Question 1

The Milky Way is an example of which type of galaxy?

Accepted Answer

A)  spiral 
B)  irregular 
C)  lenticular, S0 type 
D)  elliptical 
A)  spiral 
B)  irregular 
C)  lenticular, S0 type 
D)  elliptical

Question 2

A spiral galaxy is observed edge-on so that the spiral arms cannot be seen clearly.Is it possible to classify this galaxy using the Hubble classification scheme?

Accepted Answer

A)  Yes. The classification scheme is also an evolutionary scheme. It is possible to classify galaxies by age, for example, by counting the number of blue supergiants visible along the edge. 
B)  Yes. The tightness of spiral arms is correlated with the size of the nuclear bulge. 
C)  Yes. The tightness of spiral arms is correlated with the number of bright H II regions that can be counted along the edge. 
D)  No. The classification scheme is based upon the tightness of spiral arms. If the arms cannot be seen, the galaxy cannot be classified. 
A)  Yes. The classification scheme is also an evolutionary scheme. It is possible to classify galaxies by age, for example, by counting the number of blue supergiants visible along the edge. 
B)  Yes. The tightness of spiral arms is correlated with the size of the nuclear bulge. 
C)  Yes. The tightness of spiral arms is correlated with the number of bright H II regions that can be counted along the edge. 
D)  No. The classification scheme is based upon the tightness of spiral arms. If the arms cannot be seen, the galaxy cannot be classified.

Question 3

How has the maximum intrinsic brightness (minimum absolute magnitude)of Type Ia supernovae been measured?

Accepted Answer

A)  The distances to nearby Type Ia supernovae have been measured using trigonometric parallax. 
B)  Type Ia supernovae have been observed in distant galaxies in which Cepheid variables have also been observed. 
C)  The brightnesses of Type Ia supernovae have been measured at several different wavelengths, from which their temperature and hence their intrinsic brightnesses can be calculated. 
D)  The brightnesses of several Type Ia supernovae have been accurately measured relative to the brightnesses of the original stars before they exploded. 
A)  The distances to nearby Type Ia supernovae have been measured using trigonometric parallax. 
B)  Type Ia supernovae have been observed in distant galaxies in which Cepheid variables have also been observed. 
C)  The brightnesses of Type Ia supernovae have been measured at several different wavelengths, from which their temperature and hence their intrinsic brightnesses can be calculated. 
D)  The brightnesses of several Type Ia supernovae have been accurately measured relative to the brightnesses of the original stars before they exploded.

Question 4

The mass of the presently observable matter in a typical rich cluster of galaxies appears to be approximately what fraction of the mass required to hold the cluster together by gravity?

Accepted Answer

A)  10% 
B)  100%, or the entire galaxy 
C)  about 1% 
D)  90% 
A)  10% 
B)  100%, or the entire galaxy 
C)  about 1% 
D)  90%

Question 5

The mechanism that appears to generate two extensive regions of radio emission near active galaxies is:

Accepted Answer

A)  two very hot gas clouds, suspended by magnetic fields above the rotation axis of a galaxy, emitting 21-cm radio waves. 
B)  a radio source split by a dark absorbing disk across its center as seen from Earth. 
C)  the double image of a single source behind the galaxy produced by gravitational lensing by the galaxy. 
D)  two oppositely directed jets of energetic particles that collide with intergalactic gas. 
A)  two very hot gas clouds, suspended by magnetic fields above the rotation axis of a galaxy, emitting 21-cm radio waves. 
B)  a radio source split by a dark absorbing disk across its center as seen from Earth. 
C)  the double image of a single source behind the galaxy produced by gravitational lensing by the galaxy. 
D)  two oppositely directed jets of energetic particles that collide with intergalactic gas.

Question 6

The stellar components of the Milky Way Galaxy that act as tracers for the mapping of spiral-arm structure in the Galaxy are:

Accepted Answer

A)  bright Population I stars and emission nebulae surrounding them. 
B)  globular clusters. 
C)  supernova explosions since they are very luminous and can be seen through considerable dust and gas. 
D)  old red giant stars and white dwarfs. 
A)  bright Population I stars and emission nebulae surrounding them. 
B)  globular clusters. 
C)  supernova explosions since they are very luminous and can be seen through considerable dust and gas. 
D)  old red giant stars and white dwarfs.

Question 7

The positrons emitted from the galactic center can be detected because they annihilate with electrons and emit gamma rays.Two gamma rays are produced in such a situation to conserve both energy and momentum.Suppose the positron and electron,each with energy mc²,convert all of this energy into two identical gamma ray photons.What will be the wavelength of these photons?

Accepted Answer

A)  1.5 × 10-² nm 
B)  2.4 × 10-³ nm 
C)  3.9 × 10-⁴ nm 
D)  7.9 × 10-⁵ nm 
A)  1.5 × 10-² nm 
B)  2.4 × 10-³ nm 
C)  3.9 × 10-⁴ nm 
D)  7.9 × 10-⁵ nm

Question 8

How does the amount of dust and gas in a spiral galaxy vary with the classification of the galaxy?

Accepted Answer

A)  The most loosely wound galaxy, Sc, has the most dust and gas in its arms. 
B)  All spiral galaxies-Sa, Sb, and Sc types-have about the same fraction of gas and dust within them, about 4% by mass. 
C)  Only the most tightly wound spiral galaxies, type Sa, have any dust or gas in them at all. 
D)  The most loosely wound galaxy, Sc, has the least dust and gas in its arms. 
A)  The most loosely wound galaxy, Sc, has the most dust and gas in its arms. 
B)  All spiral galaxies-Sa, Sb, and Sc types-have about the same fraction of gas and dust within them, about 4% by mass. 
C)  Only the most tightly wound spiral galaxies, type Sa, have any dust or gas in them at all. 
D)  The most loosely wound galaxy, Sc, has the least dust and gas in its arms.

Question 9

What appear to be the characteristics of the object at the center of the Milky Way Galaxy?

Accepted Answer

A)  20 solar masses in a volume the size of the Sun 
B)  several trillion solar masses in a volume 2 ly in diameter 
C)  4 million solar masses in a volume the size of the solar system 
D)  5 billion solar masses in a volume smaller then Jupiter's orbit 
A)  20 solar masses in a volume the size of the Sun 
B)  several trillion solar masses in a volume 2 ly in diameter 
C)  4 million solar masses in a volume the size of the solar system 
D)  5 billion solar masses in a volume smaller then Jupiter's orbit

Question 10

Astronomers initially had difficulty identifying the emission lines in quasar spectra at optical wavelengths because:

Accepted Answer

A)  the emission lines were smeared out by the extremely high speed of the quasars, making them hard to measure. 
B)  the emission lines were from ionized atoms that had not been seen before. 
C)  the emission lines were found to be created from elements that do not exist on Earth. 
D)  no one expected to see the pattern of spectral lines characteristic of the ultraviolet hydrogen spectra in the visible region. 
A)  the emission lines were smeared out by the extremely high speed of the quasars, making them hard to measure. 
B)  the emission lines were from ionized atoms that had not been seen before. 
C)  the emission lines were found to be created from elements that do not exist on Earth. 
D)  no one expected to see the pattern of spectral lines characteristic of the ultraviolet hydrogen spectra in the visible region.

Question 11

Astronomer A claims that the Hubble constant is 84 km/s per Mpc,while astronomer B claims that it is 63 km/s per Mpc.If,using the Hubble constant,astronomer A claims that a particular galaxy is 4 billion ly away,then astronomer B would claim that it is _____ billion ly away.

Accepted Answer

A)  3 
B)  5.3 
C)  6 
D)  2 
A)  3 
B)  5.3 
C)  6 
D)  2

Question 12

If the galactic center of the Milky Way is now thought to contain a supermassive black hole,why is the Sun not falling into it under the black hole's extreme gravity?

Accepted Answer

A)  The Sun's mass is so small that even the extreme mass concentration at the galactic center will not exert a significant force on it. 
B)  The inward force exerted on the Sun from the black hole is offset by the force exerted outward by the hidden "dark" matter beyond the Sun's orbit. 
C)  The mutual gravitational forces of local stars in the Orion spiral arm are sufficient to overcome the strong inward force and keep the Sun moving in its orbit. 
D)  The Sun has sufficient velocity that it can orbit the galactic center in a circle. 
A)  The Sun's mass is so small that even the extreme mass concentration at the galactic center will not exert a significant force on it. 
B)  The inward force exerted on the Sun from the black hole is offset by the force exerted outward by the hidden "dark" matter beyond the Sun's orbit. 
C)  The mutual gravitational forces of local stars in the Orion spiral arm are sufficient to overcome the strong inward force and keep the Sun moving in its orbit. 
D)  The Sun has sufficient velocity that it can orbit the galactic center in a circle.

Question 13

The nearest quasar is:

Accepted Answer

A)  in the Milky Way Galaxy. 
B)  in the Local Group of galaxies. 
C)  among the nearby superclusters of galaxies. 
D)  barely visible at the remote edge of the observable universe. 
A)  in the Milky Way Galaxy. 
B)  in the Local Group of galaxies. 
C)  among the nearby superclusters of galaxies. 
D)  barely visible at the remote edge of the observable universe.

Question 14

The total number of galaxies in a rich,regular cluster of galaxies such as the Coma cluster is believed to be:

Accepted Answer

A)  about 10,000. 
B)  over 1 million. 
C)  about 1000. 
D)  several dozen. 
A)  about 10,000. 
B)  over 1 million. 
C)  about 1000. 
D)  several dozen.

Question 15

The Hubble distance-velocity relationship states that:

Accepted Answer

A)  all galaxies are being repelled from the central "engine" of the universe, with the ones closest to the center traveling fastest. 
B)  all galaxies are being pulled toward a central gravitational attractor in the universe, with the ones closest to the center traveling fastest. 
C)  the more distant a galaxy is from the Sun, the faster it is traveling toward the Sun. 
D)  the more distant a galaxy is from the Sun, the faster it is traveling away from the Sun. 
A)  all galaxies are being repelled from the central "engine" of the universe, with the ones closest to the center traveling fastest. 
B)  all galaxies are being pulled toward a central gravitational attractor in the universe, with the ones closest to the center traveling fastest. 
C)  the more distant a galaxy is from the Sun, the faster it is traveling toward the Sun. 
D)  the more distant a galaxy is from the Sun, the faster it is traveling away from the Sun.

Question 16

The method Hubble used to determine the distance to the Andromeda Galaxy (M31),thereby establishing the concept of separate and individual galaxies throughout the universe,was the:

Accepted Answer

A)  observation of Cepheid variable stars. 
B)  measurement of the redshift of the whole galaxy. 
C)  measurement of stellar parallax, or apparent motion, of stars because of Earth's orbital motion. 
D)  observation of the brightnesses of novae. 
A)  observation of Cepheid variable stars. 
B)  measurement of the redshift of the whole galaxy. 
C)  measurement of stellar parallax, or apparent motion, of stars because of Earth's orbital motion. 
D)  observation of the brightnesses of novae.

Question 17

In its orbit around the center of the Milky Way Galaxy,the Sun moves a distance equal to the diameter of Earth in a time of about:

Accepted Answer

A)  1 second. 
B)  1 minute. 
C)  1 day. 
D)  1 hour. 
A)  1 second. 
B)  1 minute. 
C)  1 day. 
D)  1 hour.

Question 18

Radio waves of 21-cm wavelength originate from which component of the interstellar medium?

Accepted Answer

A)  cool, neutral atomic hydrogen 
B)  cold molecular hydrogen, H₂ 
C)  cool carbon monoxide, CO 
D)  hot, ionized atomic hydrogen 
A)  cool, neutral atomic hydrogen 
B)  cold molecular hydrogen, H₂ 
C)  cool carbon monoxide, CO 
D)  hot, ionized atomic hydrogen

Question 19

The energy output per second of a typical quasar is equal to that emitted by the Sun in:

Accepted Answer

A)  1 year. 
B)  its whole lifetime. 
C)  200 years. 
D)  1 million years. 
A)  1 year. 
B)  its whole lifetime. 
C)  200 years. 
D)  1 million years.

Question 20

What is the dilemma about the spiral-arm structure of a typical spiral galaxy?

Accepted Answer

A)  The measured speeds of stars in the galaxy are exactly correct for the present spiral structure, having spun the observed tightness of the spiral in the typical lifetime of a galaxy. 
B)  If the measured speeds of stars in the galaxy had spun the arms into shape, these arms would be far less tightly wound than the observed arms. 
C)  If the measured speeds of stars in the galaxy had spun the arms into shape, these arms would be far more tightly wound than the observed arms. 
D)  The measured speeds of material in the spiral arms should not have led to any spiral but should have generated a straight bar rotating like a solid object. 
A)  The measured speeds of stars in the galaxy are exactly correct for the present spiral structure, having spun the observed tightness of the spiral in the typical lifetime of a galaxy. 
B)  If the measured speeds of stars in the galaxy had spun the arms into shape, these arms would be far less tightly wound than the observed arms. 
C)  If the measured speeds of stars in the galaxy had spun the arms into shape, these arms would be far more tightly wound than the observed arms. 
D)  The measured speeds of material in the spiral arms should not have led to any spiral but should have generated a straight bar rotating like a solid object.

The Milky Way is an example of which type of galaxy?

A spiral galaxy is observed edge-on so that the spiral arms cannot be seen clearly.Is it possible to classify this galaxy using the Hubble classification scheme?

How has the maximum intrinsic brightness (minimum absolute magnitude)of Type Ia supernovae been measured?

The mass of the presently observable matter in a typical rich cluster of galaxies appears to be approximately what fraction of the mass required to hold the cluster together by gravity?

The mechanism that appears to generate two extensive regions of radio emission near active galaxies is:

The stellar components of the Milky Way Galaxy that act as tracers for the mapping of spiral-arm structure in the Galaxy are:

How does the amount of dust and gas in a spiral galaxy vary with the classification of the galaxy?

What appear to be the characteristics of the object at the center of the Milky Way Galaxy?

Astronomers initially had difficulty identifying the emission lines in quasar spectra at optical wavelengths because:

Astronomer A claims that the Hubble constant is 84 km/s per Mpc,while astronomer B claims that it is 63 km/s per Mpc.If,using the Hubble constant,astronomer A claims that a particular galaxy is 4 billion ly away,then astronomer B would claim that it is _____ billion ly away.

If the galactic center of the Milky Way is now thought to contain a supermassive black hole,why is the Sun not falling into it under the black hole's extreme gravity?

The nearest quasar is:

The total number of galaxies in a rich,regular cluster of galaxies such as the Coma cluster is believed to be:

The Hubble distance-velocity relationship states that:

The method Hubble used to determine the distance to the Andromeda Galaxy (M31),thereby establishing the concept of separate and individual galaxies throughout the universe,was the:

In its orbit around the center of the Milky Way Galaxy,the Sun moves a distance equal to the diameter of Earth in a time of about:

Radio waves of 21-cm wavelength originate from which component of the interstellar medium?

The energy output per second of a typical quasar is equal to that emitted by the Sun in:

What is the dilemma about the spiral-arm structure of a typical spiral galaxy?

Discovering the Night Sky

Gravitation and the Waltz of the Planets

Light and Telescopes

Formation of the Solar System and Other Planetary Systems

Exoplanets

The Terrestrial Planets and Their Moons

The Outer Planets and Their Moons

Vagabonds of the Solar System

The Sun: Our Extraordinary Ordinary Star

Characterizing Stars

The Lives of the Stars From Birth Through Middle Age

The Deaths and Remnants of Stars

Cosmology

Astrobiology

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Exam 13: The Galaxies

The Milky Way is an example of which type of galaxy?

A spiral galaxy is observed edge-on so that the spiral arms cannot be seen clearly.Is it possible to classify this galaxy using the Hubble classification scheme?

How has the maximum intrinsic brightness (minimum absolute magnitude)of Type Ia supernovae been measured?

The mass of the presently observable matter in a typical rich cluster of galaxies appears to be approximately what fraction of the mass required to hold the cluster together by gravity?

The mechanism that appears to generate two extensive regions of radio emission near active galaxies is:

The stellar components of the Milky Way Galaxy that act as tracers for the mapping of spiral-arm structure in the Galaxy are:

How does the amount of dust and gas in a spiral galaxy vary with the classification of the galaxy?

What appear to be the characteristics of the object at the center of the Milky Way Galaxy?

Astronomers initially had difficulty identifying the emission lines in quasar spectra at optical wavelengths because:

Astronomer A claims that the Hubble constant is 84 km/s per Mpc,while astronomer B claims that it is 63 km/s per Mpc.If,using the Hubble constant,astronomer A claims that a particular galaxy is 4 billion ly away,then astronomer B would claim that it is _____ billion ly away.

If the galactic center of the Milky Way is now thought to contain a supermassive black hole,why is the Sun not falling into it under the black hole's extreme gravity?

The nearest quasar is:

The total number of galaxies in a rich,regular cluster of galaxies such as the Coma cluster is believed to be:

The Hubble distance-velocity relationship states that:

The method Hubble used to determine the distance to the Andromeda Galaxy (M31),thereby establishing the concept of separate and individual galaxies throughout the universe,was the:

In its orbit around the center of the Milky Way Galaxy,the Sun moves a distance equal to the diameter of Earth in a time of about:

Radio waves of 21-cm wavelength originate from which component of the interstellar medium?

The energy output per second of a typical quasar is equal to that emitted by the Sun in:

What is the dilemma about the spiral-arm structure of a typical spiral galaxy?

Discovering the Night Sky

Gravitation and the Waltz of the Planets

Light and Telescopes

Formation of the Solar System and Other Planetary Systems

Exoplanets

The Terrestrial Planets and Their Moons

The Outer Planets and Their Moons

Vagabonds of the Solar System

The Sun: Our Extraordinary Ordinary Star

Characterizing Stars

The Lives of the Stars From Birth Through Middle Age

The Deaths and Remnants of Stars

Cosmology

Astrobiology

Filters