Question 1

The Tully-Fisher relation (looking at rotation speeds) only works for:

Accepted Answer

A)  elliptical galaxies 
B)  the very closest galaxies, within a few dozen million light-years 
C)  galaxies that have a Type Ia supernova explosion in them 
D)  spiral galaxies 
E)  galaxies that we are observing from right around the time of the big bang

Question 2

Our Milky Way Galaxy is what type of galaxy?

Accepted Answer

A)  spiral 
B)  elliptical 
C)  dwarf elliptical 
D)  irregular 
E)  giant elliptical

Question 3

One of the main projects being carried out by the Hubble Space Telescope is to measure the distances of galaxies located in groups dozens of millions of lightyears away. What method do astronomers use with the Hubble to find such distances?

Accepted Answer

A)  constructing H-R diagrams 
B)  measuring the parallax over a period of a decade or so 
C)  finding Cepheid variables and measuring their periods 
D)  measuring the x-rays given off by the accretion disks around massive black holes 
E)  measuring the amount of dust in the disk of the galaxy

Question 4

Before you can use Hubble's Law to get the distance to a galaxy, what observation must you make of that galaxy?

Accepted Answer

A)  you must find a Cepheid variable star in the galaxy 
B)  you must take a spectrum of the galaxy and measure the red shift 
C)  you must measure how strongly the galaxy emits radio waves at a wavelength of 21 centimeters 
D)  you must find a Type Ia supernova that is exploding in that galaxy 
E)  all you need to do is look at the galaxy through any telescope

Question 5

If a galaxy contains a great deal of "dark matter," what will that do the galaxy's mass-to-light ratio?

Accepted Answer

A)  increase it a small amount 
B)  decrease it a small amount 
C)  increase it quite a bit 
D)  decrease it quite a bit 
E)  not affect it in any way (since it's dark matter)

Question 6

The new instrument that made it possible for Edwin Hubble to demonstrate the existence of other galaxies in the early 1920's was:

Accepted Answer

A)  the Hubble Space Telescope (that's why we named it after Hubble!) 
B)  the 300-ft radio telescope in West Virginia 
C)  a kind of electronic detector called a CCD 
D)  the 100-inch reflector on Mount Wilson 
E)  an infra-red telescope carried aboard one of the early airplane flights by the Wright Brothers
Section 26.2: Types of Galaxies

Question 7

Which is one reason that the typical galaxy's mass-to-light ratio (in units of the Sun's mass over the Sun's luminosity) generally greater than 1?

Accepted Answer

A)  galaxies contain mostly stars much brighter than the Sun 
B)  galaxies contain mostly stars much more massive than the Sun 
C)  galaxies contain many more stars that shine much less brightly than the Sun 
D)  most of the mass in a galaxy is in the form of dust 
E)  this is an unsolved problem in astronomy; scientists have no clue

Question 8

What method would astronomers use to find the distance to a galaxy so far away that individual stars are impossible to make out (resolve)?

Accepted Answer

A)  parallax 
B)  Cepheid variables 
C)  using the x-ray emission from the entire galaxy 
D)  finding the red?shift and using Hubble's Law 
E)  the turnoff point of the main sequence on an H-R diagram

Question 9

Which type of galaxy is observed to contain mostly older stars?

Accepted Answer

A)  spiral 
B)  elliptical 
C)  dwarf elliptical 
D)  irregular 
E)  none of the above

Question 10

Edwin Hubble developed a classification scheme for galaxies. By what characteristic did he classify galaxies?

Accepted Answer

A)  their brightness 
B)  their overall color 
C)  their shape 
D)  their abundance of the element iron 
E)  their Doppler Shift

Question 11

A graduate student in astronomy needs to measure the mass of a spiral galaxy she is studying for her PhD thesis. Which of the following observations would be important for her to make?

Accepted Answer

A)  determine whether or not there is evidence for a massive black hole at the galaxy's center 
B)  construct an H-R diagram for a prominent open cluster in the galaxy's disk 
C)  measure the gamma-ray emission from the galaxy 
D)  compare the overall color of the galaxy to other galaxies of the same type 
E)  obtain the speed at which stars or gas near the outer regions of the galaxy are moving around

Question 12

The first astronomer to show that spiral nebulae (today called spiral galaxies) have large Doppler shifts was

Accepted Answer

A)  Edwin Hubble 
B)  Vesto Slipher 
C)  Percival Lowell 
D)  Christian Doppler 
E)  Harlow Shapley

Question 13

The Tully-Fisher method for measuring the distance to galaxies relies on the observed relationship between the luminosity of a spiral galaxy and

Accepted Answer

A)  its rotational velocity (as determined from the width of the 21-cm line) 
B)  its number of high-energy sources (as determined from the total gamma-ray emission) 
C)  the size of its supernova remnants (as determined from radio maps) 
D)  the number of globular clusters (as determined from high-resolution images) 
E)  the number of companion galaxies found directly around it
Section 26.5: The Expanding Universe

Exam 26: Galaxies