Question 1

Which of the following is an important starting assumption in models of galaxy formation?

Accepted Answer

A) Black holes form first, seeding the formation of galaxies. 
B) All galaxies start out as spiral galaxies. 
C) Galaxies form first, then black holes. 
D) Some regions in the universe start out denser than others.

Question 2

What makes white- dwarf supernovae very good standard candles for distance measurements?

Accepted Answer

A) They are very bright, so they can be used to determine the distances to galaxies billions of light- years away. 
B) They should all have approximately the same luminosity. 
C) We have had several occur close to us in the Milky Way, so we have been able to determine their luminosities very accurately. 
D) They occur so frequently that we can use them to measure the distances to virtually all galaxies. 
E) both A and B

Question 3

Which of the following features is not a feature of central dominant galaxies?

Accepted Answer

A) They are often spiral galaxies. 
B) They often have multiple galactic nuclei near their centers. 
C) They are thought to form by the merger of several smaller galaxies. 
D) They're found in clusters of galaxies.

Question 4

The Redshift Controversy: The early debate on whether or not quasar redshifts were correctly interpreted by Hubble's Law (to indicate that quasars lay at enormous distances)is an excellent example of how a scientific debate was (reasonably)quickly settled by appeals to the observational evidence. Outline all of the observational evidence that quasars are indeed associated with the nuclei of distant galaxies and, therefore, their redshifts can be correctly interpreted using Hubble's Law.

Accepted Answer

The answer of The Redshift Controversy: The early debate on...

Question 5

Use the graph above showing data for the brightest galaxies in clusters of galaxies to answer the following questions. Which statement describes this graph?

Accepted Answer

A) The more distant the galaxy, the redder it is, but there are some exceptions. 
B) The more distant the galaxy, the bluer it is, but there are some exceptions. 
C) There is no trend because there are some exceptions.

Question 6

Which of the following statements is an explanation, not an observation?

Accepted Answer

A) Stars shine with energy generated by nuclear fusion in their cores. 
B) More distant galaxies are moving away from us faster than nearby galaxies. 
C) Stars can shine brightly for millions of years. 
D) All planets orbit the Sun in the same direction and in nearly the same plane.

Question 7

A star that is known to be 10,000 times brighter than the sun has the same apparent brightness as a nearby G2 star. How many times further away is the bright star?

Accepted Answer

A) The bright star is 10,000 times further away than the nearby G2 star. 
B) The bright star is 10 times further away than the nearby G2 star. 
C) The bright star is 100 times further away than the nearby G2 star. 
D) The bright star is actually a factor of 10 times closer than the nearby G2 star.

Question 8

Molly measures a Hubble constant of 20 km/sec/million light- years. Sam measures a Hubble constant of 25 km/sec/million light- years. All other assumptions being the same, which person would estimate a LARGER age to the universe?

Accepted Answer

A) Sam 
B) Molly 
C) They both would measure the same age.

Question 9

Current estimates place the age of the universe at about .

Accepted Answer

A) 10 million years 
B) 10 billion years 
C) 4 1/2 billion years 
D) 14 billion years

Question 10

Which of the following processes slowed the collapse of protogalactic clouds?

Accepted Answer

A) the radiating away of thermal energy 
B) the formation of the first generation of stars 
C) the shock waves from the exploding supernovae of the earliest stars 
D) the pull of gravity of the mass of the cloud material 
E) the conversion of gravitational potential energy into kinetic and thermal energy as the cloud collapsed

Question 11

A protogalactic cloud with slow star formation is more likely to form a spiral galaxy than an elliptical galaxy.

Accepted Answer

A) True 
 B)False

Question 12

Scale the Milky Way down to the size of a compact disc. Which of the following best describes the size, shape, and distance of the Andromeda Galaxy on the same scale?

Accepted Answer

A) a pecan nut about 1 centimeter away 
B) a grapefruit about 1 kilometer away 
C) a compact disk about the length of a football field away 
D) a grapefruit a few meters away 
E) a compact disk a few meters away

Question 13

The distinguishing feature of a starburst galaxy is _ .

Accepted Answer

A) a very large luminosity compared to the total luminosity of the Milky Way 
B) a rate of star formation that may be 100 or more times greater than that in the Milky Way 
C) strong radio emission from "lobes" of material well outside the visible boundaries of the galaxy 
D) the presence of an unusually large number of binary star systems containing X- ray bursters

Question 14

How was Edwin Hubble able to use his discovery of Cepheids in Andromeda to prove that the "spiral nebulae" were actually galaxies external to the Milky Way?

Accepted Answer

A) He measured the parallaxes of the Cepheids in Andromeda to determine their distances. He showed that Andromeda was far outside the Milky Way Galaxy. 
B) As a Cepheid is a type of luminous galaxy, Hubble's discovery of Cepheids in Andromeda proved that it was a separate galaxy from the Milky Way. 
C) From the period- luminosity relation for Cepheids, he was able to determine the distance to Andromeda. He showed that it was far outside the Milky Way Galaxy. 
D) There are no Cepheids in the Milky Way, so his discovery proved that Andromeda had to be in another galaxy. 
E) He used main- sequence fitting to determine the distances to the Cepheids. He showed that Andromeda was far outside the Milky Way Galaxy.

Question 15

Which of the following statements is not an assumption used in models of galaxy formation?

Accepted Answer

A) The universe started out filled almost uniformly with hydrogen and helium. 
B) Gas contracted to form the disks of galaxies before any stars were born. 
C) The universe is expanding. 
D) Some regions in the universe were slightly more dense than others.

Question 16

Why can't we see past the cosmological horizon?

Accepted Answer

A) Beyond the cosmological horizon, we would be looking back to a time before the universe was born. 
B) Every galaxy in the entire universe (not just the observable universe)exists within the cosmological horizon, so there's nothing to see beyond it. 
C) The cosmological horizon is infinitely far away, and we can't see to infinity. 
D) We do not have big enough telescopes.

Question 17

The mass of a supermassive black hole thought to power a typical bright active galactic nucleus is roughly .

Accepted Answer

A) 3 solar masses 
B) 1 billion solar masses 
C) 1 trillion solar masses 
D) 10 solar masses

Question 18

How does the age of the universe depend on the value of Hubble's constant, and why?

Accepted Answer

The answer of How does the age of the universe...

Question 19

According to current understanding, what is a quasar?

Accepted Answer

A) any object with an extremely large redshift 
B) an active galactic nucleus that is particularly bright 
C) a very large galaxy thought to be formed by the merger of several smaller galaxies, typically found in the center of a galaxy cluster 
D) a galaxy with an unusually high rate of star formation

Question 20

Cosmological redshift is the result of .

Accepted Answer

A) supermassive black holes 
B) the expansion of the universe 
C) very old, red stars in distant galaxies 
D) the high speeds at which galaxies move within clusters

Exam 16: A Universe of Galaxies