Question 1

Which statement concerning black hole masses and Schwarzschild radii is not true?

Accepted Answer

A) In a binary system with a black hole,the Schwarzschild radius depends on the distance from the black hole to the companion star. 
B) The more massive the black hole,the larger the Schwarzschild radius. 
C) Even an object as small as you could become a black hole if there were some way to compress you to a size smaller than your Schwarzschild radius. 
D) For black holes produced in massive star supernovae,Schwarzschild radii are typically a few to a few tens of kilometers. 
A) In a binary system with a black hole,the Schwarzschild radius depends on the distance from the black hole to the companion star. 
B) The more massive the black hole,the larger the Schwarzschild radius. 
C) Even an object as small as you could become a black hole if there were some way to compress you to a size smaller than your Schwarzschild radius. 
D) For black holes produced in massive star supernovae,Schwarzschild radii are typically a few to a few tens of kilometers.

Question 2

What is the upper limit to the mass of a white dwarf?

Accepted Answer

A) There is no upper limit. 
B) There is an upper limit,but we do not yet know what it is. 
C) 2 solar masses 
D) 1.4 solar masses 
E) 1 solar mass 
A) There is no upper limit. 
B) There is an upper limit,but we do not yet know what it is. 
C) 2 solar masses 
D) 1.4 solar masses 
E) 1 solar mass

Question 3

Binary black holes have much higher masses than their white dwarf and neutron star counterparts,which should lead to a much stronger emission of gravitational waves.What is the most reasonable explanation for why we have not yet observed gravitational waves from black-hole binaries?

Accepted Answer

A) Black hole binaries are very rare,and wave detection is difficult. 
B) The waves disappear into the black hole. 
C) The waves must be coming from very far away and haven't reached us yet. 
D) Our current theories must be wrong. 
A) Black hole binaries are very rare,and wave detection is difficult. 
B) The waves disappear into the black hole. 
C) The waves must be coming from very far away and haven't reached us yet. 
D) Our current theories must be wrong.

Question 4

When we see X-rays from an accretion disk in a binary system,we can't immediately tell whether the accretion disk surrounds a neutron star or a black hole.Suppose we then observe each of the following phenomena in this system.Which one would rule out the possibility of a black hole?

Accepted Answer

A) intense X-ray bursts 
B) spectral lines from the companion star that alternately shift to shorter and longer wavelengths 
C) visible and ultraviolet light from the companion star 
D) bright X-ray emission that varies on a time scale of a few hours 
A) intense X-ray bursts 
B) spectral lines from the companion star that alternately shift to shorter and longer wavelengths 
C) visible and ultraviolet light from the companion star 
D) bright X-ray emission that varies on a time scale of a few hours

Question 5

A typical white dwarf is

Accepted Answer

A) as large in diameter as the Sun but only about as massive as Earth. 
B) as massive as the Sun but only about as large in size as Earth. 
C) about the same size and mass as the Sun but much hotter. 
D) as massive as the Sun but only about as large in size as Jupiter. 
A) as large in diameter as the Sun but only about as massive as Earth. 
B) as massive as the Sun but only about as large in size as Earth. 
C) about the same size and mass as the Sun but much hotter. 
D) as massive as the Sun but only about as large in size as Jupiter.

Question 6

White dwarfs are so called because

Accepted Answer

A) they are both very hot and very small. 
B) they are the end-products of small,low-mass stars. 
C) they are the opposite of black holes. 
D) it amplifies the contrast with red giants. 
E) they are supported by electron degeneracy pressure. 
A) they are both very hot and very small. 
B) they are the end-products of small,low-mass stars. 
C) they are the opposite of black holes. 
D) it amplifies the contrast with red giants. 
E) they are supported by electron degeneracy pressure.

Question 7

Why do white-dwarf supernovae all have the same maximum luminosity?

Accepted Answer

White-dwarf supernovae occur when the ma

Question 8

Degeneracy pressure is the source of the pressure that stops the crush of gravity in all the following except

Accepted Answer

A) a brown dwarf. 
B) a white dwarf. 
C) a neutron star. 
D) a very massive main-sequence star. 
E) the central core of the Sun after hydrogen fusion ceases but before helium fusion begins. 
A) a brown dwarf. 
B) a white dwarf. 
C) a neutron star. 
D) a very massive main-sequence star. 
E) the central core of the Sun after hydrogen fusion ceases but before helium fusion begins.

Question 9

Which of the following statements about black holes is not true?

Accepted Answer

A) If you watch someone else fall into a black hole,you will never see him or her cross the event horizon.However,he or she will fade from view as the light he or she emits (or reflects)becomes more and more redshifted. 
B) If we watch a clock fall toward a black hole,we will see it tick slower and slower as it falls nearer to the black hole. 
C) A black hole is truly a hole in spacetime,through which we could leave the observable universe. 
D) If the Sun magically disappeared and was replaced by a black hole of the same mass,Earth would soon be sucked into the black hole. 
E) If you fell into a black hole,you would experience time to be running normally as you plunged rapidly across the event horizon. 
A) If you watch someone else fall into a black hole,you will never see him or her cross the event horizon.However,he or she will fade from view as the light he or she emits (or reflects)becomes more and more redshifted. 
B) If we watch a clock fall toward a black hole,we will see it tick slower and slower as it falls nearer to the black hole. 
C) A black hole is truly a hole in spacetime,through which we could leave the observable universe. 
D) If the Sun magically disappeared and was replaced by a black hole of the same mass,Earth would soon be sucked into the black hole. 
E) If you fell into a black hole,you would experience time to be running normally as you plunged rapidly across the event horizon.

Question 10

Our Sun will likely undergo a nova event in about 5 billion years.

Accepted Answer

A) True 
 B)False

Question 11

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

Accepted Answer

A massive white dwarf has a stronger gra

Question 12

How does an accretion disk around a neutron star differ from an accretion disk around a white dwarf?

Accepted Answer

A) The accretion disk around a neutron star is made mostly of helium while the accretion disk around a white dwarf is made mostly of hydrogen. 
B) The accretion disk around a neutron star is more likely to give birth to planets. 
C) The accretion disk around a neutron star is much hotter and emits higher-energy radiation. 
D) The accretion disk around a neutron star always contains much more mass. 
A) The accretion disk around a neutron star is made mostly of helium while the accretion disk around a white dwarf is made mostly of hydrogen. 
B) The accretion disk around a neutron star is more likely to give birth to planets. 
C) The accretion disk around a neutron star is much hotter and emits higher-energy radiation. 
D) The accretion disk around a neutron star always contains much more mass.

Question 13

Which of the following observatories is most likely to discover a black hole in a binary system?

Accepted Answer

A) the Hubble Space Telescope 
B) the Chandra X-Ray Observatory 
C) the SOFIA airborne infrared observatory 
D) the Arecibo Radio Observatory 
A) the Hubble Space Telescope 
B) the Chandra X-Ray Observatory 
C) the SOFIA airborne infrared observatory 
D) the Arecibo Radio Observatory

Question 14

Which of statement below about black holes is not true?

Accepted Answer

A) Although we are not 100% certain that black holes exist,we have strong observational evidence in favor of their existence. 
B) If you watch someone else fall into a black hole,you will never see him (or her)cross the event horizon;you'll only see him fade from view as the light he emits or reflects becomes more and more redshifted. 
C) A spaceship passing near a 10-solar-mass black hole is much more likely to be destroyed than a spaceship passing at the same distance from the center of a 10-solar-mass main-sequence star. 
D) If you fell into a black hole,you would experience time to be running normally as you plunged rapidly across the event horizon. 
A) Although we are not 100% certain that black holes exist,we have strong observational evidence in favor of their existence. 
B) If you watch someone else fall into a black hole,you will never see him (or her)cross the event horizon;you'll only see him fade from view as the light he emits or reflects becomes more and more redshifted. 
C) A spaceship passing near a 10-solar-mass black hole is much more likely to be destroyed than a spaceship passing at the same distance from the center of a 10-solar-mass main-sequence star. 
D) If you fell into a black hole,you would experience time to be running normally as you plunged rapidly across the event horizon.

Question 15

How does a 1.2-solar-mass white dwarf compare to a 1.0-solar-mass white dwarf?

Accepted Answer

A) It has a larger radius. 
B) It has a smaller radius. 
C) It has a higher surface temperature. 
D) It has a lower surface temperature. 
E) It is supported by neutron,rather than electron,degeneracy pressure. 
A) It has a larger radius. 
B) It has a smaller radius. 
C) It has a higher surface temperature. 
D) It has a lower surface temperature. 
E) It is supported by neutron,rather than electron,degeneracy pressure.

Question 16

What kind of pressure supports a white dwarf?

Accepted Answer

A) neutron degeneracy pressure 
B) electron degeneracy pressure 
C) thermal pressure 
D) radiation pressure 
E) all of the above 
A) neutron degeneracy pressure 
B) electron degeneracy pressure 
C) thermal pressure 
D) radiation pressure 
E) all of the above

Question 17

A teaspoonful of neutron star material on Earth would weigh

Accepted Answer

A) about the same as a teaspoonful of Earth-like material. 
B) a few tons. 
C) more than Mt.Everest. 
D) more than the Moon. 
E) more than Earth. 
A) about the same as a teaspoonful of Earth-like material. 
B) a few tons. 
C) more than Mt.Everest. 
D) more than the Moon. 
E) more than Earth.

Question 18

If you had something the size of a sugar cube that was made of white dwarf matter,it would weigh

Accepted Answer

A) as much as a truck. 
B) about 5 pounds. 
C) as much as the entire Earth. 
D) as much as an average person. 
A) as much as a truck. 
B) about 5 pounds. 
C) as much as the entire Earth. 
D) as much as an average person.

Question 19

Will our Sun ever undergo a white dwarf supernova explosion? Why or why not?

Accepted Answer

A) Yes,right at the end of its double-shell burning stage of life. 
B) Yes,about a million years after it becomes a white dwarf. 
C) No,because it is not orbited by another star. 
D) No,because the Sun's core will never be hot enough to fuse carbon and other heavier elements into iron. 
A) Yes,right at the end of its double-shell burning stage of life. 
B) Yes,about a million years after it becomes a white dwarf. 
C) No,because it is not orbited by another star. 
D) No,because the Sun's core will never be hot enough to fuse carbon and other heavier elements into iron.

Question 20

Why would Earth's orbit be unaffected were the Sun to suddenly become a black hole?

Accepted Answer

Earth's orbit (and those of the other pl

Exam 18: The Bizarre Stellar Graveyard

Which statement concerning black hole masses and Schwarzschild radii is not true?

What is the upper limit to the mass of a white dwarf?

Binary black holes have much higher masses than their white dwarf and neutron star counterparts,which should lead to a much stronger emission of gravitational waves.What is the most reasonable explanation for why we have not yet observed gravitational waves from black-hole binaries?

When we see X-rays from an accretion disk in a binary system,we can't immediately tell whether the accretion disk surrounds a neutron star or a black hole.Suppose we then observe each of the following phenomena in this system.Which one would rule out the possibility of a black hole?

A typical white dwarf is

White dwarfs are so called because

Why do white-dwarf supernovae all have the same maximum luminosity?

Degeneracy pressure is the source of the pressure that stops the crush of gravity in all the following except

Which of the following statements about black holes is not true?

Our Sun will likely undergo a nova event in about 5 billion years.

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

How does an accretion disk around a neutron star differ from an accretion disk around a white dwarf?

Which of the following observatories is most likely to discover a black hole in a binary system?

Which of statement below about black holes is not true?

How does a 1.2-solar-mass white dwarf compare to a 1.0-solar-mass white dwarf?

What kind of pressure supports a white dwarf?

A teaspoonful of neutron star material on Earth would weigh

If you had something the size of a sugar cube that was made of white dwarf matter,it would weigh

Will our Sun ever undergo a white dwarf supernova explosion? Why or why not?

Why would Earth's orbit be unaffected were the Sun to suddenly become a black hole?

A Modern View of the Universe

Discovering the Universe for Yourself

The Science of Astronomy

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

Light and Matter: Reading Messages from the Cosmos

Telescopes: Portals of Discovery

Our Planetary System

Formation of the Solar System

Planetary Geology: Earth and the Other Terrestrial Worlds

Planetary Atmospheres: Earth and the Other Terrestrial Worlds

Jovian Planet Systems

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

Other Planetary Systems: The New Science of Distant Worlds

Our Star

Surveying the Stars

Star Birth

Star Stuff

Our Galaxy

Galaxies and the Foundations of Modern Cosmology

Galaxy Evolution

The Birth of the Universe

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

Life in the Universe

Celestial Timekeeping and Navigation

Space and Time

Spacetime and Gravity

Building Blocks of the Universe

Filters