Question 1

Type Ia supernovae are reliable distance indicators for distant galaxies. Which of the following is NOT a reason for this?

Accepted Answer

A) They occur in many galaxies. 
B) They are giant stars and can be detected at large distances. 
C) The intrinsic luminosity can be determined from the light curve. 
D) Their identity as Type Ia supernovae can be determined from their light curves. 
A) They occur in many galaxies. 
B) They are giant stars and can be detected at large distances. 
C) The intrinsic luminosity can be determined from the light curve. 
D) Their identity as Type Ia supernovae can be determined from their light curves. B

Question 2

Suppose that a particular galaxy is 400 million pc from Earth. What is the recessional velocity of this galaxy? Take the Hubble constant to be 73 km/s/Mpc.

Accepted Answer

A) 5.8 km/s 
B) 175,000 km/s 
C) 5.8 million km/s 
D) 29,200 km/s 
A) 5.8 km/s 
B) 175,000 km/s 
C) 5.8 million km/s 
D) 29,200 km/s D

Question 3

The Hubble law describes how two properties of distant galaxies are related to each other. What are these two properties?

Accepted Answer

A) distance and velocity of recession 
B) brightness and recession velocity 
C) brightness and the width of the 21-cm radio emission line of hydrogen 
D) distance and brightness 
A) distance and velocity of recession 
B) brightness and recession velocity 
C) brightness and the width of the 21-cm radio emission line of hydrogen 
D) distance and brightness A

Question 4

Over what distance does the Cepheid variable technique work? The faintest objects that can be photographed through the best telescopes have apparent magnitudes of about m = 30. Consider a bright Cepheid with an absolute magnitude of M = -2.4. At what distance could it just be seen?

Accepted Answer

A) 30 pc 
B) 30 kpc 
C) 30 Mpc 
D) 30 Gpc 
A) 30 pc 
B) 30 kpc 
C) 30 Mpc 
D) 30 Gpc

Question 5

What is the ratio of barred spirals to ordinary spirals in our universe?

Accepted Answer

A) 1:100, very few spirals are barred. 
B) 10:1 
C) 2:1 
D) 1:2 
A) 1:100, very few spirals are barred. 
B) 10:1 
C) 2:1 
D) 1:2

Question 6

Which of the following statements concerning spiral galaxies is TRUE and provides a possible reason for the differences between different classes of spiral galaxies Sa, Sb, and Sc?

Accepted Answer

A) The fraction of their total mass, which in the form of dust and gas is different; Sa has the lowest fraction whereas Sc has the highest. 
B) The rate of star formation in their central bulges is different; the rate is highest for Sa type and lowest for Sc type. 
C) The ratio of dust to gas in the interstellar medium is different in these types of galaxies; Sa has the most dust whereas Sc has the most gas. 
D) The fraction of their total mass, which in the form of dust and gas is different; Sa has the highest fraction whereas Sc has the lowest. 
A) The fraction of their total mass, which in the form of dust and gas is different; Sa has the lowest fraction whereas Sc has the highest. 
B) The rate of star formation in their central bulges is different; the rate is highest for Sa type and lowest for Sc type. 
C) The ratio of dust to gas in the interstellar medium is different in these types of galaxies; Sa has the most dust whereas Sc has the most gas. 
D) The fraction of their total mass, which in the form of dust and gas is different; Sa has the highest fraction whereas Sc has the lowest.

Question 7

An astronomer studying the spectrum of a distant galaxy finds that its recessional velocity is 14,000 km/s. What is the distance to the galaxy? Take the Hubble constant to be 73 km/s/Mpc.

Accepted Answer

A) 96 Mpc 
B) 959,000 Mpc 
C) 1918 Mpc 
D) 192 Mpc 
A) 96 Mpc 
B) 959,000 Mpc 
C) 1918 Mpc 
D) 192 Mpc

Question 8

The intrinsic brightness (represented by luminosity) of a Cepheid variable star compared to that of the Sun is:

Accepted Answer

A) several thousand times larger. 
B) significantly less. 
C) about 10 times larger. 
D) about the same. 
A) several thousand times larger. 
B) significantly less. 
C) about 10 times larger. 
D) about the same.

Question 9

The great debate involving the nature of the nebulae took place in the year:

Accepted Answer

A) 1794. 
B) 1885. 
C) 1920. 
D) 1954. 
A) 1794. 
B) 1885. 
C) 1920. 
D) 1954.

Question 10

Which one of the following does NOT seem to be a mechanism for disrupting spiral arms in galaxies?

Accepted Answer

A) tidal interactions as galaxies pass by each other 
B) natural evolution of spirals into ellipticals 
C) collisions of galaxies 
D) cessation of star formation 
A) tidal interactions as galaxies pass by each other 
B) natural evolution of spirals into ellipticals 
C) collisions of galaxies 
D) cessation of star formation

Question 11

Which observation of elliptical galaxies provides a measure of the relative motions of stars and of the degree of randomness of their motions within these galaxies?

Accepted Answer

A) the redshift of spectral lines in their spectra 
B) the broadening of spectral lines in their spectra 
C) the relative brightnesses of central bulges and extended disks of these galaxies 
D) the shapes of the galaxies 
A) the redshift of spectral lines in their spectra 
B) the broadening of spectral lines in their spectra 
C) the relative brightnesses of central bulges and extended disks of these galaxies 
D) the shapes of the galaxies

Question 12

The protogalaxies we observe when we look out 13 billion ly away display all of the following characteristics EXCEPT ONE. Which is the EXCEPTION?

Accepted Answer

A) small 
B) irregular 
C) widely separated in space 
D) blue 
A) small 
B) irregular 
C) widely separated in space 
D) blue

Question 13

The Hubble classification for a galaxy having a disk and central bulge, with a smooth light distribution but no spiral arms, is:

Accepted Answer

A) irregular. 
B) S0. 
C) SBa. 
D) E0. 
A) irregular. 
B) S0. 
C) SBa. 
D) E0.

Question 14

What is the Hubble law, if V is recession velocity, d is the distance to a galaxy, and H0 is a constant?

Accepted Answer

A) V = H0 = constant 
B) V = H0 d 
C) H0 V = d 
D) Vd = H0 
A) V = H0 = constant 
B) V = H0 d 
C) H0 V = d 
D) Vd = H0

Question 15

The Hubble classification for a spiral galaxy with a tiny central bulge and narrow, well-defined, loosely wound spiral arms is:

Accepted Answer

A) E0. 
B) SBa. 
C) Sa. 
D) Sc. 
A) E0. 
B) SBa. 
C) Sa. 
D) Sc.

Question 16

Large clouds of very hot gas that emit vast quantities of x rays are detected between the galaxies in rich clusters of galaxies. How has this gas been heated?

Accepted Answer

A) by the intense radiation from nearby galaxies 
B) by the compression of gas as it falls into an unseen supermassive black hole between the galaxies 
C) by the annihilation of antimatter in this region of space by matter ejected by nearby galaxies 
D) by the collision of two galaxies 
A) by the intense radiation from nearby galaxies 
B) by the compression of gas as it falls into an unseen supermassive black hole between the galaxies 
C) by the annihilation of antimatter in this region of space by matter ejected by nearby galaxies 
D) by the collision of two galaxies

Question 17

If the recessional speed of a galaxy is a significant fraction of the speed of light, each of the following expressions will be valid EXCEPT ONE. Which one is ONLY valid when the velocity is much less than the speed of light?

Accepted Answer

A) z = Δλ / λ0 
B) v = H0 d 
C) H0 = 73 (km/sec)/Mpc 
D) z = v/c 
A) z = Δλ / λ0 
B) v = H0 d 
C) H0 = 73 (km/sec)/Mpc 
D) z = v/c

Question 18

How does the number of barred spirals in the universe compare to the number of ordinary spirals?

Accepted Answer

A) Ordinary spirals outnumber barred spirals. 
B) The question is meaningless; barred spirals are simply ordinary spirals seen edge on. 
C) Barred spirals outnumber ordinary spirals. 
D) There are about equal numbers of barred spirals and ordinary spirals. 
A) Ordinary spirals outnumber barred spirals. 
B) The question is meaningless; barred spirals are simply ordinary spirals seen edge on. 
C) Barred spirals outnumber ordinary spirals. 
D) There are about equal numbers of barred spirals and ordinary spirals.

Question 19

On the basis of the distance to the Coma Cluster of galaxies (90 Mpc) and the Hubble relation, using for the Hubble constant H0 the value 73 km/sec per million pc, what would be the approximate wavelength shift of the Balmer H $\alpha$ spectral line at 656.3 nm emitted by a galaxy in the cluster because of the general expansion of the universe? (See Box 23-2, Universe, 11th ed.)

Accepted Answer

A) 1.44 × 10-2 nm 
B) 2.87 × 10-3 nm 
C) 143.7 nm 
D) 14.4 nm 
A) 1.44 × 10-2 nm 
B) 2.87 × 10-3 nm 
C) 143.7 nm 
D) 14.4 nm

Question 20

Our theories for the origin of spiral arms include each of the following EXCEPT ONE. Which is the EXCEPTION?

Accepted Answer

A) density waves 
B) self-propagating star formation 
C) the natural, gradual evolution from ellipticals into spirals 
D) interactions between galaxies 
A) density waves 
B) self-propagating star formation 
C) the natural, gradual evolution from ellipticals into spirals 
D) interactions between galaxies

Exam 23: Galaxies

Type Ia supernovae are reliable distance indicators for distant galaxies. Which of the following is NOT a reason for this?

Suppose that a particular galaxy is 400 million pc from Earth. What is the recessional velocity of this galaxy? Take the Hubble constant to be 73 km/s/Mpc.

The Hubble law describes how two properties of distant galaxies are related to each other. What are these two properties?

Over what distance does the Cepheid variable technique work? The faintest objects that can be photographed through the best telescopes have apparent magnitudes of about m = 30. Consider a bright Cepheid with an absolute magnitude of M = -2.4. At what distance could it just be seen?

What is the ratio of barred spirals to ordinary spirals in our universe?

Which of the following statements concerning spiral galaxies is TRUE and provides a possible reason for the differences between different classes of spiral galaxies Sa, Sb, and Sc?

An astronomer studying the spectrum of a distant galaxy finds that its recessional velocity is 14,000 km/s. What is the distance to the galaxy? Take the Hubble constant to be 73 km/s/Mpc.

The intrinsic brightness (represented by luminosity) of a Cepheid variable star compared to that of the Sun is:

The great debate involving the nature of the nebulae took place in the year:

Which one of the following does NOT seem to be a mechanism for disrupting spiral arms in galaxies?

Which observation of elliptical galaxies provides a measure of the relative motions of stars and of the degree of randomness of their motions within these galaxies?

The protogalaxies we observe when we look out 13 billion ly away display all of the following characteristics EXCEPT ONE. Which is the EXCEPTION?

The Hubble classification for a galaxy having a disk and central bulge, with a smooth light distribution but no spiral arms, is:

What is the Hubble law, if V is recession velocity, d is the distance to a galaxy, and H0 is a constant?

The Hubble classification for a spiral galaxy with a tiny central bulge and narrow, well-defined, loosely wound spiral arms is:

Large clouds of very hot gas that emit vast quantities of x rays are detected between the galaxies in rich clusters of galaxies. How has this gas been heated?

If the recessional speed of a galaxy is a significant fraction of the speed of light, each of the following expressions will be valid EXCEPT ONE. Which one is ONLY valid when the velocity is much less than the speed of light?

How does the number of barred spirals in the universe compare to the number of ordinary spirals?

Our theories for the origin of spiral arms include each of the following EXCEPT ONE. Which is the EXCEPTION?

Astronomy and the Universe

Knowing the Heavens

Eclipses and the Motion of the Moon

Gravitation and the Waltz of the Planets

The Nature of Light

Optics and Telescopes

Comparative Planetology I: Our Solar System

Comparative Planetology II: the Origin of Our Solar System

The Living Earth

Our Barren Moon

Mercury, Venus, and Mars: Terrestrial, yet Unique

Jupiter and Saturn: Lords of the Planets

Jupiter and Saturns Satellites of Fire and Ice

Uranus, Neptune, Pluto, and the Kuiper Belt: Remote Worlds

Asteroids, Comets, and Impacts

Our Star, the Sun

The Nature of the Stars

The Birth of Stars

Stellar Evolution: on and After the Main Sequence

Stellar Evolution: The Death of Stars

Stellar Remnants: Neutron Stars and Black Holes

Our Galaxy

Quasars and Active Galaxies

Cosmology: The Origin and Evolution of the Universe

Exploring the Early Universe

The Search for Extraterrestrial Life

Filters

What is the Hubble law, if V is recession velocity, d is the distance to a galaxy, and H₀ is a constant?