Question 1

Why is a higher percentage of distant galaxies classified as AGNs compared with the percentage of galaxies around us locally?

Accepted Answer

More distant galaxies are seen at an ear

Question 2

How do we know that many elliptical galaxies contain significant amounts of dark matter?

Accepted Answer

Many elliptical galaxies are observed to

Question 3

What caused early astronomers to believe that our galaxy is only about 6,000 light-years across?

Accepted Answer

A)  Telescopes were not powerful enough to observe stars farther away. 
B)  Interstellar dust blocked visible light from stars farther away. 
C)  Stars farther away could not be resolved as individual objects. 
D)  Astronomers miscalculated the distances to stars, believing that the stars were 50 times closer than they actually were. 
E)  Astronomers assumed all red stars were faint main-sequence stars, and they confused them with the more luminous red giants. 
A)  Telescopes were not powerful enough to observe stars farther away. 
B)  Interstellar dust blocked visible light from stars farther away. 
C)  Stars farther away could not be resolved as individual objects. 
D)  Astronomers miscalculated the distances to stars, believing that the stars were 50 times closer than they actually were. 
E)  Astronomers assumed all red stars were faint main-sequence stars, and they confused them with the more luminous red giants.

Question 4

To be a standard candle, an object must have a known

Accepted Answer

A)  lifetime. 
B)  brightness. 
C)  luminosity. 
D)  distance. 
E)  mass. 
A)  lifetime. 
B)  brightness. 
C)  luminosity. 
D)  distance. 
E)  mass.

Question 5

Which of the galactic rotation curves in the figure below is closest to what is actually measured for galaxies?

Accepted Answer

A)  1 
B)  2 
C)  3 
D)  4 
E)  4 for ellipticals, 2 for spirals 
A)  1 
B)  2 
C)  3 
D)  4 
E)  4 for ellipticals, 2 for spirals

Question 6

If a galaxy has an apparent velocity of 700 km/s, what is its distance if the Hubble constant is assumed to be 70 km/s/Mpc?

Accepted Answer

A)  10 Mpc 
B)  70 Mpc 
C)  100 Mpc 
D)  700 Mpc 
E)  1,000 Mpc 
A)  10 Mpc 
B)  70 Mpc 
C)  100 Mpc 
D)  700 Mpc 
E)  1,000 Mpc

Question 7

What makes up the majority of the mass of an individual spiral galaxy?

Accepted Answer

A)  a central supermassive black hole 
B)  dark matter 
C)  massive O- and B-type stars 
D)  cold molecular gas clouds 
E)  low-mass G-, K-, and M-type stars 
A)  a central supermassive black hole 
B)  dark matter 
C)  massive O- and B-type stars 
D)  cold molecular gas clouds 
E)  low-mass G-, K-, and M-type stars

Question 8

What are the main components of an AGN?

Accepted Answer

The "anatomy" of a typical AGN

Question 9

For which galaxies would it be easiest to measure rotation curves?

Accepted Answer

A)  elliptical 
B)  face-on barred spirals 
C)  face-on normal spirals 
D)  face-on S0 galaxies 
E)  edge-on spirals 
A)  elliptical 
B)  face-on barred spirals 
C)  face-on normal spirals 
D)  face-on S0 galaxies 
E)  edge-on spirals

Question 10

Astronomers can determine the maximum size of a distant, luminous object by

Accepted Answer

A)  directly resolving it in a telescope only. 
B)  using trigonometric parallax. 
C)  timing the fluctuations in its luminosity. 
D)  looking for the amplitude of an oscillating Doppler shift. 
E)  using the phenomenon of radio wave diffraction. 
A)  directly resolving it in a telescope only. 
B)  using trigonometric parallax. 
C)  timing the fluctuations in its luminosity. 
D)  looking for the amplitude of an oscillating Doppler shift. 
E)  using the phenomenon of radio wave diffraction.

Question 11

How do astronomers know that AGNs are as small as our Solar System?

Accepted Answer

AGNs have been observed to vary dramatic

Question 12

The dark features in the HST image in the figure shown below indicate

Accepted Answer

A)  collections of cool stars. 
B)  clumps of dark matter. 
C)  copious amounts of dark energy. 
D)  large amounts of dust. 
E)  faulty pixels on the CCD camera. 
A)  collections of cool stars. 
B)  clumps of dark matter. 
C)  copious amounts of dark energy. 
D)  large amounts of dust. 
E)  faulty pixels on the CCD camera.

Question 13

What did Edwin Hubble study in the Andromeda Galaxy that proved it was an individual galaxy and not part of our own Milky Way?

Accepted Answer

A)  Cepheid stars 
B)  Type Ia supernovae 
C)  globular clusters 
D)  red giant stars 
E)  RR Lyrae variables 
A)  Cepheid stars 
B)  Type Ia supernovae 
C)  globular clusters 
D)  red giant stars 
E)  RR Lyrae variables

Question 14

According to Hubble's law, as the distance of a galaxy ________, its ________ increases.

Accepted Answer

A)  increases; luminosity 
B)  increases; recessional velocity 
C)  decreases; luminosity 
D)  decreases; recessional velocity 
E)  decreases; peculiar velocity 
A)  increases; luminosity 
B)  increases; recessional velocity 
C)  decreases; luminosity 
D)  decreases; recessional velocity 
E)  decreases; peculiar velocity

Question 15

Active star formation does not typically occur in elliptical galaxies because they

Accepted Answer

A)  rotate too fast. 
B)  contain little cold gas. 
C)  are too massive. 
D)  are too far away. 
E)  usually contain active nuclei. 
A)  rotate too fast. 
B)  contain little cold gas. 
C)  are too massive. 
D)  are too far away. 
E)  usually contain active nuclei.

Question 16

What is plotted on a rotation curve, and what can it tell us about a galaxy?

Accepted Answer

A rotation curve is a plot of the veloci

Question 17

The spectrum of a galaxy is observed to have an H$\alpha$ emission line at a wavelength of 856.3 nm.What is its distance if the Hubble constant is assumed to be 70 km/s/Mpc? (Note that the rest wavelength of the H$\alpha$ emission line is 656.3 nm.)

Accepted Answer

z = (@#LAT-DLM&_obs -@#LAT-DLM&_rest)/@#LAT-DLM& <

Question 18

How did Edwin Hubble definitively prove that "spiral nebulae" were individual galaxies that were separate from the Milky Way?

Accepted Answer

Hubble identified Cepheid variable stars

Question 19

The formation of the Solar System and the existence of AGNs both demonstrate the

Accepted Answer

A)  information gained from how luminosity varies with time. 
B)  high efficiency of nuclear fusion. 
C)  effects of accretion disks. 
D)  importance of living in the center of a galaxy. 
E)  existence of dark matter. 
A)  information gained from how luminosity varies with time. 
B)  high efficiency of nuclear fusion. 
C)  effects of accretion disks. 
D)  importance of living in the center of a galaxy. 
E)  existence of dark matter.

Question 20

What is the difference between a Seyfert galaxy and a normal spiral galaxy?

Accepted Answer

A Seyfert galaxy contains a luminous,sta

Exam 19: Galaxies

Why is a higher percentage of distant galaxies classified as AGNs compared with the percentage of galaxies around us locally?

How do we know that many elliptical galaxies contain significant amounts of dark matter?

What caused early astronomers to believe that our galaxy is only about 6,000 light-years across?

To be a standard candle, an object must have a known

Which of the galactic rotation curves in the figure below is closest to what is actually measured for galaxies?

If a galaxy has an apparent velocity of 700 km/s, what is its distance if the Hubble constant is assumed to be 70 km/s/Mpc?

What makes up the majority of the mass of an individual spiral galaxy?

What are the main components of an AGN?

For which galaxies would it be easiest to measure rotation curves?

Astronomers can determine the maximum size of a distant, luminous object by

How do astronomers know that AGNs are as small as our Solar System?

The dark features in the HST image in the figure shown below indicate

What did Edwin Hubble study in the Andromeda Galaxy that proved it was an individual galaxy and not part of our own Milky Way?

According to Hubble's law, as the distance of a galaxy ________, its ________ increases.

Active star formation does not typically occur in elliptical galaxies because they

What is plotted on a rotation curve, and what can it tell us about a galaxy?

The spectrum of a galaxy is observed to have an H α\alphaα emission line at a wavelength of 856.3 nm.What is its distance if the Hubble constant is assumed to be 70 km/s/Mpc? (Note that the rest wavelength of the H α\alphaα emission line is 656.3 nm.)

How did Edwin Hubble definitively prove that "spiral nebulae" were individual galaxies that were separate from the Milky Way?

The formation of the Solar System and the existence of AGNs both demonstrate the

What is the difference between a Seyfert galaxy and a normal spiral galaxy?

Thinking Like an Astronomer

Patterns in the Skymotions of Earth and the Moon

Motion of Astronomical Bodies

Gravity and Orbits

Light

The Tools of the Astronomer

The Formation of Planetary Systems

The Terrestrial Planets and Earths Moon

Atmospheres of the Terrestrial Planets

Worlds of Gas and Liquidthe Giant Planets

Planetary Moons and Rings

Dwarf Planets and Small Solar System Bodies

Taking the Measure of Stars

Our Starthe Sun

The Interstellar Medium and Star Formation

Evolution of Low-Mass Stars

Evolution of High-Mass Stars

Relativity and Black Holes

The Milky Waya Normal Spiral Galaxy

The Expanding Universe

Cosmology

Large-Scale Structure in the Universe

Life

Filters

According to Hubble's law, as the distance of a galaxy , its increases.

The spectrum of a galaxy is observed to have an H $\alpha$ emission line at a wavelength of 856.3 nm.What is its distance if the Hubble constant is assumed to be 70 km/s/Mpc? (Note that the rest wavelength of the H $\alpha$ emission line is 656.3 nm.)