Question 1

What type of galaxy is shown in the figure below?

Accepted Answer

A)  a giant elliptical 
B)  a regular spiral galaxy 
C)  an irregular galaxy 
D)  a barred spiral 
E)  a dwarf spiral 
A)  a giant elliptical 
B)  a regular spiral galaxy 
C)  an irregular galaxy 
D)  a barred spiral 
E)  a dwarf spiral

Question 2

What is the most likely candidate for what composes the dark matter in galaxies?

Accepted Answer

The most likely source of the

Question 3

Astronomers use galactic redshift to estimate

Accepted Answer

A)  gravity. 
B)  luminosity. 
C)  star counts. 
D)  mass. 
E)  distance. 
A)  gravity. 
B)  luminosity. 
C)  star counts. 
D)  mass. 
E)  distance.

Question 4

How did Hubble classify galaxies? Is there any significance to this organization?

Accepted Answer

Elliptical galaxies are organized based

Question 5

Which distance indicator can be used to measure the most distant objects?

Accepted Answer

A)  Cepheids 
B)  parallax 
C)  Type Ia supernovae 
D)  main-sequence fitting 
E)  RR Lyrae stars 
A)  Cepheids 
B)  parallax 
C)  Type Ia supernovae 
D)  main-sequence fitting 
E)  RR Lyrae stars

Question 6

How do we know that AGNs have sizes on the order of our Solar System?

Accepted Answer

A)  Quasars and Seyfert galaxies are stellar-like sources. 
B)  Their brightness varies by factors of a few. 
C)  The emission lines in their spectra show gas rotating at speeds of thousands of km/s. 
D)  Their brightness varies on timescales ranging from hours to a day. 
E)  We can measure their angular size, which gives us the physical size when we know the distance. 
A)  Quasars and Seyfert galaxies are stellar-like sources. 
B)  Their brightness varies by factors of a few. 
C)  The emission lines in their spectra show gas rotating at speeds of thousands of km/s. 
D)  Their brightness varies on timescales ranging from hours to a day. 
E)  We can measure their angular size, which gives us the physical size when we know the distance.

Question 7

The spectrum of a galaxy is observed to have an H$\alpha$ emission line at a wavelength of 928.7 nm.What is its redshift? (Note that the rest wavelength of the H$\alpha$ emission line is 656.3 nm.)

Accepted Answer

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

Question 8

As of the writing of your textbook, what types of galaxies (not including our own Milky Way Galaxy) have been observed to have planets orbiting stars within them?

Accepted Answer

A)  other spiral galaxies only 
B)  elliptical galaxies only 
C)  irregular galaxies only 
D)  spiral, elliptical, and irregular galaxies 
E)  no planets have been observed in other galaxies. 
A)  other spiral galaxies only 
B)  elliptical galaxies only 
C)  irregular galaxies only 
D)  spiral, elliptical, and irregular galaxies 
E)  no planets have been observed in other galaxies.

Question 9

If the spectrum of a distant galaxy is observed to have a calcium K absorption line that occurs at a wavelength of 500.4 nm, what is this galaxy's distance if the rest wavelength of this absorption line is 393.4 nm? Assume the Hubble constant is 70 km/s/Mpc.

Accepted Answer

A)  720 Mpc 
B)  950 Mpc 
C)  1,200 Mpc 
D)  2,600 Mpc 
E)  3,700 Mpc 
A)  720 Mpc 
B)  950 Mpc 
C)  1,200 Mpc 
D)  2,600 Mpc 
E)  3,700 Mpc

Question 10

Elliptical galaxies appear red because they

Accepted Answer

A)  are moving away from us. 
B)  contain mostly ionized hydrogen gas. 
C)  contain mostly old stars. 
D)  contain lots of dust. 
E)  contain a mix of old and young stars. 
A)  are moving away from us. 
B)  contain mostly ionized hydrogen gas. 
C)  contain mostly old stars. 
D)  contain lots of dust. 
E)  contain a mix of old and young stars.

Question 11

The technique of using a star's spectrum to find its location on the H-R diagram, which provides an estimate of its luminosity, and thereby its distance, is called

Accepted Answer

A)  the Tully-Fisher method. 
B)  spectroscopic parallax. 
C)  the Doppler shift. 
D)  Hubble's law. 
E)  trigonometric parallax. 
A)  the Tully-Fisher method. 
B)  spectroscopic parallax. 
C)  the Doppler shift. 
D)  Hubble's law. 
E)  trigonometric parallax.

Question 12

The term "dark" in "dark matter" refers to the fact that dark matter

Accepted Answer

A)  absorbs but does not emit light. 
B)  emits only infrared light. 
C)  emits only ultraviolet ("black") light. 
D)  does not absorb or emit light. 
E)  absorbs 99 percent of all light, but emits only in radio waves. 
A)  absorbs but does not emit light. 
B)  emits only infrared light. 
C)  emits only ultraviolet ("black") light. 
D)  does not absorb or emit light. 
E)  absorbs 99 percent of all light, but emits only in radio waves.

Question 13

Even though each item on the distance ladder is only effective within a certain distance range, the concept is still effective because

Accepted Answer

A)  each technique produces exact distances on its own. 
B)  the distance ladder concept can be verified by looking in different wavelength ranges. 
C)  each step can be calibrated through its overlap with the previous step. 
D)  distances are ultimately relative, and not absolute. 
E)  the time delay due to light travel time is significant enough to limit the accuracy of distance measurements anyway. 
A)  each technique produces exact distances on its own. 
B)  the distance ladder concept can be verified by looking in different wavelength ranges. 
C)  each step can be calibrated through its overlap with the previous step. 
D)  distances are ultimately relative, and not absolute. 
E)  the time delay due to light travel time is significant enough to limit the accuracy of distance measurements anyway.

Question 14

Name two "rungs" in the distance ladder, and how distances within of these two "rungs" are measured or estimated.

Accepted Answer

Among the "rungs" are parallax (astromet

Question 15

The recession speed of spiral galaxies may also render their colors ________ due to ________.

Accepted Answer

A)  bluer; relativistic beaming 
B)  bluer; a Doppler-like effect 
C)  redder; relativistic beaming 
D)  redder; a Doppler-like effect 
E)  redder; galactic interactions 
A)  bluer; relativistic beaming 
B)  bluer; a Doppler-like effect 
C)  redder; relativistic beaming 
D)  redder; a Doppler-like effect 
E)  redder; galactic interactions

Question 16

You read about the discovery of quasars with redshift z larger than 1.This means that

Accepted Answer

A)  their host galaxies are receding at speeds exceeding the speed of light. 
B)  the measurements of redshift must be wrong; z cannot exceed 1. 
C)  the relationship between z and receding speed must account for relativistic corrections. 
D)  the speed of light can exceed c in the case of distant quasars. 
E)  quasars must contain a lot of dark matter. 
A)  their host galaxies are receding at speeds exceeding the speed of light. 
B)  the measurements of redshift must be wrong; z cannot exceed 1. 
C)  the relationship between z and receding speed must account for relativistic corrections. 
D)  the speed of light can exceed c in the case of distant quasars. 
E)  quasars must contain a lot of dark matter.

Question 17

Which of the following lists distance indicators from nearest to farthest?

Accepted Answer

A)  Cepheids, parallax, spectroscopic parallax, Type Ia supernovae 
B)  parallax, spectroscopic parallax, Cepheids, Type Ia supernovae 
C)  parallax, spectroscopic parallax, Type Ia supernovae, Cepheids 
D)  spectroscopic parallax, parallax, Cepheids, Type Ia supernovae 
E)  Cepheids, Type Ia supernovae, spectroscopic parallax, parallax 
A)  Cepheids, parallax, spectroscopic parallax, Type Ia supernovae 
B)  parallax, spectroscopic parallax, Cepheids, Type Ia supernovae 
C)  parallax, spectroscopic parallax, Type Ia supernovae, Cepheids 
D)  spectroscopic parallax, parallax, Cepheids, Type Ia supernovae 
E)  Cepheids, Type Ia supernovae, spectroscopic parallax, parallax

Question 18

Use the figure below to estimate the value of Hubble's constant.Be sure to include the appropriate units.

Accepted Answer

Hubble's constant is the slope of this l

Question 19

Explain why Hubble's law, which is linear, has no intercept (recall the standard equation for a line
is y = mx + b).

Accepted Answer

Hubble's law indicates that a zero dista

Question 20

Using the figure below, describe what each observer (labeled 1 through 3) would see in terms of the type of event and special features visible to that observer.

Accepted Answer

Observer 1 would see a relativistically

Exam 19: Galaxies

What type of galaxy is shown in the figure below?

What is the most likely candidate for what composes the dark matter in galaxies?

Astronomers use galactic redshift to estimate

How did Hubble classify galaxies? Is there any significance to this organization?

Which distance indicator can be used to measure the most distant objects?

How do we know that AGNs have sizes on the order of our Solar System?

The spectrum of a galaxy is observed to have an H α\alphaα emission line at a wavelength of 928.7 nm.What is its redshift? (Note that the rest wavelength of the H α\alphaα emission line is 656.3 nm.)

As of the writing of your textbook, what types of galaxies (not including our own Milky Way Galaxy) have been observed to have planets orbiting stars within them?

If the spectrum of a distant galaxy is observed to have a calcium K absorption line that occurs at a wavelength of 500.4 nm, what is this galaxy's distance if the rest wavelength of this absorption line is 393.4 nm? Assume the Hubble constant is 70 km/s/Mpc.

Elliptical galaxies appear red because they

The technique of using a star's spectrum to find its location on the H-R diagram, which provides an estimate of its luminosity, and thereby its distance, is called

The term "dark" in "dark matter" refers to the fact that dark matter

Even though each item on the distance ladder is only effective within a certain distance range, the concept is still effective because

Name two "rungs" in the distance ladder, and how distances within of these two "rungs" are measured or estimated.

The recession speed of spiral galaxies may also render their colors ________ due to ________.

You read about the discovery of quasars with redshift z larger than 1.This means that

Which of the following lists distance indicators from nearest to farthest?

Use the figure below to estimate the value of Hubble's constant.Be sure to include the appropriate units.

Explain why Hubble's law, which is linear, has no intercept (recall the standard equation for a line is y = mx + b).

Using the figure below, describe what each observer (labeled 1 through 3) would see in terms of the type of event and special features visible to that observer.

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

The spectrum of a galaxy is observed to have an H $\alpha$ emission line at a wavelength of 928.7 nm.What is its redshift? (Note that the rest wavelength of the H $\alpha$ emission line is 656.3 nm.)

The recession speed of spiral galaxies may also render their colors due to .