Question 1

Why is the number of galaxies in the Local Group uncertain?

Accepted Answer

Answer not provided.

Question 2

What is the primary factor used in determining the classification for an elliptical galaxy?

Accepted Answer

A) size 
B) shape 
C) mass 
D) colour 
A) size 
B) shape 
C) mass 
D) colour B

Question 3

Describe the kind of observations that have led astronomers to believe that supermassive black holes lie at the centres of many galaxies.

Accepted Answer

Astronomers have made several observations that have led them to believe that supermassive black holes lie at the centers of many galaxies. One key observation is the high velocities of stars and gas near the centers of galaxies. These high velocities can only be explained by the presence of a massive object, such as a supermassive black hole, exerting a strong gravitational pull.

Another observation is the presence of intense radiation and energy emissions coming from the centers of galaxies, known as active galactic nuclei. These emissions are thought to be caused by the accretion of material onto supermassive black holes, which heats up and emits radiation as it falls into the black hole.

Additionally, astronomers have observed the effects of gravitational lensing, where the gravity of a supermassive black hole bends and distorts light from objects behind it, providing indirect evidence for the presence of these massive objects at the centers of galaxies.

Overall, these observations, along with others, have led astronomers to believe that supermassive black holes are indeed common at the centers of many galaxies.

Question 4

In the unified model of active galactic nuclei,what is the broad line region in an active galactic nucleus?

Accepted Answer

A) It is composed of clouds of gas and stars moving at very high orbital velocities near a supermassive black hole. 
B) It is composed of a super massive black hole surrounded by empty space. 
C) It is the region responsible for producing the bright continuous radiation from within the event horizon. 
D) It is the region responsible for the narrow absorption lines seen in Type 2 Seyfert galaxies. 
A) It is composed of clouds of gas and stars moving at very high orbital velocities near a supermassive black hole. 
B) It is composed of a super massive black hole surrounded by empty space. 
C) It is the region responsible for producing the bright continuous radiation from within the event horizon. 
D) It is the region responsible for the narrow absorption lines seen in Type 2 Seyfert galaxies.

Question 5

Which of the following describes part of the evolution of an elliptical galaxy?

Accepted Answer

A) It will turn into an irregular galaxy when it has used up all of its gas and dust. 
B) It may result from the collision and merger of spiral galaxies. 
C) It evolves from a single spiral galaxy when the spiral has used up all of its gas and dust. 
D) It would become a starburst galaxy if it were to move through the hot intergalactic medium of a cluster. 
A) It will turn into an irregular galaxy when it has used up all of its gas and dust. 
B) It may result from the collision and merger of spiral galaxies. 
C) It evolves from a single spiral galaxy when the spiral has used up all of its gas and dust. 
D) It would become a starburst galaxy if it were to move through the hot intergalactic medium of a cluster.

Question 6

What evidence leads astronomers to conclude that galaxies' shapes may be affected by the environment in which they are located?

Accepted Answer

A) the different rates of star formation in spiral and elliptical galaxies 
B) the different amounts of gas found in spiral and elliptical galaxies 
C) the large range of sizes of elliptical galaxies found in clusters 
D) the different fractions of galaxy types in rich clusters and poor clusters 
A) the different rates of star formation in spiral and elliptical galaxies 
B) the different amounts of gas found in spiral and elliptical galaxies 
C) the large range of sizes of elliptical galaxies found in clusters 
D) the different fractions of galaxy types in rich clusters and poor clusters

Question 7

How does the rotation curve method differ from the analysis of binary stars?

Accepted Answer

The answer of How does the rotation curve method differ...

Question 8

How does the unified model describe an active galactic nucleus?

Accepted Answer

A) as a supermassive black hole at the centre of a normal spiral galaxy 
B) as a supermassive black hole surrounded by an accretion disk and a dense disk of gas 
C) as an accretion disk around a neutron star 
D) as a gravitationally lensed high-redshift galaxy 
A) as a supermassive black hole at the centre of a normal spiral galaxy 
B) as a supermassive black hole surrounded by an accretion disk and a dense disk of gas 
C) as an accretion disk around a neutron star 
D) as a gravitationally lensed high-redshift galaxy

Question 9

Why are there few quasars at low redshifts and at high redshifts,but many at redshifts of about 2?

Accepted Answer

The answer of Why are there few quasars at low...

Question 10

Suppose you want to know the distance to a particular galaxy.What's the biggest problem with using type 1a supernovae to measure the distance?

Accepted Answer

A) Supernovae are extremely luminous and can outshine their galaxies. 
B) Supernovae all have about the same luminosity. 
C) Because supernovae are very energetic, they are not well understood. 
D) Supernovae are rare, so you might have to wait a long time. 
A) Supernovae are extremely luminous and can outshine their galaxies. 
B) Supernovae all have about the same luminosity. 
C) Because supernovae are very energetic, they are not well understood. 
D) Supernovae are rare, so you might have to wait a long time.

Question 11

When two galaxies collide,they pass through each other and their stars almost never collide.

Accepted Answer

A) True 
 B)False

Question 12

If the Hubble Space Telescope were used to take pictures of the entire sky,roughly how many galaxies would those pictures contain?

Accepted Answer

A) 1 million 
B) 10 million 
C) 1 billion 
D) 100 billion 
A) 1 million 
B) 10 million 
C) 1 billion 
D) 100 billion

Question 13

What observational evidence do we have that quasars are the centres of very distant galaxies?

Accepted Answer

Quasars, or quasi-stellar objects, are a

Question 14

When does gravitational lensing occur?

Accepted Answer

A) when light passes near a massive object and is deflected by the object's gravitational field 
B) when a galaxy has a central black hole with an accretion disk 
C) when the mass of a galaxy is greater than expected from the luminosity of the galaxy 
D) when the mass of a galaxy is less than expected from the luminosity of the galaxy 
A) when light passes near a massive object and is deflected by the object's gravitational field 
B) when a galaxy has a central black hole with an accretion disk 
C) when the mass of a galaxy is greater than expected from the luminosity of the galaxy 
D) when the mass of a galaxy is less than expected from the luminosity of the galaxy

Question 15

Centaurus A is a radio galaxy that has a visible galaxy at its centre.This central elliptical galaxy of Centaurus A is encircled by a ring of gas and dust,unlike most elliptical galaxies.The dust ring orbits about an axis that is perpendicular to the axis of rotation of the central elliptical galaxy.What does this suggest about this central elliptical galaxy of Centaurus A?

Accepted Answer

A) The radio jets have caused the dust disk to be driven around the elliptical galaxy. 
B) There are at least two black holes at the centre of the elliptical galaxy. 
C) Centaurus A is probably the result of a merger of an elliptical galaxy and a spiral galaxy. 
D) Dust is produced as the jets interact with the intergalactic medium. 
A) The radio jets have caused the dust disk to be driven around the elliptical galaxy. 
B) There are at least two black holes at the centre of the elliptical galaxy. 
C) Centaurus A is probably the result of a merger of an elliptical galaxy and a spiral galaxy. 
D) Dust is produced as the jets interact with the intergalactic medium.

Question 16

Why were quasars so mysterious when first discovered?

Accepted Answer

A) Quasars emitted radio energy like radio galaxies, but looked like stars in visible light. 
B) Quasars showed significant gravitational lens effects. 
C) The spectra of quasars looked like those of M dwarfs. 
D) The large redshifts originally indicated that they were orbiting the centre of the Milky Way. 
A) Quasars emitted radio energy like radio galaxies, but looked like stars in visible light. 
B) Quasars showed significant gravitational lens effects. 
C) The spectra of quasars looked like those of M dwarfs. 
D) The large redshifts originally indicated that they were orbiting the centre of the Milky Way.

Question 17

Our galaxy is not a radio galaxy,but it does emit radio energy.Explain where this radio energy comes from.

Accepted Answer

The radio energy emitted by our galaxy c

Question 18

What is the most important difference between an active galactic nucleus and a dormant black hole at the centre of a galaxy?

Accepted Answer

A) Active galactic nuclei are only found in elliptical galaxies, but dormant black holes are found in all galaxy types. 
B) The black holes in active galactic nuclei have much larger masses than those of dormant black holes. 
C) The black holes in active galactic nuclei have much smaller masses than those of dormant black holes. 
D) The black holes in active galactic nuclei have much more matter flowing into them. 
A) Active galactic nuclei are only found in elliptical galaxies, but dormant black holes are found in all galaxy types. 
B) The black holes in active galactic nuclei have much larger masses than those of dormant black holes. 
C) The black holes in active galactic nuclei have much smaller masses than those of dormant black holes. 
D) The black holes in active galactic nuclei have much more matter flowing into them.

Question 19

Which of the following types of objects is the Milky Way part of?

Accepted Answer

A) a rich cluster 
B) a poor cluster 
C) the Virgo cluster 
D) a globular cluster 
A) a rich cluster 
B) a poor cluster 
C) the Virgo cluster 
D) a globular cluster

Question 20

Some quasars have fuzz around them that produces spectra similar to those of normal galaxies.

Accepted Answer

A) True 
 B)False

Why is the number of galaxies in the Local Group uncertain?

What is the primary factor used in determining the classification for an elliptical galaxy?

Describe the kind of observations that have led astronomers to believe that supermassive black holes lie at the centres of many galaxies.

In the unified model of active galactic nuclei,what is the broad line region in an active galactic nucleus?

Which of the following describes part of the evolution of an elliptical galaxy?

What evidence leads astronomers to conclude that galaxies' shapes may be affected by the environment in which they are located?

How does the rotation curve method differ from the analysis of binary stars?

How does the unified model describe an active galactic nucleus?

Why are there few quasars at low redshifts and at high redshifts,but many at redshifts of about 2?

Suppose you want to know the distance to a particular galaxy.What's the biggest problem with using type 1a supernovae to measure the distance?

When two galaxies collide,they pass through each other and their stars almost never collide.

If the Hubble Space Telescope were used to take pictures of the entire sky,roughly how many galaxies would those pictures contain?

What observational evidence do we have that quasars are the centres of very distant galaxies?

When does gravitational lensing occur?

Why were quasars so mysterious when first discovered?

Our galaxy is not a radio galaxy,but it does emit radio energy.Explain where this radio energy comes from.

What is the most important difference between an active galactic nucleus and a dormant black hole at the centre of a galaxy?

Which of the following types of objects is the Milky Way part of?

Some quasars have fuzz around them that produces spectra similar to those of normal galaxies.

The Scale of the Cosmos

User's Guide to the Sky

The Origin of Modern Astronomy

Astronomical Telescopes and Instruments

Sun Light and Sun Atoms

The Family of Stars

The Structure and Formation of Stars

The Deaths of Stars

The Milky Way Galaxy

Cosmology in the 21st Century

The Origin of the Solar System

Comparative Planetology of the Terrestrial Planets

Comparative Planetology of the Jovian Planets

Life on Other Worlds

Filters

Exam 10: Galaxies

Why is the number of galaxies in the Local Group uncertain?

What is the primary factor used in determining the classification for an elliptical galaxy?

Describe the kind of observations that have led astronomers to believe that supermassive black holes lie at the centres of many galaxies.

In the unified model of active galactic nuclei,what is the broad line region in an active galactic nucleus?

Which of the following describes part of the evolution of an elliptical galaxy?

What evidence leads astronomers to conclude that galaxies' shapes may be affected by the environment in which they are located?

How does the rotation curve method differ from the analysis of binary stars?

How does the unified model describe an active galactic nucleus?

Why are there few quasars at low redshifts and at high redshifts,but many at redshifts of about 2?

Suppose you want to know the distance to a particular galaxy.What's the biggest problem with using type 1a supernovae to measure the distance?

When two galaxies collide,they pass through each other and their stars almost never collide.

If the Hubble Space Telescope were used to take pictures of the entire sky,roughly how many galaxies would those pictures contain?

What observational evidence do we have that quasars are the centres of very distant galaxies?

When does gravitational lensing occur?

Why were quasars so mysterious when first discovered?

Our galaxy is not a radio galaxy,but it does emit radio energy.Explain where this radio energy comes from.

What is the most important difference between an active galactic nucleus and a dormant black hole at the centre of a galaxy?

Which of the following types of objects is the Milky Way part of?

Some quasars have fuzz around them that produces spectra similar to those of normal galaxies.

The Scale of the Cosmos

User's Guide to the Sky

The Origin of Modern Astronomy

Astronomical Telescopes and Instruments

Sun Light and Sun Atoms

The Family of Stars

The Structure and Formation of Stars

The Deaths of Stars

The Milky Way Galaxy

Cosmology in the 21st Century

The Origin of the Solar System

Comparative Planetology of the Terrestrial Planets

Comparative Planetology of the Jovian Planets

Life on Other Worlds

Filters