Question 1

Which galaxy, as observed, has aged the most since it was born?

Accepted Answer

A) a nearby galaxy 
B) a very distant galaxy 
C) The distance of a galaxy doesn't matter. 
A) a nearby galaxy 
B) a very distant galaxy 
C) The distance of a galaxy doesn't matter.

Question 2

Galaxy collisions were more common in the past.

Accepted Answer

A) True 
 B)False

Question 3

Why is the Hyades Cluster important for building up a catalog of the true luminosities of main- sequence stars?

Accepted Answer

A) It is an extremely bright star cluster. 
B) It is an old globular cluster whose age we can determine very accurately by measuring its main- sequence turn- off point. 
C) It contains many Cepheid variable stars that can be used to determine its distance. 
D) It is close enough to us that the distance to its stars can be found by stellar parallax. 
E) It's a cluster that has been photographed over many decades, so we know how the stars vary in brightness. 
A) It is an extremely bright star cluster. 
B) It is an old globular cluster whose age we can determine very accurately by measuring its main- sequence turn- off point. 
C) It contains many Cepheid variable stars that can be used to determine its distance. 
D) It is close enough to us that the distance to its stars can be found by stellar parallax. 
E) It's a cluster that has been photographed over many decades, so we know how the stars vary in brightness.

Question 4

This figure shows the Cepheid period- luminosity relation. What is the approximate luminosity of a Cepheid star that varies in brightness on a 10 day cycle?

Accepted Answer

A) about 1000 times the luminosity of the sun 
B) about 30,000 times the luminosity of the sun 
C) about 10,000 times the luminosity of the sun 
D) about 3000 times the luminosity of the sun 
A) about 1000 times the luminosity of the sun 
B) about 30,000 times the luminosity of the sun 
C) about 10,000 times the luminosity of the sun 
D) about 3000 times the luminosity of the sun

Question 5

What is the most accurate way to determine the distance to a nearby galaxy?

Accepted Answer

A) radar ranging 
B) Cepheid variables 
C) main sequence fitting 
D) stellar parallax 
E) Hubble's law 
A) radar ranging 
B) Cepheid variables 
C) main sequence fitting 
D) stellar parallax 
E) Hubble's law

Question 6

Suppose we observe a source of X- rays that varies substantially in brightness over a period of a few days. What can we conclude?

Accepted Answer

A) The X- ray source must have a strong, rapidly varying magnetic field. 
B) We must be seeing the rapid orbit of two stars in a binary system. 
C) The X- ray source must be a quasar. 
D) The X- ray source must contain a black hole with an accretion disk. 
E) The X- ray source can be no more than a few light- days in diameter. 
A) The X- ray source must have a strong, rapidly varying magnetic field. 
B) We must be seeing the rapid orbit of two stars in a binary system. 
C) The X- ray source must be a quasar. 
D) The X- ray source must contain a black hole with an accretion disk. 
E) The X- ray source can be no more than a few light- days in diameter.

Question 7

Explain how we can estimate that there are about 50- 100 billion galaxies in the observable universe.

Accepted Answer

While it's impossible to count so many g

Question 8

What is a standard candle?

Accepted Answer

A) an object for which we can easily measure its apparent brightness 
B) an object for which we are likely to know its true luminosity 
C) any star for which we know its exact apparent brightness 
D) a class of objects that we know all have exactly the same luminosity 
E) a unit of luminosity used by astronomers 
A) an object for which we can easily measure its apparent brightness 
B) an object for which we are likely to know its true luminosity 
C) any star for which we know its exact apparent brightness 
D) a class of objects that we know all have exactly the same luminosity 
E) a unit of luminosity used by astronomers

Question 9

Based on counting the number of galaxies in a small patch of the sky and multiplying by the number of such patches needed to cover the entire sky, the total number of galaxies in the observable universe is estimated to be approximately

Accepted Answer

A) 100 billion. 
B) 10 billion. 
C) 100 million. 
D) 1 trillion. 
E) 1 billion. 
A) 100 billion. 
B) 10 billion. 
C) 100 million. 
D) 1 trillion. 
E) 1 billion.

Question 10

What is a quasar?

Accepted Answer

A) a star- like object that actually represents a bright patch of gas in the Milky Way 
B) the name given to the largest objects in the Kuiper Belt 
C) a very large galaxy thought to be formed by the merger of several smaller galaxies, resulting in a quick burst of star formation 
D) another name for very bright stars of spectral type O 
E) the extremely bright center of a distant galaxy, thought to be powered by a supermassive black hole 
A) a star- like object that actually represents a bright patch of gas in the Milky Way 
B) the name given to the largest objects in the Kuiper Belt 
C) a very large galaxy thought to be formed by the merger of several smaller galaxies, resulting in a quick burst of star formation 
D) another name for very bright stars of spectral type O 
E) the extremely bright center of a distant galaxy, thought to be powered by a supermassive black hole

Question 11

Compared to spiral galaxies, elliptical galaxies are

Accepted Answer

A) bluer and flattened. 
B) redder and rounder. 
C) always much smaller. 
D) redder and flattened. 
E) bluer and rounder. 
A) bluer and flattened. 
B) redder and rounder. 
C) always much smaller. 
D) redder and flattened. 
E) bluer and rounder.

Question 12

How do observations of galaxies at different distances help us learn about galaxy evolution?

Accepted Answer

A) We can observe the evolution of a single galaxy over time. 
B) We can observe galaxies at different distances merge, helping us learn how mergers affect evolution. 
C) Observations of the most distant galaxies will allow us to observe the birth of galaxies. 
D) Observations of different distances show galaxies of different ages and therefore different stages of evolution. 
E) We can see what our galaxy used to look like over time, helping us theorize about the physical processes that led to its current appearance. 
A) We can observe the evolution of a single galaxy over time. 
B) We can observe galaxies at different distances merge, helping us learn how mergers affect evolution. 
C) Observations of the most distant galaxies will allow us to observe the birth of galaxies. 
D) Observations of different distances show galaxies of different ages and therefore different stages of evolution. 
E) We can see what our galaxy used to look like over time, helping us theorize about the physical processes that led to its current appearance.

Question 13

The collision of two spiral galaxies will likely result in a single giant spiral galaxy.

Accepted Answer

A) True 
 B)False

Question 14

Which of the following phenomena is probably not related to the presence of a supermassive black hole?

Accepted Answer

A) the presence of globular clusters in the halos of galaxies 
B) the radio emission from radio galaxies 
C) the huge jets seen emerging from the centers of some galaxies 
D) quasars 
A) the presence of globular clusters in the halos of galaxies 
B) the radio emission from radio galaxies 
C) the huge jets seen emerging from the centers of some galaxies 
D) quasars

Question 15

Explain individual galaxies or clusters of galaxies do not expand in size despite the overall expansion of the universe implied by Hubble's Law.

Accepted Answer

The pull of gravity works to slow the ex

Question 16

In 1924, Edwin Hubble proved that the Andromeda Galaxy lay far beyond the bounds of the Milky Way, thus putting to rest the idea that it might have been a cloud within our own galaxy. How was he able to prove this?

Accepted Answer

A) He was the first person ever to look through a telescope at the object we now call the Andromeda Galaxy. 
B) By observing individual Cepheid variable stars in Andromeda and applying the period- luminosity relation 
C) He was able to measure the parallax of the Andromeda Galaxy. 
D) He found that the universe is expanding, and therefore concluded that Andromeda must lie outside our own galaxy. 
A) He was the first person ever to look through a telescope at the object we now call the Andromeda Galaxy. 
B) By observing individual Cepheid variable stars in Andromeda and applying the period- luminosity relation 
C) He was able to measure the parallax of the Andromeda Galaxy. 
D) He found that the universe is expanding, and therefore concluded that Andromeda must lie outside our own galaxy.

Question 17

Why should galaxy collisions have been more common in the past than they are today?

Accepted Answer

A) Galaxies were more active in the past and therefore would have collided with each other more frequently. 
B) Galaxies attracted each other more strongly in the past because they were more massive; they had not yet turned most of their mass into stars. 
C) Galaxies were much bigger in the past since they had not contracted completely. 
D) Galaxies were closer together in the past because the universe was smaller. 
A) Galaxies were more active in the past and therefore would have collided with each other more frequently. 
B) Galaxies attracted each other more strongly in the past because they were more massive; they had not yet turned most of their mass into stars. 
C) Galaxies were much bigger in the past since they had not contracted completely. 
D) Galaxies were closer together in the past because the universe was smaller.

Question 18

Approximately how many stars does a dwarf elliptical galaxy have?

Accepted Answer

A) less than a million 
B) 1 trillion 
C) 100 billion 
D) less than a billion 
E) 10 billion 
A) less than a million 
B) 1 trillion 
C) 100 billion 
D) less than a billion 
E) 10 billion

Question 19

How do astronomers use the Hubble Constant (H0)to estimate the age of the universe?

Accepted Answer

A) The age of the universe is about 600 million times H0. 
B) The inverse of H0 is the approximate age of the universe. 
C) They do not. The age of the universe is unknowable. 
A) The age of the universe is about 600 million times H0. 
B) The inverse of H0 is the approximate age of the universe. 
C) They do not. The age of the universe is unknowable.

Question 20

What evidence tells us that quasars are the centers of distant galaxies?

Accepted Answer

A) Images and spectra show quasars to be embedded at the centers of distant galaxies. 
B) Rapid variations in quasar luminosity tell us that they must be quite small in size. 
C) All quasars have large redshifts. 
D) Quasars are extremely luminous. 
A) Images and spectra show quasars to be embedded at the centers of distant galaxies. 
B) Rapid variations in quasar luminosity tell us that they must be quite small in size. 
C) All quasars have large redshifts. 
D) Quasars are extremely luminous.

Which galaxy, as observed, has aged the most since it was born?

Galaxy collisions were more common in the past.

Why is the Hyades Cluster important for building up a catalog of the true luminosities of main- sequence stars?

This figure shows the Cepheid period- luminosity relation. What is the approximate luminosity of a Cepheid star that varies in brightness on a 10 day cycle?

What is the most accurate way to determine the distance to a nearby galaxy?

Suppose we observe a source of X- rays that varies substantially in brightness over a period of a few days. What can we conclude?

Explain how we can estimate that there are about 50- 100 billion galaxies in the observable universe.

What is a standard candle?

Based on counting the number of galaxies in a small patch of the sky and multiplying by the number of such patches needed to cover the entire sky, the total number of galaxies in the observable universe is estimated to be approximately

What is a quasar?

Compared to spiral galaxies, elliptical galaxies are

How do observations of galaxies at different distances help us learn about galaxy evolution?

The collision of two spiral galaxies will likely result in a single giant spiral galaxy.

Which of the following phenomena is probably not related to the presence of a supermassive black hole?

Explain individual galaxies or clusters of galaxies do not expand in size despite the overall expansion of the universe implied by Hubble's Law.

In 1924, Edwin Hubble proved that the Andromeda Galaxy lay far beyond the bounds of the Milky Way, thus putting to rest the idea that it might have been a cloud within our own galaxy. How was he able to prove this?

Why should galaxy collisions have been more common in the past than they are today?

Approximately how many stars does a dwarf elliptical galaxy have?

How do astronomers use the Hubble Constant (H0)to estimate the age of the universe?

What evidence tells us that quasars are the centers of distant galaxies?

A Modern View of the Universe

Discovering the Universe for Yourself

The Science of Astronomy

Making Sense of the Universe: Understanding Motion, Energy, and Gravity

Light: the Cosmic Messenger

Formation of the Solar System

Earth and the Terrestrial Worlds

Jovian Planet System

Asteroids, Comets, and Dwarf Planets: Their Nature, Orbits, and Impacts

Other Planetary Systems: the New Science of Distant Worlds

Our Star

Surveying the Stars

Star Stuff

The Bizarre Stellar Graveyard

Our Galaxy

The Birth of the Universe

Dark Matter, Dark Energy, and the Fate of the Universe

Life in the Universe

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Exam 16: A Universe of Galaxies

Which galaxy, as observed, has aged the most since it was born?

Galaxy collisions were more common in the past.

Why is the Hyades Cluster important for building up a catalog of the true luminosities of main- sequence stars?

This figure shows the Cepheid period- luminosity relation. What is the approximate luminosity of a Cepheid star that varies in brightness on a 10 day cycle?

What is the most accurate way to determine the distance to a nearby galaxy?

Suppose we observe a source of X- rays that varies substantially in brightness over a period of a few days. What can we conclude?

Explain how we can estimate that there are about 50- 100 billion galaxies in the observable universe.

What is a standard candle?

Based on counting the number of galaxies in a small patch of the sky and multiplying by the number of such patches needed to cover the entire sky, the total number of galaxies in the observable universe is estimated to be approximately

What is a quasar?

Compared to spiral galaxies, elliptical galaxies are

How do observations of galaxies at different distances help us learn about galaxy evolution?

The collision of two spiral galaxies will likely result in a single giant spiral galaxy.

Which of the following phenomena is probably not related to the presence of a supermassive black hole?

Explain individual galaxies or clusters of galaxies do not expand in size despite the overall expansion of the universe implied by Hubble's Law.

In 1924, Edwin Hubble proved that the Andromeda Galaxy lay far beyond the bounds of the Milky Way, thus putting to rest the idea that it might have been a cloud within our own galaxy. How was he able to prove this?

Why should galaxy collisions have been more common in the past than they are today?

Approximately how many stars does a dwarf elliptical galaxy have?

How do astronomers use the Hubble Constant (H0)to estimate the age of the universe?

What evidence tells us that quasars are the centers of distant galaxies?

A Modern View of the Universe

Discovering the Universe for Yourself

The Science of Astronomy

Making Sense of the Universe: Understanding Motion, Energy, and Gravity

Light: the Cosmic Messenger

Formation of the Solar System

Earth and the Terrestrial Worlds

Jovian Planet System

Asteroids, Comets, and Dwarf Planets: Their Nature, Orbits, and Impacts

Other Planetary Systems: the New Science of Distant Worlds

Our Star

Surveying the Stars

Star Stuff

The Bizarre Stellar Graveyard

Our Galaxy

The Birth of the Universe

Dark Matter, Dark Energy, and the Fate of the Universe

Life in the Universe

Filters