Question 1

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 2

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 protons 
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 protons B

Question 3

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 4

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 years 
A)  600 thousand years 
B)  20 million years 
C)  200 milllion years 
D)  600 million years

Question 5

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 gas 
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 gas

Question 6

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. 
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.

Question 7

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

Accepted Answer

A) True 
 B)False

Question 8

A Type I supernova has a luminosity of approximately

Accepted Answer

A)    . 
B)    . 
C)    . 
D)    . 
A)    . 
B)    . 
C)    . 
D)    .

Question 9

The Sun eventually could become a nova.

Accepted Answer

A) True 
 B)False

Question 10

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. 
A)  luminosity. 
B)  chemical composition. 
C)  magnetic field strength. 
D)  rotation rate.

Question 11

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

Question 12

Why are novae thought to be recurrent?

Accepted Answer

The explosive hydrogen burning on the su

Question 13

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: @#IMG-DLM& @#IMG-DLM& Thus,when t

Question 14

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 dwarf 
A)  main sequence 
B)  red giant 
C)  horizontal branch 
D)  white dwarf

Question 15

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: @#IMG-DLM& @#IMG-DLM& @#IMG-DLM& @#IMG-DLM& @#IMG-DLM&

Question 16

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

Question 17

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

Accepted Answer

A)    
B)    
C)    
D)    
A)    
B)    
C)    
D)

Question 18

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 years 
A)  12 million years 
B)  1.8 billion years 
C)  12 billion years 
D)  180 million years

Question 19

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

Accepted Answer

A) True 
 B)False

Question 20

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

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

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

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

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

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?

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

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

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

A Type I supernova has a luminosity of approximately

The Sun eventually could become a nova.

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

The luminosity of a star depends on

Why are novae thought to be recurrent?

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 .

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

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

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?

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

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

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

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.

Why Learn Astronomy

Patterns in the Skymotions of Earth

Gravity and Orbitsa Celestial Ballet

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 Liquidthe Giant Planets

Gravity Is More Than Keplers Laws

Planetary Adornmentsmoons and Rings

Dwarf Planets and Small Solar System Bodies

Taking the Measure of Stars

A Run-Of-The-Mill G-Type Starour Sun

Star Formation and the Interstellar Medium

Live Fast,die Younghigh-Mass Stellar Evolution

Our Expanding Universe

Galaxies

The Milky Waya Normal Spiral Galaxy

Modern Cosmology

The Origin of Structure

Life

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