Question 1

The fluctuation time for the brightnesses of quasars can be as short as a

Accepted Answer

A)  few seconds. 
B)  month. 
C)  day. 
D)  year. 
A)  few seconds. 
B)  month. 
C)  day. 
D)  year.

Question 2

For gravitational lensing of a distant quasar to occur, the galaxy producing the lensing must

Accepted Answer

A)  be rotating rapidly to produce the requisite curvature of space to bend the light beam. 
B)  be almost perfectly placed on a line between Earth and the quasar. 
C)  contain a supermassive black hole at its center. 
D)  be a dwarf galaxy; otherwise the quasar's light cannot pass through it and reach Earth. 
A)  be rotating rapidly to produce the requisite curvature of space to bend the light beam. 
B)  be almost perfectly placed on a line between Earth and the quasar. 
C)  contain a supermassive black hole at its center. 
D)  be a dwarf galaxy; otherwise the quasar's light cannot pass through it and reach Earth.

Question 3

The observed characteristics of a quasar are a

Accepted Answer

A)  diffuse circular image, no redshift of the spectrum, and often a very bright radio source. 
B)  starlike image, with a highly variable Doppler spectrum that shifts from red to blue, and often a very bright radio source. 
C)  starlike image, a highly redshifted spectrum, and sometimes an intense radio emitter. 
D)  starlike image, an extremely blueshifted spectrum, and often an intense radio emitter. 
A)  diffuse circular image, no redshift of the spectrum, and often a very bright radio source. 
B)  starlike image, with a highly variable Doppler spectrum that shifts from red to blue, and often a very bright radio source. 
C)  starlike image, a highly redshifted spectrum, and sometimes an intense radio emitter. 
D)  starlike image, an extremely blueshifted spectrum, and often an intense radio emitter.

Question 4

The energy output per second of a typical quasar is equal to that emitted by the Sun in 200 years. How much energy is this? The Sun's luminosity is 3.8 * 1026 watts.

Accepted Answer

A)  6.8 * 1028 Joules 
B)  1.2 * 1034 Joules 
C)  2.4 *1036 Joules 
D)  5.5 *1039 Joules 
A)  6.8 * 1028 Joules 
B)  1.2 * 1034 Joules 
C)  2.4 *1036 Joules 
D)  5.5 *1039 Joules

Question 5

Quasars appear to be

Accepted Answer

A)  very distant and intrinsically bright objects moving in random directions at high speeds. 
B)  very distant, intrinsically faint objects with very high blueshifts in their spectra. 
C)  relatively close with very high redshifts. 
D)  very distant, intrinsically bright objects with very high redshifts. 
A)  very distant and intrinsically bright objects moving in random directions at high speeds. 
B)  very distant, intrinsically faint objects with very high blueshifts in their spectra. 
C)  relatively close with very high redshifts. 
D)  very distant, intrinsically bright objects with very high redshifts.

Question 6

A BL Lacertae object is a(n)

Accepted Answer

A)  emission nebula containing a young T Tauri star. 
B)  rapidly spinning neutron star. 
C)  eclipsing binary star with a black hole as one component. 
D)  active galactic nucleus. 
A)  emission nebula containing a young T Tauri star. 
B)  rapidly spinning neutron star. 
C)  eclipsing binary star with a black hole as one component. 
D)  active galactic nucleus.

Question 7

Jets of gas coming from an AGN are associated with

Accepted Answer

A)  any supermassive black hole. 
B)  Schwarzschild black hole only. 
C)  slowly rotating Kerr black holes only. 
D)  rapidly rotating black holes only. 
A)  any supermassive black hole. 
B)  Schwarzschild black hole only. 
C)  slowly rotating Kerr black holes only. 
D)  rapidly rotating black holes only.

Question 8

Evidence obtained over the last few years indicates that a quasar is MOST likely

Accepted Answer

A)  the remnant core of an exploding star or supernova. 
B)  the focused image of a distant galaxy by the gravitational lens effect of a closer galaxy. 
C)  evidence of very intense star-building activity in certain distant dust and gas clouds. 
D)  powered by material near the central supermassive black hole of a very distant, very active galaxy. 
A)  the remnant core of an exploding star or supernova. 
B)  the focused image of a distant galaxy by the gravitational lens effect of a closer galaxy. 
C)  evidence of very intense star-building activity in certain distant dust and gas clouds. 
D)  powered by material near the central supermassive black hole of a very distant, very active galaxy.

Question 9

The intensity of radiation coming from an active galaxy

Accepted Answer

A)  remains remarkably constant during its long life. 
B)  decreases slightly at a constant rate as energy is radiated away. 
C)  ebbs and flows as the mass of the accretion disk around the black hole ebbs and flows. 
D)  ebbs and flows as the mass of the black hole ebbs and flows. 
A)  remains remarkably constant during its long life. 
B)  decreases slightly at a constant rate as energy is radiated away. 
C)  ebbs and flows as the mass of the accretion disk around the black hole ebbs and flows. 
D)  ebbs and flows as the mass of the black hole ebbs and flows.

Question 10

Most quasi-stellar objects (QSOs) produce their strongest emissions in which region of the electromagnetic spectrum?

Accepted Answer

A)  X- ray 
B)  visible 
C)  infrared 
D)  radio 
A)  X- ray 
B)  visible 
C)  infrared 
D)  radio

Question 11

Which of these objects is NOT classified as an active galaxy?

Accepted Answer

A)  Seyfert galaxy 
B)  BL Lacertae object 
C)  quasar 
D)  barred spiral 
A)  Seyfert galaxy 
B)  BL Lacertae object 
C)  quasar 
D)  barred spiral

Question 12

An astronomer is observing the radiation from a distant active galaxy and notices that the amplitude of the signal varies in strength regularly over a certain period. The maximum possible size for the source of this radiation can now be calculated from the

Accepted Answer

A)  period and the amplitude of the signal. 
B)  period but not the amplitude of the signal. 
C)  amplitude but not the period of the signal. 
D)  frequency of the radiation composing the signal. 
A)  period and the amplitude of the signal. 
B)  period but not the amplitude of the signal. 
C)  amplitude but not the period of the signal. 
D)  frequency of the radiation composing the signal.

Question 13

Which observations of the radiation from quasars indicate that quasars are physically very small objects compared with galaxies?

Accepted Answer

A)  their emission, which is mostly in the infrared and radio range 
B)  their starlike appearance on photographs, showing no structure 
C)  rapid fluctuations in output, often in less than 1 day 
D)  very high redshift of their light 
A)  their emission, which is mostly in the infrared and radio range 
B)  their starlike appearance on photographs, showing no structure 
C)  rapid fluctuations in output, often in less than 1 day 
D)  very high redshift of their light

Question 14

What is the relationship between the size of an object and the rate at which its radiant output can vary?

Accepted Answer

A)  Small objects can vary more rapidly. 
B)  Large objects can vary more rapidly. 
C)  The relationship depends on the wavelength of the radiant output. Large objects can vary more rapidly at long wavelengths, and smaller objects can vary more rapidly at shorter wavelengths. 
D)  There is no relationship between size and variation rate. 
A)  Small objects can vary more rapidly. 
B)  Large objects can vary more rapidly. 
C)  The relationship depends on the wavelength of the radiant output. Large objects can vary more rapidly at long wavelengths, and smaller objects can vary more rapidly at shorter wavelengths. 
D)  There is no relationship between size and variation rate.

Question 15

The closest quasar is Cygnus A, 635 million light-years away. What does the Hubble law give for its redshift?

Accepted Answer

A)  0.0326 
B)  0.046 
C)  0.091 
D)  0.15 
A)  0.0326 
B)  0.046 
C)  0.091 
D)  0.15

Question 16

Many bright radio sources at very large distances from the Sun appear to emit energy from two relatively widely spaced sources. What mechanism is thought to produce these double-radio emission regions?

Accepted Answer

A)  Two oppositely directed beams of light and radio energy illuminate the intergalactic dust and gas. 
B)  Two oppositely directed plasma jets from a central source produce radio energy as the plasma slows down. 
C)  These sources are two galaxies orbiting each other like binary stars. 
D)  The sources are in fact a single source and its reflection in a dense intergalactic gas and dust "mirror," or plasma sheet. 
A)  Two oppositely directed beams of light and radio energy illuminate the intergalactic dust and gas. 
B)  Two oppositely directed plasma jets from a central source produce radio energy as the plasma slows down. 
C)  These sources are two galaxies orbiting each other like binary stars. 
D)  The sources are in fact a single source and its reflection in a dense intergalactic gas and dust "mirror," or plasma sheet.

Question 17

What recent evidence seems to indicate that several nearby galaxies may contain supermassive black holes at their centers?

Accepted Answer

A)  The rotation curve of these galaxies shows no decrease in orbital velocity of stars as the radius of orbit increases out to the observable limit of the galaxy, indicating an unusual source of gravity. 
B)  Spectroscopic observations of stars near the centers of these galaxies show extremely fast orbital velocities, indicating the presence of a large mass to keep stars in orbit. 
C)  Extreme redshift of light from stars near the centers of these galaxies is caused by gravitational redshift from a very massive object. 
D)  These galaxies are rushing rapidly toward each other (and in at least one case, toward the Milky Way!) because of the gravitational attraction among them. 
A)  The rotation curve of these galaxies shows no decrease in orbital velocity of stars as the radius of orbit increases out to the observable limit of the galaxy, indicating an unusual source of gravity. 
B)  Spectroscopic observations of stars near the centers of these galaxies show extremely fast orbital velocities, indicating the presence of a large mass to keep stars in orbit. 
C)  Extreme redshift of light from stars near the centers of these galaxies is caused by gravitational redshift from a very massive object. 
D)  These galaxies are rushing rapidly toward each other (and in at least one case, toward the Milky Way!) because of the gravitational attraction among them.

Question 18

An electron moving in a magnetic field in space is forced to move in a spiral pattern. As it does so, it emits

Accepted Answer

A)  characteristic X-rays as the electron is slowed down by this motion. 
B)  visible light, mostly blue in color because the electron is forced to move in a circular path. 
C)  synchrotron radiation, mostly radio waves, since the electrons are accelerating. 
D)  nothing since such electrons are moving with a constant speed and are not therefore accelerating. 
A)  characteristic X-rays as the electron is slowed down by this motion. 
B)  visible light, mostly blue in color because the electron is forced to move in a circular path. 
C)  synchrotron radiation, mostly radio waves, since the electrons are accelerating. 
D)  nothing since such electrons are moving with a constant speed and are not therefore accelerating.

Question 19

All quasars appear to be

Accepted Answer

A)  moving toward Earth at very high speeds. 
B)  moving away from Earth at very high speeds. 
C)  very distant, intrinsically faint objects. 
D)  relatively close, very bright objects. 
A)  moving toward Earth at very high speeds. 
B)  moving away from Earth at very high speeds. 
C)  very distant, intrinsically faint objects. 
D)  relatively close, very bright objects.

Question 20

What observations convince astronomers that the energy source of a quasar is physically very small?

Accepted Answer

A)  rapid fluctuations in brightness since variations over 1 day mean that the source must be less than 1 light-day across 
B)  instant disappearance of the quasar when occulted by the Moon's edge as the Moon moves in front of a quasar, indicating a very small source size 
C)  sharpness of the emission lines in their optical spectra since motions within a large source would smear out the line shapes 
D)  extremely small size of the image of a quasar, even from Hubble Space Telescope images and radio interferometry measurements 
A)  rapid fluctuations in brightness since variations over 1 day mean that the source must be less than 1 light-day across 
B)  instant disappearance of the quasar when occulted by the Moon's edge as the Moon moves in front of a quasar, indicating a very small source size 
C)  sharpness of the emission lines in their optical spectra since motions within a large source would smear out the line shapes 
D)  extremely small size of the image of a quasar, even from Hubble Space Telescope images and radio interferometry measurements

The fluctuation time for the brightnesses of quasars can be as short as a

For gravitational lensing of a distant quasar to occur, the galaxy producing the lensing must

The observed characteristics of a quasar are a

The energy output per second of a typical quasar is equal to that emitted by the Sun in 200 years. How much energy is this? The Sun's luminosity is 3.8 * 10²⁶ watts.

Quasars appear to be

A BL Lacertae object is a(n)

Jets of gas coming from an AGN are associated with

Evidence obtained over the last few years indicates that a quasar is MOST likely

The intensity of radiation coming from an active galaxy

Most quasi-stellar objects (QSOs) produce their strongest emissions in which region of the electromagnetic spectrum?

Which of these objects is NOT classified as an active galaxy?

An astronomer is observing the radiation from a distant active galaxy and notices that the amplitude of the signal varies in strength regularly over a certain period. The maximum possible size for the source of this radiation can now be calculated from the

Which observations of the radiation from quasars indicate that quasars are physically very small objects compared with galaxies?

What is the relationship between the size of an object and the rate at which its radiant output can vary?

The closest quasar is Cygnus A, 635 million light-years away. What does the Hubble law give for its redshift?

Many bright radio sources at very large distances from the Sun appear to emit energy from two relatively widely spaced sources. What mechanism is thought to produce these double-radio emission regions?

What recent evidence seems to indicate that several nearby galaxies may contain supermassive black holes at their centers?

An electron moving in a magnetic field in space is forced to move in a spiral pattern. As it does so, it emits

All quasars appear to be

What observations convince astronomers that the energy source of a quasar is physically very small?

Discovering the Night Sky

Gravitation and the Motion of the Planets

Light and Telescopes

Atomic Physics and Spectra

Exoplanets and the Formation of Planetary Systems

Formation of the Solar System

Earth and the Moon

The Other Terrestrial Planets

The Outer Planets

Vagabonds of the Solar System

The Sun: Our Extraordinary Star

Characterizing Stars

The Lives of Stars From Birth Through Middle Age

The Death of Stars

Black Holes: Matters of Gravity

The Milky Way Galaxy

Galaxies

Cosmology

Astrobiology

Filters

Exam 18: Quasars and Other Active Galaxies

The fluctuation time for the brightnesses of quasars can be as short as a

For gravitational lensing of a distant quasar to occur, the galaxy producing the lensing must

The observed characteristics of a quasar are a

The energy output per second of a typical quasar is equal to that emitted by the Sun in 200 years. How much energy is this? The Sun's luminosity is 3.8 * 1026 watts.

Quasars appear to be

A BL Lacertae object is a(n)

Jets of gas coming from an AGN are associated with

Evidence obtained over the last few years indicates that a quasar is MOST likely

The intensity of radiation coming from an active galaxy

Most quasi-stellar objects (QSOs) produce their strongest emissions in which region of the electromagnetic spectrum?

Which of these objects is NOT classified as an active galaxy?

An astronomer is observing the radiation from a distant active galaxy and notices that the amplitude of the signal varies in strength regularly over a certain period. The maximum possible size for the source of this radiation can now be calculated from the

Which observations of the radiation from quasars indicate that quasars are physically very small objects compared with galaxies?

What is the relationship between the size of an object and the rate at which its radiant output can vary?

The closest quasar is Cygnus A, 635 million light-years away. What does the Hubble law give for its redshift?

Many bright radio sources at very large distances from the Sun appear to emit energy from two relatively widely spaced sources. What mechanism is thought to produce these double-radio emission regions?

What recent evidence seems to indicate that several nearby galaxies may contain supermassive black holes at their centers?

An electron moving in a magnetic field in space is forced to move in a spiral pattern. As it does so, it emits

All quasars appear to be

What observations convince astronomers that the energy source of a quasar is physically very small?

Discovering the Night Sky

Gravitation and the Motion of the Planets

Light and Telescopes

Atomic Physics and Spectra

Exoplanets and the Formation of Planetary Systems

Formation of the Solar System

Earth and the Moon

The Other Terrestrial Planets

The Outer Planets

Vagabonds of the Solar System

The Sun: Our Extraordinary Star

Characterizing Stars

The Lives of Stars From Birth Through Middle Age

The Death of Stars

Black Holes: Matters of Gravity

The Milky Way Galaxy

Galaxies

Cosmology

Astrobiology

Filters

The energy output per second of a typical quasar is equal to that emitted by the Sun in 200 years. How much energy is this? The Sun's luminosity is 3.8 * 10²⁶ watts.