Question 1

Which of the following best describes why a white dwarf cannot have a mass greater than the 1.4-solar-mass limit?

Accepted Answer

A)  Electron degeneracy pressure depends on the speeds of electrons, which approach the speed of light as a white dwarf's mass approaches the 1.4-solar-mass limit. 
B)  White dwarfs get hotter with increasing mass, and above the 1.4-solar-mass limit they would be so hot that even their electrons would melt. 
C)  White dwarfs are made only from stars that have masses less than the 1.4-solar-mass limit. 
D)  The upper limit to a white dwarf's mass is something we have learned from observations, but no one knows why this limit exists. 
A)  Electron degeneracy pressure depends on the speeds of electrons, which approach the speed of light as a white dwarf's mass approaches the 1.4-solar-mass limit. 
B)  White dwarfs get hotter with increasing mass, and above the 1.4-solar-mass limit they would be so hot that even their electrons would melt. 
C)  White dwarfs are made only from stars that have masses less than the 1.4-solar-mass limit. 
D)  The upper limit to a white dwarf's mass is something we have learned from observations, but no one knows why this limit exists.

Question 2

Which of the following correctly describes how light will be affected as it tries to escape from a massive object?

Accepted Answer

A)  Light doesn't have mass; therefore, it is not affected by gravity. 
B)  Light escaping from a compact massive object, such as a neutron star, will be redshifted. 
C)  Light escaping from a compact massive object, such as a neutron star, will be blueshifted. 
D)  Visible light escaping from a compact massive object, such as a neutron star, will be redshifted, but higher frequencies, such as X-rays and gamma rays, will not be affected. 
E)  Less energetic light will not be able to escape from a compact massive object, such as a neutron star, but more energetic light will be able to. 
A)  Light doesn't have mass; therefore, it is not affected by gravity. 
B)  Light escaping from a compact massive object, such as a neutron star, will be redshifted. 
C)  Light escaping from a compact massive object, such as a neutron star, will be blueshifted. 
D)  Visible light escaping from a compact massive object, such as a neutron star, will be redshifted, but higher frequencies, such as X-rays and gamma rays, will not be affected. 
E)  Less energetic light will not be able to escape from a compact massive object, such as a neutron star, but more energetic light will be able to.

Question 3

Order these objects by size (radius) from smallest to largest:

Accepted Answer

A)  1 solar-mass white dwarf, 0.5 solar-mass white dwarf, a 3 solar-mass neutron star, a 3 solar-mass black hole. 
B)  3 solar mass neutron star, 3 solar mass black hole, 1 solar mass white dwarf, 0.5 solar mass white dwarf. 
C)  0.5 solar mass white dwarf, 1 solar mass white dwarf, a 3 solar mass neutron star, a 3 solar mass black hole. 
D)  3 solar mass black hole, 3 solar mass neutron star, 1 solar mass white dwarf, 0.5 solar mass white dwarf. 
E)  3 solar mass black hole, 3 solar mass neutron star, 0.5 solar mass white dwarf, 1 solar mass white dwarf. F) 0.5 solar mass white dwarf, 1 solar mass white dwarf, a 3 solar mass black hole, a 3 solar mass neutron star. 
A)  1 solar-mass white dwarf, 0.5 solar-mass white dwarf, a 3 solar-mass neutron star, a 3 solar-mass black hole. 
B)  3 solar mass neutron star, 3 solar mass black hole, 1 solar mass white dwarf, 0.5 solar mass white dwarf. 
C)  0.5 solar mass white dwarf, 1 solar mass white dwarf, a 3 solar mass neutron star, a 3 solar mass black hole. 
D)  3 solar mass black hole, 3 solar mass neutron star, 1 solar mass white dwarf, 0.5 solar mass white dwarf. 
E)  3 solar mass black hole, 3 solar mass neutron star, 0.5 solar mass white dwarf, 1 solar mass white dwarf. F) 0.5 solar mass white dwarf, 1 solar mass white dwarf, a 3 solar mass black hole, a 3 solar mass neutron star.

Question 4

The remnant left behind by a white-dwarf supernova is a neutron star.

Accepted Answer

A) True 
 B)False

Question 5

Imagine comparing a 1.2 solar mass white dwarf to a 1.0 solar mass white dwarf. Which of the following must be true?

Accepted Answer

A)  The 1.2 solar mass white dwarf has a larger radius. 
B)  The 1.2 solar mass white dwarf has a smaller radius. 
C)  The 1.2 solar mass white dwarf has a higher surface temperature. 
D)  The 1.2 solar mass white dwarf has a lower surface temperature. 
E)  The 1.2 solar mass white dwarf is supported by neutron degeneracy pressure; the 1 solar mass white dwarf is supported by electron degeneracy pressure. 
A)  The 1.2 solar mass white dwarf has a larger radius. 
B)  The 1.2 solar mass white dwarf has a smaller radius. 
C)  The 1.2 solar mass white dwarf has a higher surface temperature. 
D)  The 1.2 solar mass white dwarf has a lower surface temperature. 
E)  The 1.2 solar mass white dwarf is supported by neutron degeneracy pressure; the 1 solar mass white dwarf is supported by electron degeneracy pressure.

Question 6

A white dwarf is

Accepted Answer

A)  the exposed core of a dead star, supported by electron degeneracy pressure. 
B)  the exposed core of a dead star, supported by neutron degeneracy pressure. 
C)  a hot but very small main sequence star with a mass of less than 1.4 solar masses. 
D)  a cool and very small main sequence star with a mass of less than 1.4 of a solar masses. 
E)  the name for the singularity at the center of a black hole. 
A)  the exposed core of a dead star, supported by electron degeneracy pressure. 
B)  the exposed core of a dead star, supported by neutron degeneracy pressure. 
C)  a hot but very small main sequence star with a mass of less than 1.4 solar masses. 
D)  a cool and very small main sequence star with a mass of less than 1.4 of a solar masses. 
E)  the name for the singularity at the center of a black hole.

Question 7

You want to determine whether a mystery object is a neutron star or a white dwarf. Which of the following properties would demonstrate that it is definitely a neutron star?

Accepted Answer

A)  It dims and brightens more than twice per second. 
B)  It is surrounded by a planetary nebula. 
C)  It emits most strongly in visible and ultraviolet light. 
D)  Every decade or so, it erupts in a nova explosion. 
A)  It dims and brightens more than twice per second. 
B)  It is surrounded by a planetary nebula. 
C)  It emits most strongly in visible and ultraviolet light. 
D)  Every decade or so, it erupts in a nova explosion.

Question 8

What would happen if a small piece of neutron star material (say the size of a paper clip) struck the Earth?

Accepted Answer

The extremely dense material could not b

Question 9

How do we know that pulsars must be neutron stars?

Accepted Answer

A)  We have observed massive-star supernovae produce pulsars. 
B)  Telescopic images of pulsars and neutron stars look exactly the same. 
C)  No massive object, other than a neutron star, could spin as fast as we observe pulsars to spin and remain intact. 
D)  Pulsars have the same upper mass limit as neutron stars do. 
E)  This is only a theory that has not yet been confirmed by observations. 
A)  We have observed massive-star supernovae produce pulsars. 
B)  Telescopic images of pulsars and neutron stars look exactly the same. 
C)  No massive object, other than a neutron star, could spin as fast as we observe pulsars to spin and remain intact. 
D)  Pulsars have the same upper mass limit as neutron stars do. 
E)  This is only a theory that has not yet been confirmed by observations.

Question 10

Why does the size of a white dwarf decrease with increasing mass?

Accepted Answer

A more massive white dwarf has a stronge

Which of the following best describes why a white dwarf cannot have a mass greater than the 1.4-solar-mass limit?

Which of the following correctly describes how light will be affected as it tries to escape from a massive object?

Order these objects by size (radius) from smallest to largest:

The remnant left behind by a white-dwarf supernova is a neutron star.

Imagine comparing a 1.2 solar mass white dwarf to a 1.0 solar mass white dwarf. Which of the following must be true?

A white dwarf is

You want to determine whether a mystery object is a neutron star or a white dwarf. Which of the following properties would demonstrate that it is definitely a neutron star?

What would happen if a small piece of neutron star material (say the size of a paper clip) struck the Earth?

How do we know that pulsars must be neutron stars?

Why does the size of a white dwarf decrease with increasing mass?

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Asteroids, Comets, and Dwarf Planets: Their Nature, Orbits, and Impacts

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Exam 13: Bizarre Stellar Graveyard

Which of the following best describes why a white dwarf cannot have a mass greater than the 1.4-solar-mass limit?

Which of the following correctly describes how light will be affected as it tries to escape from a massive object?

Order these objects by size (radius) from smallest to largest:

The remnant left behind by a white-dwarf supernova is a neutron star.

Imagine comparing a 1.2 solar mass white dwarf to a 1.0 solar mass white dwarf. Which of the following must be true?

A white dwarf is

You want to determine whether a mystery object is a neutron star or a white dwarf. Which of the following properties would demonstrate that it is definitely a neutron star?

What would happen if a small piece of neutron star material (say the size of a paper clip) struck the Earth?

How do we know that pulsars must be neutron stars?

Why does the size of a white dwarf decrease with increasing mass?

Our Place in the Universe

Discovering the Universe for Yourself

The Science of Astronomy

Making Sense of the Universe: Understanding Motion, Energy, and Gravity

Light: the Cosmic Messenger

Formation of Planetary Systems: Our Solar System and Beyond

Earth and the Terrestrial Worlds

Jovian Planet Systems

Asteroids, Comets, and Dwarf Planets: Their Nature, Orbits, and Impacts

Our Star

Surveying the Stars

Star Stuff

Our Galaxy

Galaxies and the Foundation of Modern Cosmology

Dark Matter, Dark Energy, and the Fate of the Universe

The Beginning of Time

Life in the Universe

Filters