Question 1

Which of the following would NOT be found in an elliptical galaxy?

Accepted Answer

A) novae 
B) Type I supernovae 
C) Type II supernovae 
D) planetary nebulae 
E) hot gas 
A) novae 
B) Type I supernovae 
C) Type II supernovae 
D) planetary nebulae 
E) hot gas C

Question 2

If the rotational speed of the gas in the disk of a spiral galaxy is 100 km/s at a distance of 26,000 light-years from its center,then what is the mass enclosed within this radius? If the mass of luminous matter inside this radius is 5 billion M⨀ then what fraction of the galaxy's mass is made of dark matter?

Accepted Answer

The radius of the gas is:
r = 26,000 ly = 26,000 × 9.5 × 10¹⁵ m = 2.5 × 10²⁰ m
and the mass enclosed within this radius is equal to
M = v² r/G = (10⁵ m/s)² × 2.5 × 10¹⁰ m/(6.7 × 10⁻¹¹ m³/kg s²) = 3.7 × 10⁴⁰ kg × (1M_⨀/2 × 10³⁰ kg).
M = 1.9 × 10¹⁰ M_⨀.
The fraction of mass in dark matter is (M − M_luminous)/M = (19 − 5)/19 = 0.74,and thus 74 percent of the mass inside this radius is made of dark matter.

Question 3

How do astronomers know that AGNs are as small as our Solar System?

Accepted Answer

AGNs have been observed to vary dramatically over less than a day.As AGNs give off light,any changes in emission will spread out over space depending on the size of the AGN.If variations are observed to vary over time scales of less than a day,then AGNs must be less than a light-day in size,which is about the size of our Solar System.

Question 4

Which of the following are NOT found mainly in the spiral arms of galaxies?

Accepted Answer

A) molecular clouds 
B) H II regions 
C) K- and M-type stars 
D) Type II supernovae 
E) O-type stars 
A) molecular clouds 
B) H II regions 
C) K- and M-type stars 
D) Type II supernovae 
E) O-type stars

Question 5

If the average quasar has a luminosity of 1014 L⨀ and an absolute magnitude of −30,and you discover one that has an apparent magnitude of +10,then what is its distance?

Accepted Answer

A) 10,000 Mpc 
B) 5,000 Mpc 
C) 1,000 Mpc 
D) 500 Mpc 
E) 0.1 Mpc 
A) 10,000 Mpc 
B) 5,000 Mpc 
C) 1,000 Mpc 
D) 500 Mpc 
E) 0.1 Mpc

Question 6

Star formation in spiral galaxies is enhanced in the spiral arms because more hot gas is concentrated there.

Accepted Answer

A) True 
 B)False

Question 7

What is the difference between a Seyfert galaxy and a normal spiral galaxy?

Accepted Answer

A Seyfert galaxy contains a lu

Question 8

The dark matter in galaxies is __________ the luminous material.

Accepted Answer

A) distributed in roughly the same way as 
B) much more extended in radius than 
C) much more centrally concentrated than 
D) much less uniform in density than 
E) much clumpier than 
A) distributed in roughly the same way as 
B) much more extended in radius than 
C) much more centrally concentrated than 
D) much less uniform in density than 
E) much clumpier than

Question 9

Astronomers have evidence that all giant galaxies probably contain supermassive black holes.

Accepted Answer

A) True 
 B)False

Question 10

Any asymmetry in the gravity field of a spiral galaxy can create spiral arms.

Accepted Answer

A) True 
 B)False

Question 11

We can determine the three-dimensional shape of any individual elliptical galaxy by photographing it.

Accepted Answer

A) True 
 B)False

Question 12

Roughly what percentage of the total mass of a galaxy is made up of luminous,or normal,matter?

Accepted Answer

A) 5 percent 
B) 25 percent 
C) 33 percent 
D) 50 percent 
E) 90 percent 
A) 5 percent 
B) 25 percent 
C) 33 percent 
D) 50 percent 
E) 90 percent

Question 13

What are the main components of an AGN?

Accepted Answer

All AGN of any luminosity cons

Question 14

Spiral structure:

Accepted Answer

A) rotates at the same speed as the gas in the disk 
B) rotates at a speed that is different than the gas in the disk 
C) stays constant in time as the gas in disk rotates through it 
D) rotates backward compared to the stellar orbits 
E) must only last a short time,since few galaxies with disks show spiral patterns 
A) rotates at the same speed as the gas in the disk 
B) rotates at a speed that is different than the gas in the disk 
C) stays constant in time as the gas in disk rotates through it 
D) rotates backward compared to the stellar orbits 
E) must only last a short time,since few galaxies with disks show spiral patterns

Question 15

The 3-D shape of an elliptical galaxy depends on the average velocity of its stars along each of the three axes.

Accepted Answer

A) True 
 B)False

Question 16

If you observed a gas cloud orbiting in a disk of a spiral galaxy that was located 10,000 pc from the center and it rotated with a speed of 300 km/s,what is the mass of the galaxy interior to gas cloud's orbit?

Accepted Answer

A) 1 × 1011 M⨀ 
B) 2 × 1011 M⨀ 
C) 8 × 1011 M⨀ 
D) 1 × 1012 M⨀ 
E) 4 × 1012 M⨀ 
A) 1 × 1011 M⨀ 
B) 2 × 1011 M⨀ 
C) 8 × 1011 M⨀ 
D) 1 × 1012 M⨀ 
E) 4 × 1012 M⨀

Question 17

Elliptical galaxies have the shapes they do because all the stars are orbiting in the same direction in the galaxy.

Accepted Answer

A) True 
 B)False

Question 18

The three-dimensional shape of __________ is set by the average velocities of the stars along each of the three axes.

Accepted Answer

A) spiral galaxies 
B) only elliptical galaxies 
C) spiral bulges 
D) elliptical galaxies and spiral bulges 
E) quasars 
A) spiral galaxies 
B) only elliptical galaxies 
C) spiral bulges 
D) elliptical galaxies and spiral bulges 
E) quasars

Question 19

If a Seyfert galaxy's nucleus varies in brightness on the timescale of 10 hours,then approximately what is the size of the emitting region?

Accepted Answer

A) 20 AU 
B) 30 AU 
C) 50 AU 
D) 70 AU 
E) 120 AU 
A) 20 AU 
B) 30 AU 
C) 50 AU 
D) 70 AU 
E) 120 AU

Question 20

Dark matter is most likely made up of:

Accepted Answer

A) elementary particles that have mass but do not interact much with normal matter 
B) supermassive black holes 
C) faint stellar remnants such as white dwarfs and neutron stars 
D) free-floating Jupiter-mass planets 
E) cold concentrations of dust 
A) elementary particles that have mass but do not interact much with normal matter 
B) supermassive black holes 
C) faint stellar remnants such as white dwarfs and neutron stars 
D) free-floating Jupiter-mass planets 
E) cold concentrations of dust

Exam 20: Galaxies

Which of the following would NOT be found in an elliptical galaxy?

How do astronomers know that AGNs are as small as our Solar System?

Which of the following are NOT found mainly in the spiral arms of galaxies?

If the average quasar has a luminosity of 1014 L⨀ and an absolute magnitude of −30,and you discover one that has an apparent magnitude of +10,then what is its distance?

Star formation in spiral galaxies is enhanced in the spiral arms because more hot gas is concentrated there.

What is the difference between a Seyfert galaxy and a normal spiral galaxy?

The dark matter in galaxies is __________ the luminous material.

Astronomers have evidence that all giant galaxies probably contain supermassive black holes.

Any asymmetry in the gravity field of a spiral galaxy can create spiral arms.

We can determine the three-dimensional shape of any individual elliptical galaxy by photographing it.

Roughly what percentage of the total mass of a galaxy is made up of luminous,or normal,matter?

What are the main components of an AGN?

Spiral structure:

The 3-D shape of an elliptical galaxy depends on the average velocity of its stars along each of the three axes.

If you observed a gas cloud orbiting in a disk of a spiral galaxy that was located 10,000 pc from the center and it rotated with a speed of 300 km/s,what is the mass of the galaxy interior to gas cloud's orbit?

Elliptical galaxies have the shapes they do because all the stars are orbiting in the same direction in the galaxy.

The three-dimensional shape of __________ is set by the average velocities of the stars along each of the three axes.

If a Seyfert galaxy's nucleus varies in brightness on the timescale of 10 hours,then approximately what is the size of the emitting region?

Dark matter is most likely made up of:

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

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If the average quasar has a luminosity of 10¹⁴ L_⨀ and an absolute magnitude of −30,and you discover one that has an apparent magnitude of +10,then what is its distance?