Question 1

How does the appearance of an AGN depend on the viewing angle to the nucleus?

Accepted Answer

An AGN of any type (e.g. ,Seyferts or qu

Question 2

We classify galaxies by:

Accepted Answer

A) their true shapes 
B) how they appear on the sky 
C) the amount of gas and dust in them 
D) whether they are near or far from us 
E) the amount of dark matter they contain 
A) their true shapes 
B) how they appear on the sky 
C) the amount of gas and dust in them 
D) whether they are near or far from us 
E) the amount of dark matter they contain

Question 3

Active star formation does not occur in elliptical galaxies because they:

Accepted Answer

A) rotate too fast 
B) contain little molecular hydrogen 
C) are too massive 
D) are too far away 
E) usually contain active nuclei 
A) rotate too fast 
B) contain little molecular hydrogen 
C) are too massive 
D) are too far away 
E) usually contain active nuclei

Question 4

Dark matter is distributed inside galaxies in exactly the same way as luminous matter,although the total mass of dark matter is much larger than that of luminous matter.

Accepted Answer

A) True 
 B)False

Question 5

Dark matter consists of material that emits radiation at wavelengths other than visible light.

Accepted Answer

A) True 
 B)False

Question 6

How did astronomers determine that elliptical galaxies are composed mostly of dark matter?

Accepted Answer

A) They measured the velocities of stars in the inner regions of the galaxies. 
B) They measured the rotation rates of gas as a function of distance from the centers of the galaxies. 
C) They measured the amount of gravitational pull elliptical galaxies have on companion galaxies. 
D) They assumed that the proportion of dark matter was roughly the same as in spiral galaxies. 
E) They measured X-ray emission from hot gas gravitationally bound to the galaxies. 
A) They measured the velocities of stars in the inner regions of the galaxies. 
B) They measured the rotation rates of gas as a function of distance from the centers of the galaxies. 
C) They measured the amount of gravitational pull elliptical galaxies have on companion galaxies. 
D) They assumed that the proportion of dark matter was roughly the same as in spiral galaxies. 
E) They measured X-ray emission from hot gas gravitationally bound to the galaxies.

Question 7

Which of these statements about quasars is FALSE?

Accepted Answer

A) Quasars are extremely luminous. 
B) Quasars are rare in our local vicinity. 
C) Quasars have high brightnesses. 
D) Quasars are extremely massive. 
E) Quasars are located at the centers of some active galaxies. 
A) Quasars are extremely luminous. 
B) Quasars are rare in our local vicinity. 
C) Quasars have high brightnesses. 
D) Quasars are extremely massive. 
E) Quasars are located at the centers of some active galaxies.

Question 8

The Hubble tuning fork diagram represents an evolutionary diagram of galaxies from elliptical to spiral.

Accepted Answer

A) True 
 B)False

Question 9

Long-lasting spiral density waves occur in the disk of a spiral galaxy when:

Accepted Answer

A) the spiral merges with another galaxy 
B) the galaxy is young 
C) the galaxy's disk is regularly disturbed 
D) the galaxy absorbs a satellite galaxy 
E) a supernova explosion takes place 
A) the spiral merges with another galaxy 
B) the galaxy is young 
C) the galaxy's disk is regularly disturbed 
D) the galaxy absorbs a satellite galaxy 
E) a supernova explosion takes place

Question 10

Why do rotation curves of galaxies imply that dark matter exists?

Accepted Answer

A) The velocity of stars rises dramatically at large distances from the centers of galaxies,implying large amounts of dark matter cause these stars to move much faster than stars at smaller distances. 
B) The velocity of stars stays approximately constant at distances well beyond the visible edges of galaxies,implying that galaxies contain much more matter than what we observe in stars and gas. 
C) The velocity of stars is low in the inner regions of galaxies,suggesting that dark matter is impeding their motion. 
D) The velocity of stars rises quickly in the inner regions of galaxies,suggesting that unseen matter is gravitationally moving this material at faster rates than expected. 
E) The velocity of stars falls slowly in the outer regions of galaxies,showing that while there is a lot of dark matter it is distributed the same way as is the visible light. 
A) The velocity of stars rises dramatically at large distances from the centers of galaxies,implying large amounts of dark matter cause these stars to move much faster than stars at smaller distances. 
B) The velocity of stars stays approximately constant at distances well beyond the visible edges of galaxies,implying that galaxies contain much more matter than what we observe in stars and gas. 
C) The velocity of stars is low in the inner regions of galaxies,suggesting that dark matter is impeding their motion. 
D) The velocity of stars rises quickly in the inner regions of galaxies,suggesting that unseen matter is gravitationally moving this material at faster rates than expected. 
E) The velocity of stars falls slowly in the outer regions of galaxies,showing that while there is a lot of dark matter it is distributed the same way as is the visible light.

Question 11

What makes up the majority of the mass of an individual spiral galaxy?

Accepted Answer

A) a central supermassive black hole 
B) dark matter 
C) massive O- and B-type stars 
D) cold molecular gas clouds 
E) low-mass G-,K-,and M-type stars 
A) a central supermassive black hole 
B) dark matter 
C) massive O- and B-type stars 
D) cold molecular gas clouds 
E) low-mass G-,K-,and M-type stars

Question 12

We know that spiral galaxies contain dark matter because the gas in the disk rotates with a velocity that decreases in a way that is proportional to r-1/2.

Accepted Answer

A) True 
 B)False

Question 13

Quasars were first discovered in which region of the electromagnetic spectrum?

Accepted Answer

A) X-ray 
B) gamma-ray 
C) radio 
D) infrared 
E) visible 
A) X-ray 
B) gamma-ray 
C) radio 
D) infrared 
E) visible

Question 14

What is the most likely candidate for making up the dark matter in galaxies?

Accepted Answer

The most likely source of the

Question 15

If you measure the spectrum emitted by a cloud of gas that orbits a nearby spiral galaxy and the observed wavelength of a hydrogen emission line is 658.4 nm while the rest wavelength of that line is 656.3 nm,what is the velocity of this gas cloud along your line of sight (i.e. ,the radial velocity)? Note that the speed of light is 3 × 105 km/s.

Accepted Answer

A) 960 km/s 
B) 1,200 km/s 
C) 2,300 km/s 
D) 3,800 km/s 
E) 4,400 km/s 
A) 960 km/s 
B) 1,200 km/s 
C) 2,300 km/s 
D) 3,800 km/s 
E) 4,400 km/s

Question 16

What type of galaxy is this?

Accepted Answer

A) a giant elliptical 
B) a regular spiral galaxy 
C) an irregular galaxy 
D) a barred spiral 
E) a dwarf elliptical 
A) a giant elliptical 
B) a regular spiral galaxy 
C) an irregular galaxy 
D) a barred spiral 
E) a dwarf elliptical

Question 17

If you measure the velocity of a cloud of gas that is rotating around the center of a galaxy in a circular orbit with radius R,you can determine:

Accepted Answer

A) the total mass of the galaxy 
B) the mass of the stars and gas in the galaxy 
C) the mass of the galaxy enclosed within the radius R 
D) the mass of the galaxy located outside the radius R 
E) the mass of luminous matter within the radius R 
A) the total mass of the galaxy 
B) the mass of the stars and gas in the galaxy 
C) the mass of the galaxy enclosed within the radius R 
D) the mass of the galaxy located outside the radius R 
E) the mass of luminous matter within the radius R

Question 18

Spiral structure can be triggered in a disk galaxy by:

Accepted Answer

A) the merger of close binary stars 
B) a supernova explosion 
C) the presence of an active nucleus 
D) the gravity of distant galaxies 
E) any disturbance to the disk 
A) the merger of close binary stars 
B) a supernova explosion 
C) the presence of an active nucleus 
D) the gravity of distant galaxies 
E) any disturbance to the disk

Question 19

Which of these would NOT be useful for measuring the mass of the dark matter halo in a spiral galaxy?

Accepted Answer

A) Hα emission from H II regions in the spiral disk 
B) the velocities of satellite dwarf galaxies surrounding a spiral galaxy 
C) absorption lines in the spectra of its globular clusters 
D) the velocities of star clusters in the outer disk 
E) all of these can be used to measure the mass of the dark matter 
A) Hα emission from H II regions in the spiral disk 
B) the velocities of satellite dwarf galaxies surrounding a spiral galaxy 
C) absorption lines in the spectra of its globular clusters 
D) the velocities of star clusters in the outer disk 
E) all of these can be used to measure the mass of the dark matter

Question 20

How did Hubble use his tuning fork diagram to classify galaxies? Is there any significance to this organization?

Accepted Answer

Elliptical and spiral galaxies are organ

Exam 20: Galaxies

How does the appearance of an AGN depend on the viewing angle to the nucleus?

We classify galaxies by:

Active star formation does not occur in elliptical galaxies because they:

Dark matter is distributed inside galaxies in exactly the same way as luminous matter,although the total mass of dark matter is much larger than that of luminous matter.

Dark matter consists of material that emits radiation at wavelengths other than visible light.

How did astronomers determine that elliptical galaxies are composed mostly of dark matter?

Which of these statements about quasars is FALSE?

The Hubble tuning fork diagram represents an evolutionary diagram of galaxies from elliptical to spiral.

Long-lasting spiral density waves occur in the disk of a spiral galaxy when:

Why do rotation curves of galaxies imply that dark matter exists?

What makes up the majority of the mass of an individual spiral galaxy?

We know that spiral galaxies contain dark matter because the gas in the disk rotates with a velocity that decreases in a way that is proportional to r-1/2.

Quasars were first discovered in which region of the electromagnetic spectrum?

What is the most likely candidate for making up the dark matter in galaxies?

What type of galaxy is this?

If you measure the velocity of a cloud of gas that is rotating around the center of a galaxy in a circular orbit with radius R,you can determine:

Spiral structure can be triggered in a disk galaxy by:

Which of these would NOT be useful for measuring the mass of the dark matter halo in a spiral galaxy?

How did Hubble use his tuning fork diagram to classify galaxies? Is there any significance to this organization?

Why Learn Astronomy

Patterns in the Skymotions of Earth

Motion of Astronomical Bodies

Gravity and Orbits

Light

The Tools of the Astronomer

The Birth and Evolution of Planetary Systems

The Terrestrial Planets and Earths Moon

Atmospheres of the Terrestrial Planets

Worlds of Gas and Liquid the Giant Planets

Planetary Adornments Moons and Rings

Dwarf Planets and Small Solar System Bodies

Taking the Measure of Stars

Our Starthe Sun

Star Formation and the Interstellar Medium

Evolution of Low-Mass Stars

Evolution of High-Mass Stars

Relativity and Black Holes

The Expanding Universe

The Milky Waya Normal Spiral Galaxy

Modern Cosmology

Large-Scale Structure in the Universe

Life

Filters

We know that spiral galaxies contain dark matter because the gas in the disk rotates with a velocity that decreases in a way that is proportional to r^-1/2.