 366.85 Kb.
Date26.05.2018
Size366.85 Kb.
#48643
Stars2

True/False

Indicate whether the sentence or statement is true or false.

____ 1. Stars support their weight by generating energy in their centers.

____ 2. Young star clusters have bluer turn-off points than old clusters.

____ 3. Stars less massive than 0.4 solar mass never become giant stars.

____ 4. No known white dwarf has a mass greater than the Chandrasekhar limit.

____ 5. Because more massive stars have more gravitational energy, they can fuse heavier nuclear fuels.

____ 6. A Type II supernova produces a planetary nebula.

____ 7. A nova destroys the star and leaves behind a white dwarf.

____ 8. We expect neutron stars to spin rapidly because they conserve angular momentum.

____ 9. The event horizon marks the boundary within which the density is roughly the same as that of the atomic nucleus.

____ 10. To tell the difference between a neutron star and a black hole in an X ray binary, we must find the temperature of the object.

Multiple Choice

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

____ 11. A star's absolute magnitude depends only on the star's



a.

distance and diameter.

b.

temperature and distance.

c.

distance.

d.

temperature and diameter.

e.

apparent magnitude.

____ 12. In an H-R Diagram, stars with the smallest radius are found in the _______ of the diagram.



a.

center

b.

upper left corner

c.

upper right corner

d.

lower left corner

e.

lower right corner

____ 13. We know that giant stars are larger in diameter than the sun because



a.

they are more luminous but have about the same temperature.

b.

they are less luminous but have about the same temperature.

c.

they are hotter but have about the same luminosity.

d.

they are cooler but have about the same luminosity.

e.

they have a larger absolute magnitude than the sun.

____ 14. The most common stars are



a.

supergiants.

b.

giants.

c.

upper main sequence stars.

d.

white dwarfs.

e.

lower main sequence stars.

____ 15. The star Sadir has an absolute bolometric magnitude of -5.3 and the absolute bolometric magnitude of the sun is +4.7. Based on this information, which of the following statements is true.



a.

Sadir has a greater surface temperature than the sun.

b.

Sadir has a larger diameter than the sun.

c.

Sadir is 10,000 times more luminous than the sun.

d.

Sadir is 100 parsecs from Earth.

e.

all of the above

____ 16. The term "metastable levels" refers to



a.

regions within a molecular cloud that are not moving relative to the rest of the cloud.

b.

the upper energy level of the 21-cm transition in the hydrogen atom.

c.

the lower energy level of the 21-cm transition in the hydrogen atom.

d.

the boundary layers between HI regions and the hotter intercloud medium.

e.

energy levels in an atom that require a much longer time than average to decay and emit a photon.

____ 17. Coronal gas



a.

causes stars to look bluer than they normally would.

b.

causes the stars to twinkle.

c.

emits 21 cm radiation.

d.

is located near stars with surface temperatures greater than 25,000 K.

e.

has a temperature of about 1 million K.

____ 18. Due to the dust in the interstellar medium, a star will appear to an observer on Earth to be



a.

brighter and cooler than it really is.

b.

brighter and hotter than it really is.

c.

fainter and cooler than it really is.

d.

fainter and hotter than it really is.

e.

unchanged in brightness or apparent color.

____ 19. Absorption lines due to the interstellar medium indicate that some components of the interstellar medium are cold and of a very low density because



a.

the lines are blue shifted.

b.

the lines are red shifted.

c.

the lines are extremely broad.

d.

the lines are extremely narrow.

e.

the lines are much darker than the stellar lines.

____ 20. Absorption lines due to interstellar gas



a.

are wider than the lines from stars because the gas is hotter than most stars.

b.

are more narrow than the lines from stars because the gas has a lower pressure than stars.

c.

indicate that the interstellar medium contains dust.

d.

indicate that the interstellar medium is expanding away from the sun.

e.

none of the above

____ 21. Extinction by the interstellar medium dims starlight by about 2 magnitudes for every 1000 pc the light travels. What fraction of the photons remain from a star that is 5000 pc from an observer?



a.

1/10

b.

1/5

c.

1/25

d.

1/10,000

e.

1/100

____ 22. Which of the following have been suggested as explanations of the missing solar neutrinos?




I.

The sun is fusing helium but not hydrogen.

II.

Nuclear reactions do not produce neutrinos as fast as theory predicts.

III.

The sun may contain WIMPs.

IV.

Neutrinos may oscillate between three different flavors.




a.

only I

b.

only II

c.

III & IV

d.

II, III, & IV

e.

I, II, & IV

____ 23. _____________ are small luminous nebulae excited by nearby young stars.



a.

T Tauri stars

b.

Herbig-Haro objects

c.

O associations

d.

WIMPS

e.

Giant molecular clouds

____ 24. The region of the sun just below the photosphere



a.

is undergoing thermonuclear fusion using the proton-proton chain.

b.

is undergoing thermonuclear fusion using the CNO cycle.

c.

is transporting energy to the photosphere by convection.

d.

is not in hydrostatic equilibrium.

e.

a and c above

____ 25. The diagram below is an HR diagram. The line indicates the location of the main sequence. Which of the five labeled locations on the HR diagram indicates a luminosity and temperature similar to that of a T Tauri star.





a.

1

b.

2

c.

3

d.

4

e.

5

____ 26. If the sun produces energy by the proton-proton chain, then the center of the sun must have a temperature of at least



a.

104 K

b.

107 K

c.

1010 K

d.

1013 K

e.

1016 K

____ 27. In the proton-proton chain



a.

no neutrinos are produced.

b.

energy is released because a helium nucleus has a greater mass than a hydrogen nucleus.

c.

no photons are produced.

d.

carbon serves as a catalyst for the nuclear reaction.

e.

energy is produced in the form of gamma rays and the velocity of the created nuclei.

____ 28. Protons and neutrons are held together in the nucleus by



a.

the weak force.

b.

the gravitational force.

c.

the electrostatic force.

d.

the strong force.

e.

the opacity.

____ 29. There is a mass-luminosity relation because



a.

hydrogen fusion produces helium.

b.

stars expand when they become giants.

c.

stars support their weight by making energy.

d.

the helium flash occurs in degenerate matter.

e.

all stars on the main sequence have about the same radius.

____ 30. A star will experience a helium flash if



a.

it is more massive than about 6 solar masses.

b.

its core contains oxygen and helium.

c.

its mass on the main sequence was less than 0.1 solar masses.

d.

it is a supergiant.

e.

its core is degenerate when helium ignites.

____ 31. What is the approximate age of the star cluster in the diagram below?





a.

2 million years

b.

2 billion years

c.

10 billion years

d.

100 billion years

e.

The age of the cluster can not be estimated from an HR diagram of the cluster.

____ 32. If the stars at the turnoff point of a cluster have a mass of 3 M, what is the age of the cluster?



a.

3.0 x 1010 years

b.

3.3 x 109 years

c.

6.4 x 108 years

d.

1.6 x 1011 years

e.

The age of a star cluster can not be determined from the mass of stars at the turnoff point.

____ 33. Massive stars cannot generate energy through iron fusion because



a.

iron fusion requires very high density.

b.

stars contain very little iron.

c.

no star can get hot enough for iron fusion.

d.

iron is the most tightly bound of all nuclei.

e.

massive stars supernova before they create an iron core.

____ 34. The theory that the collapse of a massive star's iron core produces neutrinos was supported by



a.

the size and structure of the Crab nebula.

b.

laboratory measurements of the mass of the neutrino.

c.

calculation of models of core collapse.

d.

underground counts from solar neutrinos.

e.

the detection of neutrinos from the supernova of 1987.

____ 35. The Helix and Egg nebulae are



a.

supernova remnants.

b.

planetary nebulae.

c.

the result of carbon detonation.

d.

the result of the collapse of the iron core of each star.

e.

nebulae associated with Herbig-Haro objects.

____ 36. When material expanding away from a star in a binary system reaches the Roche surface



a.

the material will start to fall back toward the star.

b.

all of the material will accrete on to the companion.

c.

the material is no longer gravitationally bound to the star.

d.

the material will increase in temperature an eventually undergo thermonuclear fusion.

e.

c and d

____ 37. The diagram below shows a light curve from a supernova. How many days after maximum light did it take for the supernova to decrease in brightness by a factor of 100?





a.

25

b.

50

c.

100

d.

150

e.

250

____ 38. A supernova remnant is expanding in radius at the rate of 0.5 seconds of arc per year. Doppler shifts show that the velocity of expansion is 5700 km/sec. How far away is the supernova remnant?



a.

1140 pc

b.

11,400 km

c.

5700 pc

d.

24 pc

e.

2400 pc

____ 39. The peculiar system SS 433




I.

is emitting beams of energy and matter.

II.

is producing a spectrum with both a red and a blue shift

III.

probably contains an accretion disk.

IV.

is the result of a planetary nebula.




a.

I

b.

III

c.

II & III

d.

I, II, & III

e.

I, II, III, & IV

____ 40. Millisecond pulsars that are very old are



a.

believed to be the result of mass transfer from a companion that increases the mass of the pulsar.

b.

all single objects.

c.

not spinning as rapidly they seem because they have four hot spots that produce the flashes.

d.

x-ray binaries.

e.

gamma-ray bursters.


Completion

Complete each sentence or statement.

41. The parallax of the star 75 Leo is 0.10 and its apparent visual magnitude is +5.18. The absolute visual magnitude of 75 Leo is ____________.

42. Luminosity class IV objects are known as __________________.

43. On the HR diagram below, indicate the location of the white dwarf stars.


44. Molecules emit radiation at _____________ wavelengths.

45. __________ appear reddish in color due to the light emitted by the Balmer series of the hydrogen atom.

46. The ______________ is the thermonuclear fusion of helium to form carbon.

47. A gas in which the pressure no longer depends on the temperature of the gas is said to be _____________.

48. A(n) __________ is the sudden expulsion of the outer layers of a moderate mass star that has a dormant carbon core.

49. Electrons moving in a strong magnetic field emit _________________ radiation.

50. Material within the ____________ of a rotating black hole is forced to orbit the black hole due to the curvature of space-time, but could still escape the gravitational pull of the black hole.



Essay

51. If the sun and stars are supported by gas pressure, what supports a neutron star?

52. Why does our theory predict that neutron stars will have strong magnetic fields?
Stars2

Answer Section

TRUE/FALSE

1. T


2. T

3. T


4. T

5. T


6. F

7. F


8. T

9. F


10. F

MULTIPLE CHOICE

11. D


12. D

13. A


14. E

15. C


16. E

17. E


18. C

19. D


20. B

21. D


22. D

23. B


24. C

25. D


26. B

27. E


28. D

29. C


30. E

31. C


32. C

33. D


34. E

35. B


36. C

37. D


38. E

39. D


40. A

COMPLETION

41. +5.18

42. subgiants

43. An elongated region should be indicated that stretches from a luminosity of about 10-2 and spectral type B to luminosity of about 10-4 and spectral type G. (See Figures 9-8 and 9-9 in the text).

44. radio

45. Emission nebulae or HII regions

46. triple alpha process

47. degenerate

48. planetary nebula

49. synchrotron

50. ergosphere

ESSAY

51. Answer not provided.



52. Answer not provided.

Download 366.85 Kb.

Share with your friends:




The database is protected by copyright ©sckool.org 2023
send message

    Main page