Question 1

Galaxies throughout the universe appear to be distributed:

Accepted Answer

A)  mostly in a single spherical shell surrounding a void in space presumed to have been caused by a vast explosion at the time of the Big Bang. 
B)  around a single point in space, the presumed location of the original Big Bang that created the universe. 
C)  in groups and surfaces surrounding vast voids, much like the surfaces of giant bubbles. 
D)  uniformly throughout space.

Question 2

Quasars appear to be:

Accepted Answer

A)  very distant, intrinsically bright objects moving in random directions at high speeds. 
B)  very distant, intrinsically faint objects with very high blueshifts in their spectra. 
C)  relatively close with very high redshifts. 
D)  very distant, intrinsically bright objects with very high redshifts

Question 3

A spiral galaxy is observed edge-on so that its spiral arms are barely visible.The galaxy,however,is observed to have a very large nuclear bulge.Thus,this galaxy:

Accepted Answer

A)  is probably type Sa. 
B)  is probably type Sb. 
C)  is probably type Sc. 
D)  cannot be classified if its spiral arms cannot be studied.

Question 4

What physical process has allowed astronomers to measure the overall number and distribution of brown dwarfs in the Milky Way Galaxy?

Accepted Answer

A)  The gravitational fields of brown dwarfs can bend the light from background stars. 
B)  Brown dwarfs emit copious amounts of infrared radiation, which can penetrate the interstellar medium. 
C)  Molecules in the atmospheres of brown dwarfs emit radio waves that can be detected from Earth. 
D)  Brown dwarfs occasionally eclipse (block the light from) more distant stars.

Question 5

Ans: C
Section: 13-9
-One difficulty with the density wave theory is that:

Accepted Answer

A)  the theory fails to explain why a given spiral pattern lasts only a small fraction of the lifetime of a galaxy. 
B)  the theory fails to provide a mechanism for star formation. 
C)  we are unsure of the mechanism that produces the energy output necessary to sustain the density wave. 
D)  the theory fails to explain the distribution of Population I and Population II stars in a galaxy.

Question 6

Quasars all appear to be:

Accepted Answer

A)  extremely massive objects in the Milky Way Galaxy, their spectra showing very high gravitational redshift. 
B)  moving away from us at very high speeds, up to about 90% of the speed of light. 
C)  moving across our line of sight at very high speeds, as seen in time-lapse photographs. 
D)  moving toward us at high speeds, as high as 90% of the speed of light.

Question 7

In 1785,William Herschel proposed that the solar system was at the center of the Milky Way Galaxy.How did he reach this conclusion?

Accepted Answer

A)  Like the ancient Greeks and many of their successors for over a thousand years, Herschel based his conclusion on the philosophical importance of Earth in the cosmos. 
B)  Herschel's observations suggested that the stars in the Milky Way Galaxy were distributed uniformly around Earth. 
C)  Herschel measured distances to globular clusters and determined that they were distributed uniformly around Earth. 
D)  Herschel determined that Cepheid variable stars in the Milky Way Galaxy were distributed uniformly around Earth.

Question 8

What useful purpose did variable stars serve for Harlow Shapley in locating the galactic center?

Accepted Answer

A)  Variable stars are important spiral arm tracers and thus defined the shape of the Milky Way Galaxy. 
B)  The brightness variations of variable stars allowed accurate distances to be measured. 
C)  Variable stars emit copious amounts of infrared radiation and are thus visible through interstellar dust that obscures visible light. 
D)  Variable stars are concentrated in the galactic center and so defined its direction.

Question 9

Which object typically has the greatest luminosity? (See Table 13-2,Comins,Discovering the Essential Universe,6th ed.)

Accepted Answer

A)  a giant elliptical galaxy 
B)  a Seyfert galaxy 
C)  a radio galaxy 
D)  a quasar

Question 10

How can astronomers determine the size of an emission region in a very distant and unresolvable source?

Accepted Answer

A)  by measuring the object's mass and using a reasonable value for the average density for matter to calculate its volume and hence its diameter 
B)  by using radio interferometry since this technique can resolve far greater detail than optical imaging 
C)  by measuring brightness variability since an object cannot vary more rapidly than the time taken for light to cross the source 
D)  by measuring the redshift of its spectrum since the redshift will depend on the source size

Question 11

What is microlensing?

Accepted Answer

A)  the minute shift in the apparent position of a star as an object passes in front of it 
B)  the slow brightening of a star as an object passes in front of it 
C)  the temporary disappearance of a star as an object passes in front of it 
D)  the gradual reduction in brightness of a star as an object passes in front of it

Question 12

Suppose we could examine a star and determine its apparent magnitude m without any intervening gas and dust.Compared with its apparent magnitude measured with gas and dust between us and the star,this "clean" measurement of m would be:

Accepted Answer

A)  a larger number. 
B)  a smaller number. 
C)  the same number. 
D)  either larger or smaller depending on the star's speed (toward or away).

Question 13

Quasars have now been detected in which the highest redshifts,if translated to "recession velocities," indicate motion away from the Milky Way Galaxy of:

Accepted Answer

A)  a large fraction of the speed of light. 
B)  speeds as large as 3 × 10³ km/s, or 1% of the speed of light. 
C)  about 1/10 of the speed of light. 
D)  speeds greater than the speed of light, indicating that the interpretation of redshifts in terms of velocity is faulty.

Question 14

Who won the Shapley-Curtis debate when it concluded in 1920?

Accepted Answer

A)  Shapley won. 
B)  Curtis won. 
C)  Both sides won in the sense that each successfully explained part of the data that were being debated. 
D)  Neither side won because there was no hard, reliable evidence to support either side.

Question 15

The central "engine" of an active galaxy appears to be:

Accepted Answer

A)  stars falling into a supermassive black hole, then their remnants being thrown out in all directions. 
B)  supernova explosions in an extremely dense star cluster at the center of the galaxy. 
C)  the violent merger of two galaxies in which the collision throws out jets of matter along the rotation axis of the larger galaxy. 
D)  a supermassive black hole at the center of an accretion disk and material being projected out perpendicular to the disk in both directions.

Question 16

What important role do Cepheid variables stars have in astronomy?

Accepted Answer

A)  distance measurements to distant galaxies 
B)  the determination of stellar luminosities 
C)  the determination of speeds of stars in galactic arms from the Doppler shift of their spectra 
D)  the keeping of accurate time

Question 17

An astronomer studying a distant cluster of galaxies finds that several of the galaxies are spiral-shaped,with a large nuclear region and tightly wound arms.How should the astronomer classify these galaxies?

Accepted Answer

A)  Sb 
B)  SBb 
C)  Sa 
D)  Sc

Question 18

A grand-design spiral of type SBa has all of the following EXCEPT:

Accepted Answer

A)  tightly wound spiral arms. 
B)  a central bar. 
C)  about 25% gas and dust. 
D)  a halo of globular clusters.

Question 19

The famous Curtis-Shapley debate in 1920 concerned which fundamental astronomical question in astronomy?

Accepted Answer

A)  whether all stars were like the Sun or fundamentally different 
B)  whether the spiral "nebulae" were part of the Milky Way Galaxy or more distant, separate entities 
C)  whether the universe was expanding outward in all directions 
D)  whether the Sun was at the center of the Milky Way Galaxy

Question 20

Variable stars such as Cepheid variables are used in what important measurement in astronomy?

Accepted Answer

A)  the measurement of the distances to stars 
B)  the measurement of the rotation speeds of galaxies 
C)  the measurement of the surface temperatures of stars 
D)  the keeping of accurate time

Exam 13: The Galaxies