Evolution of stars-Test I
Multiple Choice
Identify the letter of the choice that best completes the statement or answers the question.
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1. The hydrogen lines in spectral type A stars
a. are most narrow for supergiants.
b. are most narrow for main sequence stars.
c. can not be used to estimate the luminosity of the star.
d. are very weak and difficult to see.
e. are useful in determining the apparent magnitude of the star.
2. Parallax would be easier to measure if
a. Earth's orbit were larger.
b. the stars were farther away.
c. Earth moved faster along its orbit.
d. all of these
e. none of these
3. Absolute visual magnitude is
a. the apparent magnitude of a star observed from Earth.
b. the luminosity of a star observed from a distance of 1000 pc.
c. the apparent magnitude of a star observed from a distance of 10 pc.
d. the luminosity of a star observed from Earth.
e. c and d
4. A star's luminosity depends only on the star's
a. distance and diameter.
b. temperature and distance.
c. distance.
d. temperature and diameter.
e. apparent magnitude.
5. 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
6. In the H-R diagram, 90 percent of all stars are
a. in the giant region.
b. in the supergiant region.
c. among the B stars.
d. among the G stars.
e. on the main sequence.
7. 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.
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d. they are cooler but have about the same luminosity.
e. they have a larger absolute magnitude than the sun.
8. Giant stars are
I.
II.
III.
IV.
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9.
____
10.
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11.
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12.
a. I & II
b. II & IV
c. I, II, & IV
d. II, III, & IV
e. I, II, III, & IV
Compared with the spectral lines in the solar spectrum, lines in a supergiant spectrum are
a. more narrow.
b. broader.
c. weaker.
d. stronger.
e. b and c
The most common stars are
a. supergiants.
b. giants.
c. upper main sequence stars.
d. white dwarfs.
e. lower main sequence stars.
The __________ of a star is a measure of the total energy radiated by the star in one second.
a. absolute visual magnitude
b. apparent visual magnitude
c. luminosity class
d. spectral type
e. luminosity
Sheat is an M2 II star. Based on this information which of the following are true?
I.
II.
III.
IV.
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more luminous than the sun.
larger in diameter than the sun.
cooler than B stars.
located above the main sequence stars in the H-R diagram.
Sheat has a surface temperature less than the sun.
Sheat has a diameter that is greater than that of the sun.
Sheat is more luminous than the sun.
Sheat is located near the upper left hand corner in the HR diagram.
a. I & II
b. II & IV
c. II, III, & IV
d. I, II, & III
e. I, II, III, & IV
13.  Circini is an O 8.5 V star. Based on this information which of the following are true?
I.
II.
III.
IV.
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 Circini has a surface temperature less than the sun.
 Circini has a diameter that is greater than that of the sun.
 Circini is more luminous than the sun.
 Circini is located near the upper left hand corner in the HR diagram.
a. I & II
b. II & IV
c. II, III, & IV
d. I, II, & III
e. I, II, III, & IV
14. To determine the period of a visual binary, we must measure
a. brightness.
b. position.
c. wavelengths.
d. luminosity.
e. temperature.
15. In a binary system, the more massive star
a. is at the center of mass.
b. is farthest from the center of mass.
c. is nearest the center of mass.
d. follows the largest orbit.
e. shows a larger Doppler shift in its spectral lines.
16. Spectroscopic binaries are difficult to analyze because
a. we can't measure the radial velocities of each star in the system.
b. we can't see the shape of the orbit.
c. we can't find the diameters of the stars.
d. we can't determine the luminosities of the stars.
e. the Doppler shift is not measurable.
Figure 8-1
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17. Which star in Figure 8-1 above is most like the sun?
a. Alnilam
b. Antares
c. Arcturus
d. HR 5337
e. Sirius B
18. Which star in Figure 8-1 above has the greatest surface temperature?
a. Alnilam
b. Antares
c. Arcturus
d. HR 5337
e. Sirius B
19. Which of the stars in Figure 8-1 above has the largest absolute visual magnitude?
a. Alnilam
b. Antares
c. Arcturus
d. HR 5337
e. Sirius B
20. An eclipsing binary will
a. be more luminous than a visual binary.
b. always be a spectroscopic binary.
c. give off most of its light in the infrared.
d. show a constant Doppler shift in its spectral lines.
e. show two stars with variable proper motion.
21. If we can solve the orbital motion of an eclipsing binary, we can find
a. the masses of the stars.
b. the diameters of the stars.
c. the distance to the binary.
d. all of the above
e. both a and b
22. Which of the following best obey the mass-luminosity relation?
a. main sequence stars
b. giant stars
c. supergiant stars
d. white dwarfs
e. all of the above
23. Which of the following stars is most dense?
a. a supergiant star
b. a main sequence star
c. a giant star
d. a white dwarf
e. the sun
24. A spectroscopic binary shows periodic variations in its
a. radial velocity.
b. proper motion.
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25.
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26.
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27.
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28.
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c. brightness.
d. mass.
e. spectral type.
Stars on the main sequence with the greatest mass
a. are spectral type M stars.
b. are spectral type O stars.
c. are located at the bottom of the main sequence in the HR diagram.
d. have masses very similar to the sun.
e. both b and c
The star Algol is
a. an astrometric binary.
b. a single line spectroscopic binary.
c. a visual binary.
d. an eclipsing binary.
e. none of the above
The total mass of a binary system can be calculated from
a. the ratio of the angular separation from the center of mass of each of the stars.
b. the distance to the binary and its radial velocity.
c. the semi major axis and period of the orbit.
d. the radial velocities of the two stars.
e. the time required for the small star to eclipse the larger star.
The diagram below illustrates two stars in a visual binary system and the center of mass of this
system. Based on this diagram, what is the ratio of the mass of star A to the mass of star B?
a. 2 to 1
b. 1 to 2
c. 2 to 3
d. 3 to 2
e. 1 to 3
29. If a star has a parallax of 0.02 seconds of arc, then its distance is
a. 20 pc
b. 50 pc
c. 2 pc
d. 5 pc
e. 500 pc
30. If a star with an absolute magnitude of -5 has an apparent magnitude of +5, then its distance is
a. 1 pc.
b. 10 pc.
c. 100 pc.
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d. 1000 pc
e. 10,000 pc.
31. An eclipsing binary has been analyzed and it has been determined that the ratio of the mass of star
A to the mass of star B is 6 and the total mass of the two stars is 26 solar masses. What are the
masses of star A and star B.
a. Star A has a mass of 1 solar mass and star B has a mass of 6 solar masses.
b. Star A has a mass of 20 solar mass and star B has a mass of 6 solar masses.
c. Star A has a mass of 31.2 solar mass and star B has a mass of 5.2 solar masses.
d. Star A has a mass of 22.3 solar mass and star B has a mass of 3.7 solar masses.
e. The masses of star A and star B cannot be determined from the information given.
32. What is the total mass of a binary star system with P = 20 yr and a = 10 AU?
a. 2 solar masses
b. 2.5 solar masses
c. 0.5 solar mass
d. 80 solar masses
e. 0.4 solar mass
33. The diagram below shows the radial velocity curve of a double-line spectroscopic binary. Based on
this radial velocity curve, which of the following statements is correct?
a. Star A is twice the mass of star B.
b. Star B is twice the mass of star A.
c. Star A is ten times the mass of star B.
d. Star B is ten times the mass of star A.
e. Star A and Star B have the same mass.
34. In the light curve below, what is the period of the binary?
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a. 5 days
b. 32.5 days
c. 7.5 days
d. 42.5 days
e. 50 days
35. At what point in the light curve below is the cool star in front of the hotter star?
a.
b.
c.
d.
e.
1
2
3
4
5
Table 8-1
Star
65 Tau
HR 4621
 Pic
58 Ori
HR 2491
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mv
4.2
2.6
-1.5
Mv
-0.3
1.8
-6.0
d (pc)
Parallax
(sec of arc)
Spectral
Type
0.025
A7 IV
B2 IV
A7 V
M2 I
A1 V
20
0.005
2.5
36. Which star in Table 8-1 above would appear the faintest in the night sky?
a. 65 Tau
b. HR 4621
c.  Pic
d. 58 Ori
e. HR 2491
37. Which star in Table 8-1 above has the greatest luminosity?
a. 65 Tau
b. HR 4621
c.  Pic
d. 58 Ori
e. HR 2491
38. Which star in Table 8-1 above is the closest to Earth?
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a. 65 Tau
b. HR 4621
c.  Pic
d. 58 Ori
e. HR 2491
39. Which star in Table 8-1 above has the greatest surface temperature?
a. 65 Tau
b. HR 4621
c.  Pic
d. 58 Ori
e. HR 2491
40. Which star in Table 8-1 above has the greatest diameter?
a. 65 Tau
b. HR 4621
c.  Pic
d. 58 Ori
e. HR 2491
Table 8-2
Star
 Cen
HR 4607
HR 4758
HD 39801
9 CMa
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d (pc)
Parallax
(sec of arc)
Spectral
Type
0.026
0.039
B2 IV
G8 III
G0 V
M2 I
A1 V
20
0.005
2.5
41. Which star in Table 8-2 above is the closest to Earth?
a.  Cen
b. HR 4607
c. HR 4758
d. HD 39801
e. 9 CMa
42. Which star in Table 8-2 above has the greatest surface temperature?
a.  Cen
b. HR 4607
c. HR 4758
d. HD 39801
e. 9 CMa
43. Which star in Table 8-2 above has the greatest diameter?
a.  Cen
b. HR 4607
c. HR 4758
d. HD 39801
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44.
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45.
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46.
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47.
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48.
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49.
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50.
e. 9 CMa
If the orbital velocity of an eclipsing binary is 97 km/sec and the smaller star is completely
eclipsed in 2 hours, what is the diameter of the smaller star?
a. 175,000 km
b. 350,000 km
c. 194 km
d. 700,000 km
e. 4656 km
A 2 solar mass star on the main sequence would have a luminosity of approximately __________
solar luminosities.
a. 2
b. 4
c. 11
d. 0.5
e. 0.25
Protostars are difficult to observe because
a. the protostar stage is very short.
b. they are surrounded by cocoons of gas and dust.
c. they radiate mainly in the infrared.
d. all of the above
e. they are all so far away that the light hasn't reached us yet.
The nuclear reactions in a star's core remain under control so long as
a. luminosity depends on mass.
b. pressure depends on temperature.
c. density depends on mass.
d. weight depends on temperature.
e. temperature depends on mass.
Interstellar gas clouds may collapse to form stars if they
a. have very high temperatures.
b. encounter a shock wave.
c. rotate rapidly.
d. are located near main sequence spectral type K and M stars.
e. all of the above.
__________ are small luminous nebulae excited by nearby young stars.
a. T Tauri stars
b. Herbig-Haro objects
c. O associations
d. Bok Globule
e. Giant molecular clouds
Opacity is
a. the balance between the pressure and force of gravity inside a star.
b. the force that binds protons and neutrons together to form a nucleus.
c. the force that binds an electron to the nucleus in an atom.
d. a measure of the ease with which photons can pass through a gas.
e. the temperature and density at which a gas will undergo thermonuclear fusion.
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51. The Great Nebula in Orion
a. is a Herbig-Haro object.
b. is a reflection nebula.
c. is an emission nebula.
d. contains only young low mass stars.
e. is believed to be about 5 billion years old.
52. __________ is the thermonuclear fusion of hydrogen to form helium operating in the cores of
massive stars on the main sequence.
a. The CNO cycle
b. The proton-proton chain
c. Hydrostatic equilibrium
d. The neutrino process
e. none of the above
53. 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
54. 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.
55. The carbon-nitrogen-oxygen cycle
a. operates at a slightly lower temperature than the proton-proton chain.
b. is most efficient in star less massive than the sun.
c. occurs when carbon and oxygen combine to form nitrogen, which produces
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56.
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57.
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58.
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59.
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60.
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61.
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62.
energy.
d. produces the energy responsible for bipolar flows.
e. combines four hydrogen nuclei to form one helium nucleus, which produces
energy.
What causes the outward pressure that balances the inward pull of gravity in a star?
a. The outward flow of energy.
b. The opacity of the gas.
c. The temperature of the gas
d. The density of the gas
e. c and d
The free-fall contraction of a molecular cloud
a. can be initiated by shock waves from supernovae.
b. can be initiated by nearby spectral type G stars.
c. can be initiated by the rotation of the cloud.
d. causes the cloud to become transparent to ultraviolet radiation.
e. causes the particles in the cloud to decrease the speed with which they move.
Convection is important in stars because it
a. increases the temperature of the star.
b. mixes the gases of the star.
c. transports energy outward in the star.
d. carries the neutrinos to the surface of the star where they can escape.
e. b and c
__________ occurs when most of the material collapsing to form a protostar has fallen into a disk
around the star and a strong wind from the warm protostar ejects material from its poles.
a. An emission nebula
b. Hydrostatic equilibrium
c. The proton-proton chain
d. The thermonuclear fusion of hydrogen
e. A bipolar flow
Which of the following is not evidence of the existence of an interstellar medium?
a. extinction
b. narrow calcium lines in the spectra of O and B stars
c. reddening
d. dark clouds
e. molecular bands in the spectra of cool stars
Molecular clouds can be observed
a. using infrared telescopes to detect ionized gas in the clouds.
b. using x-ray telescope to observe the x-ray radiation from the molecules in the
cloud.
c. using radio telescopes to observe the CO emission from the clouds.
d. by looking for blue wispy regions near star clusters.
e. by looking for the 21-cm radiation from hydrogen.
The main sequence has a limit at the lower end because
a. low mass stars form from the interstellar medium very rarely.
b. low mass objects are composed primarily of solids, not gases.
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c. pressure does not depend on temperature in degenerate matter.
d. the lower limit represents when the radius of the star would be zero.
e. there is a minimum temperature for hydrogen fusion.
63. 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.
64. 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.
65. The lowest mass object that can initiate thermonuclear fusion of hydrogen has a mass of about
a. 1 M .
b. 60 M .
c. 0.5 M .
d. 0.08 M .
e. 0.001 M .
66. What is the lifetime of a 10 M star on the main sequence?
a. 3.2  107 years
b. 320 years
c. 3.2  1012 years
d. 1  109 years
e. 1  1011 years
67. __________ require(s) that a young hot star (T 25,000 K) be relatively nearby.
a. Emission nebulae
b. HI regions
c. Molecular clouds
d. The hot gas of the interstellar medium
e. 21 cm radiation
68. The extinction of starlight due to the interstellar medium
I.
II.
III.
IV.
a.
b.
c.
d.
is the greatest in the ultraviolet.
is the greatest in the infrared.
is caused by ionized hydrogen.
is caused by dust particles.
I & III
II & III
I & IV
II & IV
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69.
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70.
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71.
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72.
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73.
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74.
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75.
e. only IV
__________ are small dark nebulae about 1 light-year in diameter that contain 10 to 1,000 solar
masses.
a. HI regions
b. HII regions
c. Emission nebulae
d. Bok globules
e. Reflection nebulae
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.
Stars are born in
a. reflection nebulae.
b. dense molecular clouds.
c. HII regions.
d. the intercloud medium.
e. the local bubble.
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
As a star exhausts hydrogen in its core, it
a. becomes hotter and more luminous.
b. becomes cooler and more luminous.
c. becomes hotter and less luminous.
d. becomes cooler and less luminous.
e. it becomes larger in radius and hotter.
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.
In degenerate matter
a. pressure depends only on the temperature.
b. temperature depends only on density.
c. pressure does not depend on temperature.
d. pressure does not depend on density.
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e. b and c
76. Giant and supergiant stars are rare because
a. they do not form as often as main sequence stars.
b. the giant and supergiant stage is unstable.
c. the giant and supergiant stage is very short.
d. helium is very rare.
e. helium flash destroys many of the stars before they can become giants and
supergiants.
77. Star cluster are important to our study of stars because
a. all stars formed in star clusters.
b. the sun was once a member of a globular cluster.
c. they give us a method to test the our theories and models of stellar evolution.
d. they are the only objects that contain Cepheid variables.
e. all of the above
78. 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.
79. The triple alpha process
a. controls the pulsations in Cepheid variable stars.
b. is the nuclear fusion of hydrogen to helium in massive stars.
c. is the process that produces the neutrinos we receive from the sun.
d. requires a temperature of about 5,000,000 K to operate
e. occurs during helium flash.
80. The lowest mass object that can initiate thermonuclear fusion of hydrogen has a mass of about
a. 1 M .
b. 60 M .
c. 0.5 M .
d. 0.08 M .
e. 0.001 M .
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81. Which of the following nuclear fuels does a one solar mass star use over the course of its entire
evolution?
a. hydrogen
b. hydrogen and helium
c. hydrogen, helium, and carbon
d. hydrogen, helium, carbon, and neon
e. hydrogen, helium, carbon, neon, and oxygen.
82. Helium flash occurs
a. because helium is very explosive and cannot be controlled when the nuclear
reactions occur.
b. because degenerate electrons in the core do not allow the core to expand as it heats
up.
c. in Cepheid variables.
d. in stars with masses less than 0.4 M .
e. none of the above
83. Stars in a star cluster
a. all have the same age.
b. all have the same chemical composition.
c. all have the same luminosity.
d. all of the above
e. a and b above
84. 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  1010 years
b. 3.3  109 years
c. 6.4  108 years
d. 1.6  1011 years
e. The age of a star cluster can not be determined from the mass of stars at the turnoff
point.
85. In the diagram below, which point indicates the location on the HR diagram of a one solar mass
star when it undergoes helium flash?
a. 1
b. 2
c. 3
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86.
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87.
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88.
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89.
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90.
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91.
____
92.
d. 4
e. 5
The lowest-mass stars cannot become giants because
a. they do not contain helium.
b. they rotate too slowly.
c. they cannot heat their centers hot enough.
d. they contain strong magnetic fields.
e. they never use up their hydrogen.
A planetary nebula is
a. the expelled outer envelope of a medium mass star.
b. produced by a supernova explosion.
c. produced by a nova explosion.
d. a nebula within which planets are forming.
e. a cloud of hot gas surrounding a planet.
The Chandrasekhar limit tells us that
a. accretion disks can grow hot through friction.
b. neutron stars of more than 3 solar masses are not stable.
c. white dwarfs must contain more than 1.4 solar masses.
d. not all stars will end up as white dwarfs.
e. stars with a mass less than 0.5 solar masses will not go through helium flash.
A Type I supernova is believed to occur when
a. the core of a massive star collapses.
b. carbon detonation occurs.
c. a white dwarf exceeds the Chandrasekhar limit.
d. the cores of massive stars collapse.
e. neutrinos in a massive star become degenerate and form a shock wave that
explodes the star.
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.
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. the brightening of supernovae a few days after they are first visible
d. underground counts from solar neutrinos.
e. the detection of neutrinos from the supernova of 1987.
Synchrotron radiation is produced by
a. objects with temperature below 10,000 K.
b. high-velocity electrons moving through a magnetic field.
c. cold hydrogen atoms in space.
d. the collapsing cores of massive stars.
e. helium flash.
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93. A nova is almost always associated with
a. a very massive star.
b. a very young star.
c. a star undergoing helium flash.
d. a white dwarf in a close binary system.
e. a solar like star that has exhausted its hydrogen and helium.
94. The Algol paradox is explained by considering
a. the degenerate nature of the hydrogen on the surface of the white dwarf.
b. synchrotron radiation
c. the rate of expansion of the shock wave inside the supernova.
d. the rotation rate of a neutron star.
e. mass transfer between the two stars in a binary system.
95. Stars with masses between 0.4 M and 4 M
a. undergo thermonuclear fusion of hydrogen and helium, but never get hot enough to
ignite carbon.
b. undergo thermonuclear fusion of hydrogen, but never get hot enough to ignite
helium.
c. produce type-I supernovae after they exhaust their nuclear fuels.
d. produce type-II supernovae after they exhaust their nuclear fuels.
e. undergo carbon detonation.
96. A type-II supernova
a. occurs when a white dwarf's mass exceeds the Chandrasekhar limit.
b. is the result of helium flash.
c. is characterized by a spectrum that shows hydrogen lines.
d. occurs when the iron core of a massive star collapses.
e. c and d
97. Synchrotron radiation is produced
a. in planetary nebulae.
b. by red dwarfs.
c. massive stars as their iron core collapses.
d. in supernova remnants.
e. neutrinos
98. 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
99. A white dwarf is composed of
a. hydrogen nuclei and degenerate electrons.
b. helium nuclei and normal electrons.
c. carbon and oxygen nuclei and degenerate electrons.
d. degenerate iron nuclei.
e. a helium burning core and a hydrogen burning shell.
____ 100. A planetary nebula
a. produces an absorption spectrum.
b. produces an emission spectrum.
c. is contracting to form planets.
d. is contracting to form a star.
e. is the result of carbon detonation in a 1 M star.
____ 101. If the theory that novae occur in close binary systems is correct, then novae should
a. produce synchrotron radiation.
b. occur in regions of star formation.
c. not occur in old star clusters.
d. all be visual binaries.
e. repeat after some interval.
____ 102. As a white dwarf cools its radius will not change because
a. pressure due to nuclear reactions in a shell just below the surface keeps it from
collapsing.
b. pressure does not depend on temperature for a white dwarf because the electrons
are degenerate.
c. pressure does not depend on temperature because the white dwarf is too hot.
d. pressure does not depend on temperature because the star has exhausted all its
nuclear fuels.
e. material accreting onto it from a companion maintains a constant radius.
____ 103. 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.
b.
c.
d.
e.
less than 50
50
150
250
more than 250
Completion
Complete each sentence or statement.
104. 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 __________.
105. A G2 I star is __________ in diameter and __________ luminous than the sun.
106. __________ can be used to determine the distance to a star when the spectrum of the star can be
used to determine its spectral type and luminosity class.
107. Luminosity class IV objects are known as __________.
108. On the HR diagram below, indicate the location of the white dwarf stars.
109. For stars on the main sequence, the luminosity can be estimated by the formula L = __________.
110. The masses and diameters of each star in the binary can be determined from __________ binaries.
111. Below is a radial velocity curve for a spectroscopic binary. Which of the stars is most massive?
__________
112. If we divide the mass of a star by its volume we calculate the star's __________.
113. __________ is the resistance of a gas to the flow of radiation.
114. The condition of __________ means that the force due to gravity pushing down on a layer is
exactly equal to the pressure pushing outward on that layer.
115. Stars with masses greater than 1.1 solar masses use the __________ to convert hydrogen into
helium and produce energy
116. Energy transport by __________ is important when photons cannot readily travel through a gas.
117. __________ appear reddish in color due to the light emitted by the Balmer series of the hydrogen
atom.
118. The pressure of an interstellar gas cloud depends on the clouds __________ and __________.
119. A gas in which the pressure no longer depends on the temperature of the gas is said to be
__________.
120. The age of a star cluster can be determined from the __________ of the cluster.
121. The maximum mass of a white dwarf is __________ solar masses.
122. A(n) __________ is the expulsion of the outer layers of a moderate mass star that has a degenerate
carbon and oxygen core.
123. Electrons moving in a strong magnetic field emit __________ radiation.
124. Mass can flow from one star in a binary system to its companion through the first __________
point.
True/False
Indicate whether the sentence or statement is true or false.
____ 125. A star whose parallax is 0.01 seconds arc is at a distance of 1000 pc.
____ 126. The absolute magnitude of a star is the apparent magnitude it would have if it were 10 pc from
Earth.
____ 127. The location of a star in the HR diagram indicates its temperature and intrinsic brightness.
____ 128. Absorption lines in the spectra of supergiant stars are broader than the same spectral lines in main
sequence stars of the same spectral type.
____ 129. Giant stars are members of luminosity class III.
____ 130. If a star is twice as hot as the sun and only half the sun's diameter, it will be less luminous than the
sun.
____ 131. The method of spectroscopic parallax cannot be applied to stars beyond about 100 pc.
____ 132. The most common kinds of stars are low-luminosity stars.
____ 133. Supergiants are about as common as the sun.
____ 134. White dwarfs have such a low luminosity that even the nearest white dwarfs are not visible to the
naked eye.
____ 135. To observe a visual binary, we must measure radial velocities.
____ 136. The more massive star in a binary system is always farthest from the center of mass.
____ 137. If a binary system has a period of 4 years and a separation of 5 AU, then the total mass is 7.8 solar
masses.
____ 138. To observe a spectroscopic binary, we must be able to see both stars individually.
____ 139. We can find the masses and diameters of stars that are in eclipsing binary systems.
____ 140. When we see a binary system producing eclipses, we know that the orbit is nearly edge-on.
____ 141. The most massive main-sequence stars are the M stars.
____ 142. The densest stars in the H-R diagram are the white dwarfs.
____ 143. Some young star clusters contain large numbers of T Tauri stars.
____ 144. Ninety percent of all stars fuse helium to form carbon and lie on the main sequence.
____ 145. Nuclear fusion in stars is controlled by the dependence of density on mass.
____ 146. The sun has a core in which energy travels outward primarily by radiation.
____ 147. The sun makes most of its energy by the CNO cycle.
____ 148. Energy flows by radiation or convection inside stars but almost never by conduction.
____ 149. Hydrostatic equilibrium refers to the balance between weight and pressure.
____ 150. The Orion region contains young main sequence stars and an emission nebula, but the original
molecular cloud they formed out of has been dispersed.
____ 151. T Tauri stars are believed to be young, high mass main sequence stars.
____ 152. The dust in the interstellar medium can make distant stars look redder than they really are.
____ 153. Bok globules are small, dark fragments of the interstellar medium.
____ 154. The thermal motions of the atoms in a gas cloud can make it collapse to form a protostar.
____ 155. Molecular clouds are mapped using CO instead of hydrogen because CO is much more abundant
than hydrogen in molecular clouds.
____ 156. HII regions are found near stars cooler than 25,000 K because large amounts of ultraviolet photons
would destroy the hydrogen atoms in the gas.
____ 157. The pressure of a gas depends on the temperature and density of the gas.
____ 158. Stars swell into giants when hydrogen is exhausted in their centers.
____ 159. The helium flash is the cause of some supernovae.
____ 160. Helium fusion does not begin until the star has entered the giant region of the H-R diagram.
____ 161. Even in degenerate matter, pressure depends on temperature.
____ 162. Giant and supergiant stars are rare because that stage of stellar evolution is short.
____ 163. Young star clusters have bluer turn-off points than old clusters.
____ 164. Planetary nebulae are sites of planet formation.
____ 165. Stars less massive than 0.4 solar mass never become giant stars.
____ 166. Once a star ejects a planetary nebula, it becomes a white dwarf.
____ 167. No known white dwarf has a mass greater than the Chandrasekhar limit.
____ 168. Because more massive stars have more gravitational energy, they can fuse heavier nuclear fuels.
____ 169. The sun will eventually become a supernova.
____ 170. Type II supernovae are believed to occur when the cores of massive stars collapse.
____ 171. Synchrotron radiation occurs when high speed electrons move through a magnetic field.
____ 172. A Type II supernova produces a planetary nebula.
____ 173. A nova destroys the star and leaves behind a white dwarf.
Evolution of stars-Test I
Answer Section
MULTIPLE CHOICE
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
34.
35.
36.
37.
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
A
A
C
D
D
E
A
E
A
E
E
D
C
B
C
B
D
A
E
B
E
A
D
A
B
D
C
B
B
D
D
B
B
B
D
A
D
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OBJ: TYPE: Web Quiz
OBJ: TYPE: Web Quiz
OBJ: TYPE: Web Quiz
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38.
39.
40.
41.
42.
43.
44.
45.
46.
47.
48.
49.
50.
51.
52.
53.
54.
55.
56.
57.
58.
59.
60.
61.
62.
63.
64.
65.
66.
67.
68.
69.
70.
71.
72.
73.
74.
75.
76.
77.
78.
79.
80.
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
E
B
D
E
A
D
D
C
D
B
B
B
D
C
A
D
E
E
A
A
E
E
E
C
E
C
C
D
A
A
C
D
D
B
B
B
E
C
C
C
C
E
D
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OBJ: TYPE: Web Quiz
OBJ: TYPE: Web Quiz
OBJ: TYPE: Web Quiz
OBJ: TYPE: Web Quiz
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OBJ: TYPE: Web Quiz
OBJ: TYPE: Web Quiz
OBJ: TYPE: Web Quiz
81.
82.
83.
84.
85.
86.
87.
88.
89.
90.
91.
92.
93.
94.
95.
96.
97.
98.
99.
100.
101.
102.
103.
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
B
B
E
C
E
C
A
D
C
D
E
B
D
E
A
E
D
C
C
B
E
B
C
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COMPLETION
104.
105.
106.
107.
108.
109.
110.
111.
112.
113.
114.
115.
116.
117.
118.
119.
ANS: +5.18
ANS: larger; more
ANS: Spectroscopic parallax
ANS: subgiants
ANS: 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 Figure 8-8 in the text).
ANS: M3.5
ANS: eclipsing
ANS: Star B
ANS: average density
ANS: Opacity
ANS: hydrostatic equilibrium
ANS: CNO cycle
ANS: convection
ANS: Emission nebulae or HII regions
ANS: temperature; density
ANS: degenerate
120.
121.
122.
123.
124.
ANS:
ANS:
ANS:
ANS:
ANS:
turnoff point
1.4
planetary nebula
synchrotron
Lagrangian
TRUE/FALSE
125.
126.
127.
128.
129.
130.
131.
132.
133.
134.
135.
136.
137.
138.
139.
140.
141.
142.
143.
144.
145.
146.
147.
148.
149.
150.
151.
152.
153.
154.
155.
156.
157.
158.
159.
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
F
T
T
F
T
F
F
T
F
T
F
F
T
F
T
T
F
T
T
F
F
T
F
T
T
F
F
T
T
F
F
F
T
T
F
160.
161.
162.
163.
164.
165.
166.
167.
168.
169.
170.
171.
172.
173.
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
T
F
T
T
F
T
T
T
T
F
T
T
F
F