Question 1

Which star spends the longest time as a main-sequence star?

Accepted Answer

A)   
B)   
C)   
D)   E) None of the above
F) C) and D)

Question 2

What ionizes the gas in a planetary nebula and makes it visible?

Accepted Answer

A)   X-ray photons emitted by a pulsar
B)   Ultraviolet photons emitted by a white dwarf
C)   The shock wave from a supernova
D)   Hydrogen burning in the nebular gasE) None of the above
F) A) and B)

Question 3

Calculate the main-sequence lifetimes of the following stars of different spectral types:  ,  ,  ,  ,and  .What trend do you notice in your results?

Accepted Answer

Main-sequence liftetime:

...

Question 4

A low-mass star that burns helium in its core and hydrogen in a shell is more luminous than a similar star that burns only hydrogen in a shell around a dead core.

Accepted Answer

A) True 
 B)False

Question 5

A Type I supernova has a luminosity of approximately

Accepted Answer

A)    .
B)    .
C)    .
D)    .E) A) and B)
F) B) and C)

Question 6

Why does the core of a main-sequence star have to be hotter to burn helium into carbon than hydrogen into helium?

Accepted Answer

A helium nucleus has two protons and a net charge of +2,while the hydrogen nucleus has only one proton and a charge of +1.Because the electrostatic repulsion between a nucleus and proton is proportional to the charges of each,the helium nucleus will repulse a proton with two times more force than a hydrogen nucleus.Therefore the helium nuclei must be moving with a higher speed to overcome this repulsion and make the first step in the triple-alpha reactions.Thus,the core of the star must be hotter to burn helium.

Question 7

When a low-mass star becomes an AGB star and has a temperature of 3,300 K,at what wavelength will it shine the brightest?

Accepted Answer

A)   650 nm,red visible
B)   880 nm,infrared
C)   1 mm,microwave
D)   10 m,radioE) A) and C)
F) A) and D)

Question 8

During which phase of the evolution of a low-mass star does it have two separate regions of nuclear burning occurring in its interior?

Accepted Answer

A)   main sequence
B)   red giant
C)   horizontal branch
D)   white dwarfE) None of the above
F) A) and B)

Question 9

If a  white dwarf could accrete matter from a binary companion at a rate of  ,how long would it take before it exploded as a Type I supernova?

Accepted Answer

A)   600 thousand years
B)   20 million years
C)   200 milllion years
D)   600 million yearsE) All of the above
F) C) and D)

Question 10

In a white dwarf,what is the source of pressure that halts its contraction as it cools?

Accepted Answer

A)   Thermal pressure of the extremely hot gas
B)   Electrons packed so closely that they become incompressible
C)   Neutrons that resist being pressed further together
D)   Carbon nuclei that repulse each other strongly because they each contain six protonsE) A) and D)
F) A) and C) B

Question 11

The Sun eventually could become a nova.

Accepted Answer

A) True 
 B)False

Question 12

The luminosity of a star depends on

Accepted Answer

A)   its mass,its age,and its distance.
B)   its mass.
C)   its age.
D)   its mass and its age.E) A) and D)
F) A) and C)

Question 13

One star in a binary will almost always become a red giant before the other because

Accepted Answer

A)   one star is always larger than the other.
B)   binaries always have one star twice as massive as the other.
C)   small differences in main-sequence masses yield large differences in main-sequence ages.
D)   the more massive binary star always gets more mass from the less massive binary star when both are main-sequence stars.E) A) and D)
F) B) and C)

Question 14

Pressure from degenerate electrons keeps the core of a red giant star from collapsing.

Accepted Answer

A) True 
 B)False

Question 15

Why are novae thought to be recurrent?

Accepted Answer

The explosive hydrogen burning on the su...

Question 16

A star's surface temperature during the horizontal branch phase is determined primarily by its

Accepted Answer

A)   luminosity.
B)   chemical composition.
C)   magnetic field strength.
D)   rotation rate.E) B) and D)
F) All of the above

Question 17

How long will a  star live as a main-sequence star?

Accepted Answer

A)   12 million years
B)   1.8 billion years
C)   12 billion years
D)   180 million yearsE) None of the above
F) B) and D)

Question 18

The percent of hydrogen in the Sun's core today is roughly half of what it had originally.

Accepted Answer

A) True 
 B)False  True

Question 19

Stars evolve primarily because they run out of fuel in their cores.

Accepted Answer

A) True 
 B)False

Question 20

When the Sun becomes an AGB star,its radius will be approximately  .If its mass at this point will be approximately the same as it is now,how will its surface gravity as an AGB star compare to its present surface gravity as a main-sequence star? Note that  .

Accepted Answer

Surface gravity:

Thus,when t...

Exam 16: Stars in the Slow Lanelow-Mass Stellar Evolution

Which star spends the longest time as a main-sequence star?

Correct Answer
verified

What ionizes the gas in a planetary nebula and makes it visible?

Correct Answer
verified

Calculate the main-sequence lifetimes of the following stars of different spectral types: , , , ,and .What trend do you notice in your results?

Correct Answer
verified
Main-sequence liftetime: ...
View Answer

A low-mass star that burns helium in its core and hydrogen in a shell is more luminous than a similar star that burns only hydrogen in a shell around a dead core.

Correct Answer
verified

A Type I supernova has a luminosity of approximately

Correct Answer
verified

Why does the core of a main-sequence star have to be hotter to burn helium into carbon than hydrogen into helium?

When a low-mass star becomes an AGB star and has a temperature of 3,300 K,at what wavelength will it shine the brightest?

Correct Answer
verified

During which phase of the evolution of a low-mass star does it have two separate regions of nuclear burning occurring in its interior?

Correct Answer
verified

If a white dwarf could accrete matter from a binary companion at a rate of ,how long would it take before it exploded as a Type I supernova?

Correct Answer
verified

In a white dwarf,what is the source of pressure that halts its contraction as it cools?

Correct Answer
verified
B

The Sun eventually could become a nova.

Correct Answer
verified

The luminosity of a star depends on

Correct Answer
verified

One star in a binary will almost always become a red giant before the other because

Correct Answer
verified

Pressure from degenerate electrons keeps the core of a red giant star from collapsing.

Correct Answer
verified

Why are novae thought to be recurrent?

Correct Answer
verified
The explosive hydrogen burning on the su...
View Answer

A star's surface temperature during the horizontal branch phase is determined primarily by its

Correct Answer
verified

How long will a star live as a main-sequence star?

Correct Answer
verified

The percent of hydrogen in the Sun's core today is roughly half of what it had originally.

Correct Answer
verified
True

Stars evolve primarily because they run out of fuel in their cores.

Correct Answer
verified

When the Sun becomes an AGB star,its radius will be approximately .If its mass at this point will be approximately the same as it is now,how will its surface gravity as an AGB star compare to its present surface gravity as a main-sequence star? Note that .

Correct Answer
verified
Surface gravity: Thus,when t...
View Answer

Exam 16: Stars in the Slow Lanelow-Mass Stellar Evolution

Which star spends the longest time as a main-sequence star?

Correct AnswerverifiedShow Answer

What ionizes the gas in a planetary nebula and makes it visible?

Correct AnswerverifiedShow Answer

Calculate the main-sequence lifetimes of the following stars of different spectral types: , , , ,and .What trend do you notice in your results?

Correct AnswerverifiedMain-sequence liftetime: ...View AnswerShow Answer

A low-mass star that burns helium in its core and hydrogen in a shell is more luminous than a similar star that burns only hydrogen in a shell around a dead core.

Correct AnswerverifiedShow Answer

A Type I supernova has a luminosity of approximately

Correct AnswerverifiedShow Answer

Why does the core of a main-sequence star have to be hotter to burn helium into carbon than hydrogen into helium?

When a low-mass star becomes an AGB star and has a temperature of 3,300 K,at what wavelength will it shine the brightest?

Correct AnswerverifiedShow Answer

During which phase of the evolution of a low-mass star does it have two separate regions of nuclear burning occurring in its interior?

Correct AnswerverifiedShow Answer

If a white dwarf could accrete matter from a binary companion at a rate of ,how long would it take before it exploded as a Type I supernova?

Correct AnswerverifiedShow Answer

In a white dwarf,what is the source of pressure that halts its contraction as it cools?

Correct AnswerverifiedB

The Sun eventually could become a nova.

Correct AnswerverifiedShow Answer

The luminosity of a star depends on

Correct AnswerverifiedShow Answer

One star in a binary will almost always become a red giant before the other because

Correct AnswerverifiedShow Answer

Pressure from degenerate electrons keeps the core of a red giant star from collapsing.

Correct AnswerverifiedShow Answer

Why are novae thought to be recurrent?

Correct AnswerverifiedThe explosive hydrogen burning on the su...View AnswerShow Answer

A star's surface temperature during the horizontal branch phase is determined primarily by its

Correct AnswerverifiedShow Answer

How long will a star live as a main-sequence star?

Correct AnswerverifiedShow Answer

The percent of hydrogen in the Sun's core today is roughly half of what it had originally.

Correct AnswerverifiedTrue

Stars evolve primarily because they run out of fuel in their cores.

Correct AnswerverifiedShow Answer

When the Sun becomes an AGB star,its radius will be approximately .If its mass at this point will be approximately the same as it is now,how will its surface gravity as an AGB star compare to its present surface gravity as a main-sequence star? Note that .

Correct AnswerverifiedSurface gravity: Thus,when t...View AnswerShow Answer

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified
Main-sequence liftetime: ...
View Answer

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified
B

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified
The explosive hydrogen burning on the su...
View Answer

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified
True

Correct Answer
verified

Correct Answer
verified
Surface gravity: Thus,when t...
View Answer