Question 1

Which objects are NOT used as "standard candles" for distance measurement to distant galaxies?

Accepted Answer

A)  globular clusters 
B)  hot white dwarfs 
C)  supernova explosions 
D)  Cepheid variables

Question 2

What is the motion of stars in the bar across the inner part of the Milky Way Galaxy?

Accepted Answer

A)  The stars move along one side of the bar and then come back along the other side. 
B)  The stars oscillate back and forth along the bar, retracing the same path again and again. 
C)  The stars are part of a density wave which moves around the galactic center. The bar simply represents the place where stars and dust are most concentrated. 
D)  The stars basically remain stationary within the bar. The bar itself moves slowly around the galactic center, requiring more than 200 million years to orbit once.

Question 3

Which class of galaxy has the greatest range of sizes in the universe?

Accepted Answer

A)  irregular 
B)  elliptical 
C)  lenticular 
D)  spiral

Question 4

The Andromeda Galaxy (M31)is BEST described as a(n):

Accepted Answer

A)  extension of the Milky Way. 
B)  vortex surrounding a black hole. 
C)  gaseous nebula extending for 6° across our sky. 
D)  spiral collection of stars, dust, and gas 2 million ly away.

Question 5

Quasars were originally thought to be stars in our Galaxy.However,three of their properties listed below were unusual for an ordinary star.Which property was NOT unusual?

Accepted Answer

A)  They were dim in the visible part of the spectrum. 
B)  They were very energetic in the radio part of the spectrum. 
C)  Their spectra were dominated by emission lines rather than absorption lines. 
D)  Their spectra showed patterns which were, at first, unrecognizable.

Question 6

Which component of the Milky Way Galaxy accounts for interstellar extinction,the dimming of light from distant objects?

Accepted Answer

A)  cool hydrogen gas 
B)  so-called hidden or missing matter since its absorbing properties render it invisible in the Galaxy 
C)  molecules such as H₂ and CO, which are strong absorbers, in molecular clouds 
D)  dust

Question 7

A typical spiral galaxy has _____ stars in a disk of diameter _____ ly.

Accepted Answer

A)  10¹¹; 10⁵ 
B)  10¹¹; 1000 
C)  10⁹; 10⁶ 
D)  10⁶; 10⁵

Question 8

The Hubble flow,demonstrating the expansion of the universe,occurs:

Accepted Answer

A)  between galaxies in clusters, clusters in superclusters, and superclusters in wider regions of space. 
B)  only between superclusters of galaxies. 
C)  between stars in galaxies, galaxies in clusters, clusters in superclusters, and superclusters over wider regions of space. 
D)  between clusters of galaxies in superclusters and between superclusters over wider ranges of space.

Question 9

What are the typical characteristics of a quasar in terms of energy generation?

Accepted Answer

A)  output of 100 galaxies from a volume with diameter of 1 light-day 
B)  output of 10⁶ galaxies from a volume with diameter of 1 light-day 
C)  output of 100 galaxies from a volume with diameter of 1 light-year 
D)  output of single galaxy from a volume with diameter of 1 light-year

Question 10

Spiral galaxies with quasarlike nuclei are given the name Seyfert galaxies.Similarly,giant elliptical galaxies with quasarlike nuclei are called:

Accepted Answer

A)  radio galaxies. 
B)  peculiar galaxies. 
C)  head-tail source galaxies. 
D)  BL Lacertae objects.

Question 11

The fact that quasars can be detected from distances from which even the biggest and most luminous galaxies cannot be seen means that:

Accepted Answer

A)  they must be in directions where gravitational focusing by the masses of nearer galaxies makes them visible from Earth. 
B)  they must be far more luminous than the brightest galaxies. 
C)  they must be in directions where intergalactic absorption by dark matter is minimum, allowing us to see them. 
D)  their spectra have not been as redshifted by their motion as those of galaxies and hence they can still be seen.

Question 12

The significant feature of a Cepheid variable is that there is a relationship between two intrinsic parameters,one of which can be easily measured,while knowledge of the other parameter is required.These parameters are:

Accepted Answer

A)  period of brightness variation and spectral color. 
B)  variation of spectral color and distance to the star. 
C)  period of brightness variation and luminosity. 
D)  amplitude of brightness variation and luminosity.

Question 13

A supercluster of galaxies is a:

Accepted Answer

A)  cluster of galaxy clusters. 
B)  cluster of galaxies that is packed much more densely than normal clusters, giving it a higher mass. 
C)  phrase describing all the galaxies in the universe as a single system. 
D)  cluster of galaxies that is spread out over a larger than normal volume of space.

Question 14

The Sun's position in the Milky Way Galaxy is:

Accepted Answer

A)  unknown because our view is too severely restricted by interstellar dust. 
B)  in the disk of the Galaxy, inside a spiral arm or segment of a spiral arm. 
C)  in the disk of the Galaxy, between and well away from any spiral arm. 
D)  in the spherical halo, somewhat above and outside the spiral arms.

Question 15

What produces the arcs of light that appear to be centered on several clusters of galaxies,such as those shown in Figure 13-72 of Comins,Discovering the Essential Universe,6th ed.?

Accepted Answer

A)  These arcs represent the ends of plasma jets, where the material in the jets has been stopped as it ploughs into dark matter within the cluster of galaxies. 
B)  These arcs represent hot gas that is being heated by friction as it orbits a supermassive black hole in the center of the cluster of galaxies. 
C)  The arcs are reflections of light from the galaxies by sheets of intergalactic dust and gas, similar to the sundogs and halos around the Sun caused by ice crystal clouds. 
D)  The light from a single distant source is bent by the gravitational force of both the visible material and the dark matter of the intervening cluster of galaxies.

Question 16

Observational evidence of the existence of supermassive black holes in the centers of galaxies includes all of the following EXCEPT ONE.Which is the exception?

Accepted Answer

A)  The centers of these galaxies are completely dark, even though it is clear that the background (the other side of the galaxy) should be bright with stars. 
B)  Large amounts of energetic X rays are being emitted from the galactic centers. 
C)  Stars show very high speeds near the galactic centers. 
D)  The number density of stars near the galactic center is extraordinarily high.

Question 17

Suppose we could examine a star and determine its absolute magnitude M without any intervening gas and dust.Compared with its absolute 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 18

What type of object has been proposed to explain the tremendous activity detected at the center of the Milky Way Galaxy?

Accepted Answer

A)  a giant molecular cloud 
B)  a supermassive black hole 
C)  a supernova explosion 
D)  a rapidly rotating neutron star

Question 19

Many bright radio sources at very large distances from the Sun appear to emit energy from two relatively widely spaced sources.What mechanism is thought to produce these double-radio emission regions?

Accepted Answer

A)  Two oppositely directed beams of light and radio energy illuminate the intergalactic dust and gas. 
B)  Two oppositely directed plasma jets from a central source produce radio energy as the plasma slows down. 
C)  These sources are two galaxies orbiting each other like binary stars. 
D)  The sources are in fact a single source and its reflection in a dense intergalactic gas and dust "mirror," or plasma sheet.

Question 20

Which type of galaxy contains primarily Population II,metal-poor,low-mass,long-lived stars?

Accepted Answer

A)  elliptical 
B)  barred spiral 
C)  starburst 
D)  flocculent spiral

Exam 13: The Galaxies