Question 1

What is the evidence that fast radio bursts are extragalactic in origin?

Accepted Answer

A)  They occur in all directions, not just toward the disk of the Milky Way. 
B)  The burst periods are too small to be nearby objects. 
C)  The bursts are all redshifted. 
D)  The bursts are all very faint. 
A)  They occur in all directions, not just toward the disk of the Milky Way. 
B)  The burst periods are too small to be nearby objects. 
C)  The bursts are all redshifted. 
D)  The bursts are all very faint.

Question 2

Variations in the luminosity of quasars over the span of a few hours are an indication

Accepted Answer

A)  of the rapid rotation of the sources. 
B)  that these objects are actually binary systems in which one sees mutual eclipses. 
C)  of the relatively small size of the emitting regions. 
D)  of obscuring gas and dust clouds moving in front of them from Earth's point of view. 
A)  of the rapid rotation of the sources. 
B)  that these objects are actually binary systems in which one sees mutual eclipses. 
C)  of the relatively small size of the emitting regions. 
D)  of obscuring gas and dust clouds moving in front of them from Earth's point of view.

Question 3

Which of these is NOT a characteristic of active galaxies?

Accepted Answer

A)  jets 
B)  strong emission lines in the spectrum 
C)  Doppler shifts indicating a large rate of rotation 
D)  bright starlike nuclei 
A)  jets 
B)  strong emission lines in the spectrum 
C)  Doppler shifts indicating a large rate of rotation 
D)  bright starlike nuclei

Question 4

The energy-generation mechanism for active galaxies is believed to be

Accepted Answer

A)  large numbers of supernovae erupting simultaneously. 
B)  cosmic radioactive decay. 
C)  black holes colliding. 
D)  accretion disks around supermassive black holes. 
A)  large numbers of supernovae erupting simultaneously. 
B)  cosmic radioactive decay. 
C)  black holes colliding. 
D)  accretion disks around supermassive black holes.

Question 5

The surprising observational fact about quasars is that they appear to

Accepted Answer

A)  produce the energy output of greater than 100 galaxies in a volume similar to that of the solar system. 
B)  be the largest known structures in the universe, although they produce only modest amounts of energy. 
C)  be associated with ancient supernova explosions. 
D)  be moving rapidly toward Earth while emitting large amounts of energy. 
A)  produce the energy output of greater than 100 galaxies in a volume similar to that of the solar system. 
B)  be the largest known structures in the universe, although they produce only modest amounts of energy. 
C)  be associated with ancient supernova explosions. 
D)  be moving rapidly toward Earth while emitting large amounts of energy.

Question 6

Quasars, double-radio sources, and BL Lacertae objects may well be the same kind of object. The different appearance of them being simply that

Accepted Answer

A)  their position in the universe is different: Quasars are in the Milky Way Galaxy, double-radio sources are associated with other galaxies, and BL Lacertae objects are in the vast voids of space between galaxies. 
B)  the orientation of Earth's line of sight to the axis of their ejected jets of matter is different. 
C)  their ages are different: BL Lacertae objects evolving through the double-radio source phase end as quasars. 
D)  their sizes are different: Quasars are star-sized, double-radio sources are larger, and BL Lacertae objects are galaxy-sized. 
A)  their position in the universe is different: Quasars are in the Milky Way Galaxy, double-radio sources are associated with other galaxies, and BL Lacertae objects are in the vast voids of space between galaxies. 
B)  the orientation of Earth's line of sight to the axis of their ejected jets of matter is different. 
C)  their ages are different: BL Lacertae objects evolving through the double-radio source phase end as quasars. 
D)  their sizes are different: Quasars are star-sized, double-radio sources are larger, and BL Lacertae objects are galaxy-sized.

Question 7

What observational evidence seems to indicate the presence of a supermassive black hole at the center of the Milky Way's neighboring galaxy, M31, in Andromeda?

Accepted Answer

A)  slow but measurable motion of the Milky Way Galaxy toward M31 under the intense gravitational force of its black hole 
B)  very intense X-ray emission from a very small central core, indicating a very hot source 
C)  spectroscopic measurements of extremely high and symmetric Doppler shifts from stars orbiting rapidly around a massive object near the galactic center 
D)  small but dark region on detailed photographs of M31, showing an area from which light cannot escape 
A)  slow but measurable motion of the Milky Way Galaxy toward M31 under the intense gravitational force of its black hole 
B)  very intense X-ray emission from a very small central core, indicating a very hot source 
C)  spectroscopic measurements of extremely high and symmetric Doppler shifts from stars orbiting rapidly around a massive object near the galactic center 
D)  small but dark region on detailed photographs of M31, showing an area from which light cannot escape

Question 8

How has the number of quasars varied over the history of the universe?

Accepted Answer

A)  The number of quasars has remained approximately constant over time with new quasars being formed to replace those which deplete their fuel and die out. 
B)  Quasars were much more numerous 11 or 12 billion years ago, but since then the supermassive black holes in their centers have depleted their available gas and dust, their accretion disks have disappeared, and they are no longer quasars. 
C)  It takes billions of years to accumulate enough material to form a supermassive black hole, the heart of a quasar. Thus, the number of quasars has grown steadily as more and more supermassive black holes are formed. 
D)  The number of quasars has decreased steadily as they have evolved into other types of AGN like radio galaxies and BL Lacertae objects. 
A)  The number of quasars has remained approximately constant over time with new quasars being formed to replace those which deplete their fuel and die out. 
B)  Quasars were much more numerous 11 or 12 billion years ago, but since then the supermassive black holes in their centers have depleted their available gas and dust, their accretion disks have disappeared, and they are no longer quasars. 
C)  It takes billions of years to accumulate enough material to form a supermassive black hole, the heart of a quasar. Thus, the number of quasars has grown steadily as more and more supermassive black holes are formed. 
D)  The number of quasars has decreased steadily as they have evolved into other types of AGN like radio galaxies and BL Lacertae objects.

Question 9

A quasar is now thought to be a

Accepted Answer

A)  long-lived supernova explosion. 
B)  very luminous object at a very large distance from the Sun. 
C)  nearby star, ejected with great violence and velocity from the center of a galaxy. 
D)  distant but very luminous and active star in the Milky Way Galaxy. 
A)  long-lived supernova explosion. 
B)  very luminous object at a very large distance from the Sun. 
C)  nearby star, ejected with great violence and velocity from the center of a galaxy. 
D)  distant but very luminous and active star in the Milky Way Galaxy.

Question 10

Seyfert galaxies are

Accepted Answer

A)  elliptical galaxies with extremely bright nuclei. 
B)  supergiant elliptical galaxies that are periodically disturbed by supernova explosions within them. 
C)  spiral galaxies with extremely active cores. 
D)  active galaxies that shine mainly by radiation from two relatively widely spaced radio lobes. 
A)  elliptical galaxies with extremely bright nuclei. 
B)  supergiant elliptical galaxies that are periodically disturbed by supernova explosions within them. 
C)  spiral galaxies with extremely active cores. 
D)  active galaxies that shine mainly by radiation from two relatively widely spaced radio lobes.

Question 11

Quasars were originally thought to be stars in the Milky Way Galaxy. Which of these properties of quasars was LEAST unusual in comparison to normal stars?

Accepted Answer

A)  They were dim in the visible part of the spectrum. 
B)  They were very energetic in the radio part of the spectrum. 
C)  Their spectra were dominated by emission lines rather than absorption lines. 
D)  Their spectra showed patterns that were, at first, unrecognizable. 
A)  They were dim in the visible part of the spectrum. 
B)  They were very energetic in the radio part of the spectrum. 
C)  Their spectra were dominated by emission lines rather than absorption lines. 
D)  Their spectra showed patterns that were, at first, unrecognizable.

Question 12

Quasars typically appear to be

Accepted Answer

A)  extremely massive objects in the Milky Way Galaxy, their spectra showing very high gravitational redshift. 
B)  moving away from Earth at very high speeds, up to about 90% of the speed of light. 
C)  moving across Earth's line of sight at very high speeds, as seen in time-lapse photographs. 
D)  moving toward Earth at high speeds, as high as 90% of the speed of light. 
A)  extremely massive objects in the Milky Way Galaxy, their spectra showing very high gravitational redshift. 
B)  moving away from Earth at very high speeds, up to about 90% of the speed of light. 
C)  moving across Earth's line of sight at very high speeds, as seen in time-lapse photographs. 
D)  moving toward Earth at high speeds, as high as 90% of the speed of light.

Question 13

Which of these would NOT necessarily be categorized as "active galaxies"?

Accepted Answer

A)  radio galaxies 
B)  double-radio sources 
C)  BL Lacertae objects 
D)  galaxies with supermassive black holes 
A)  radio galaxies 
B)  double-radio sources 
C)  BL Lacertae objects 
D)  galaxies with supermassive black holes

Question 14

Faint starlike objects producing intense radio energy that eventually were called quasars were found to have an unusual feature in their optical spectra. This feature was

Accepted Answer

A)  an extreme redshift of emission lines that indicated high recessional velocities and hence great distances, requiring extremely high energy output to be detected. 
B)  a periodic variation of the Doppler shift from red to blue, indicating a light source oscillating back and forth over a few weeks. 
C)  two sets of spectral lines that indicated simultaneous motion of sources toward and away from the Sun, possibly from a rapidly expanding shell of material around the radio source. 
D)  an extreme blueshift, meaning that these stars in the Milky Way Galaxy were coming toward Earth at very high velocities. 
A)  an extreme redshift of emission lines that indicated high recessional velocities and hence great distances, requiring extremely high energy output to be detected. 
B)  a periodic variation of the Doppler shift from red to blue, indicating a light source oscillating back and forth over a few weeks. 
C)  two sets of spectral lines that indicated simultaneous motion of sources toward and away from the Sun, possibly from a rapidly expanding shell of material around the radio source. 
D)  an extreme blueshift, meaning that these stars in the Milky Way Galaxy were coming toward Earth at very high velocities.

Question 15

The specific characteristics that identify MOST quasars are

Accepted Answer

A)  that they look like elliptical galaxies but with high spectral redshifts. 
B)  luminous, starlike appearance, and very high spectral blueshift, indicating that they are approaching the Sun very fast, and rapid intensity fluctuations, indicating small intrinsic size. 
C)  luminous, starlike appearance with very high redshifts and hence very large distances, indicating very energetic sources. 
D)  spiral galaxy appearance and very high spectral blueshift, indicating that they are coming toward the Sun at high speed. 
A)  that they look like elliptical galaxies but with high spectral redshifts. 
B)  luminous, starlike appearance, and very high spectral blueshift, indicating that they are approaching the Sun very fast, and rapid intensity fluctuations, indicating small intrinsic size. 
C)  luminous, starlike appearance with very high redshifts and hence very large distances, indicating very energetic sources. 
D)  spiral galaxy appearance and very high spectral blueshift, indicating that they are coming toward the Sun at high speed.

Question 16

A starlike object seen on deep sky photographs coincides with an intense radio source and has a spectrum in which the characteristic Lyman pattern of hydrogen spectral lines has been shifted from the ultraviolet to the visible spectral range. What is this object?

Accepted Answer

A)  quasar 
B)  pulsar 
C)  supernova explosion 
D)  black hole 
A)  quasar 
B)  pulsar 
C)  supernova explosion 
D)  black hole

Question 17

Which observation of quasars convinced astronomers that quasars were very distant objects?

Accepted Answer

A)  extremely red spectrum, reddened by extreme interstellar absorption of the blue part of the spectrum, meaning that the source must be a very long way away 
B)  extreme redshift of visible Balmer and UV Lyman hydrogen emission lines, indicating high recessional velocities and hence, by the Hubble law, very large distances 
C)  extreme faintness at visible wavelengths; the inverse square law for visible light showed that they must be very distant 
D)  appearance as pointlike star images under the highest magnification, meaning that they must be very far away 
A)  extremely red spectrum, reddened by extreme interstellar absorption of the blue part of the spectrum, meaning that the source must be a very long way away 
B)  extreme redshift of visible Balmer and UV Lyman hydrogen emission lines, indicating high recessional velocities and hence, by the Hubble law, very large distances 
C)  extreme faintness at visible wavelengths; the inverse square law for visible light showed that they must be very distant 
D)  appearance as pointlike star images under the highest magnification, meaning that they must be very far away

Question 18

Suppose the X-ray signal from a quasar fluctuates with a period of 3 hours. What is the maximum size of the source?

Accepted Answer

A)  150,000 km, about the diameter of Jupiter 
B)  10.8 au, about the diameter of Jupiter's orbit 
C)  4.5 ly, about the distance between the Sun and the nearest star 
D)  10,800 ly, a tenth the size of the Milky Way Galaxy 
A)  150,000 km, about the diameter of Jupiter 
B)  10.8 au, about the diameter of Jupiter's orbit 
C)  4.5 ly, about the distance between the Sun and the nearest star 
D)  10,800 ly, a tenth the size of the Milky Way Galaxy

Question 19

Massive black holes have been discovered in the cores of what kinds of galaxies?

Accepted Answer

A)  giant elliptical only 
B)  spirals only 
C)  giant ellipticals and spirals only 
D)  dwarf ellipticals, giant ellipticals, and spirals 
A)  giant elliptical only 
B)  spirals only 
C)  giant ellipticals and spirals only 
D)  dwarf ellipticals, giant ellipticals, and spirals

Question 20

What is now considered to be the mechanism for the production of the double lobes of radio emission that appear on either side of many galaxies?

Accepted Answer

A)  radio emission from the two halves of galactic halos containing many globular clusters that generate radio noise 
B)  supernova explosion of a massive star and ejection outward in two opposite directions of very hot gas that emits thermal energy 
C)  two oppositely directed jets of relativistic particles spiraling around magnetic fields 
D)  material streaming in toward a black hole, perpendicular to and on opposite sides of the accretion disk 
A)  radio emission from the two halves of galactic halos containing many globular clusters that generate radio noise 
B)  supernova explosion of a massive star and ejection outward in two opposite directions of very hot gas that emits thermal energy 
C)  two oppositely directed jets of relativistic particles spiraling around magnetic fields 
D)  material streaming in toward a black hole, perpendicular to and on opposite sides of the accretion disk

What is the evidence that fast radio bursts are extragalactic in origin?

Variations in the luminosity of quasars over the span of a few hours are an indication

Which of these is NOT a characteristic of active galaxies?

The energy-generation mechanism for active galaxies is believed to be

The surprising observational fact about quasars is that they appear to

Quasars, double-radio sources, and BL Lacertae objects may well be the same kind of object. The different appearance of them being simply that

What observational evidence seems to indicate the presence of a supermassive black hole at the center of the Milky Way's neighboring galaxy, M31, in Andromeda?

How has the number of quasars varied over the history of the universe?

A quasar is now thought to be a

Seyfert galaxies are

Quasars were originally thought to be stars in the Milky Way Galaxy. Which of these properties of quasars was LEAST unusual in comparison to normal stars?

Quasars typically appear to be

Which of these would NOT necessarily be categorized as "active galaxies"?

Faint starlike objects producing intense radio energy that eventually were called quasars were found to have an unusual feature in their optical spectra. This feature was

The specific characteristics that identify MOST quasars are

A starlike object seen on deep sky photographs coincides with an intense radio source and has a spectrum in which the characteristic Lyman pattern of hydrogen spectral lines has been shifted from the ultraviolet to the visible spectral range. What is this object?

Which observation of quasars convinced astronomers that quasars were very distant objects?

Suppose the X-ray signal from a quasar fluctuates with a period of 3 hours. What is the maximum size of the source?

Massive black holes have been discovered in the cores of what kinds of galaxies?

What is now considered to be the mechanism for the production of the double lobes of radio emission that appear on either side of many galaxies?

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

What is the evidence that fast radio bursts are extragalactic in origin?

Variations in the luminosity of quasars over the span of a few hours are an indication

Which of these is NOT a characteristic of active galaxies?

The energy-generation mechanism for active galaxies is believed to be

The surprising observational fact about quasars is that they appear to

Quasars, double-radio sources, and BL Lacertae objects may well be the same kind of object. The different appearance of them being simply that

What observational evidence seems to indicate the presence of a supermassive black hole at the center of the Milky Way's neighboring galaxy, M31, in Andromeda?

How has the number of quasars varied over the history of the universe?

A quasar is now thought to be a

Seyfert galaxies are

Quasars were originally thought to be stars in the Milky Way Galaxy. Which of these properties of quasars was LEAST unusual in comparison to normal stars?

Quasars typically appear to be

Which of these would NOT necessarily be categorized as "active galaxies"?

Faint starlike objects producing intense radio energy that eventually were called quasars were found to have an unusual feature in their optical spectra. This feature was

The specific characteristics that identify MOST quasars are

A starlike object seen on deep sky photographs coincides with an intense radio source and has a spectrum in which the characteristic Lyman pattern of hydrogen spectral lines has been shifted from the ultraviolet to the visible spectral range. What is this object?

Which observation of quasars convinced astronomers that quasars were very distant objects?

Suppose the X-ray signal from a quasar fluctuates with a period of 3 hours. What is the maximum size of the source?

Massive black holes have been discovered in the cores of what kinds of galaxies?

What is now considered to be the mechanism for the production of the double lobes of radio emission that appear on either side of many galaxies?

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