Question 1

How is an X-ray burst (in an X-ray binary system)similar to a nova?

Accepted Answer

A) Both involve explosions on the surface of stellar corpse. 
B) Both typically recur every few hours to every few days. 
C) Both are thought to involve fusion of hydrogen into helium. 
D) Both result in the complete destruction of their host stars. 
A) Both involve explosions on the surface of stellar corpse. 
B) Both typically recur every few hours to every few days. 
C) Both are thought to involve fusion of hydrogen into helium. 
D) Both result in the complete destruction of their host stars.

Question 2

What happens to two neutron stars that are orbiting so close together they emit gravitational waves?

Accepted Answer

A) The neutron stars will fly apart from one another. 
B) It has no effect. 
C) The neutron stars will spiral together and merge. 
D) The neutron stars will recombine and form a new,young star. 
A) The neutron stars will fly apart from one another. 
B) It has no effect. 
C) The neutron stars will spiral together and merge. 
D) The neutron stars will recombine and form a new,young star.

Question 3

Briefly describe what you would see if your friend plunged into a black hole.

Accepted Answer

As he approached the black hole,he would

Question 4

It is impossible to tell the difference between the two types of supernovae.

Accepted Answer

A) True 
 B)False

Question 5

Which statement about pulsars is not thought to be true?

Accepted Answer

A) All pulsars are neutron stars,but not all neutron stars are pulsars. 
B) Pulsars can form only in close binary systems. 
C) A pulsar must have a very strong magnetic field and rotate quite rapidly. 
D) Pulsars are kept from collapsing by neutron degeneracy pressure. 
A) All pulsars are neutron stars,but not all neutron stars are pulsars. 
B) Pulsars can form only in close binary systems. 
C) A pulsar must have a very strong magnetic field and rotate quite rapidly. 
D) Pulsars are kept from collapsing by neutron degeneracy pressure.

Question 6

What does Einstein's general theory of relativity tell us about two co-orbiting white dwarfs?

Accepted Answer

A) They will emit gravitational waves that carry energy and angular momentum away from the system,causing the white dwarfs to gradually spiral inward toward each other and eventually merge. 
B) They will emit gravitational waves that carry energy and angular momentum toward the system,causing the white dwarfs to gradually spiral away from one another and eventually fly far apart. 
C) They will emit gravitational waves that carry energy and angular momentum away from the system,causing the white dwarfs to quickly spiral away from one another. 
D) They will never interact with one another. 
A) They will emit gravitational waves that carry energy and angular momentum away from the system,causing the white dwarfs to gradually spiral inward toward each other and eventually merge. 
B) They will emit gravitational waves that carry energy and angular momentum toward the system,causing the white dwarfs to gradually spiral away from one another and eventually fly far apart. 
C) They will emit gravitational waves that carry energy and angular momentum away from the system,causing the white dwarfs to quickly spiral away from one another. 
D) They will never interact with one another.

Question 7

Which of the following is closest in size (radius)to a white dwarf?

Accepted Answer

A) Earth 
B) a small city 
C) a football stadium 
D) a basketball 
E) the Sun 
A) Earth 
B) a small city 
C) a football stadium 
D) a basketball 
E) the Sun

Question 8

What is an accretion disk?

Accepted Answer

A) any flattened disk in space,such as the disk of the Milky Way Galaxy 
B) a disk of hot gas swirling rapidly around a white dwarf,neutron star,or black hole 
C) a stream of gas flowing from one star to its binary companion star 
D) a disk of material found around every white dwarf in the Milky Way Galaxy 
A) any flattened disk in space,such as the disk of the Milky Way Galaxy 
B) a disk of hot gas swirling rapidly around a white dwarf,neutron star,or black hole 
C) a stream of gas flowing from one star to its binary companion star 
D) a disk of material found around every white dwarf in the Milky Way Galaxy

Question 9

What kind of star is most likely to become a white-dwarf supernova?

Accepted Answer

A) an O star 
B) a star like our Sun 
C) a binary M star 
D) a white dwarf star with a red giant binary companion 
E) a pulsar 
A) an O star 
B) a star like our Sun 
C) a binary M star 
D) a white dwarf star with a red giant binary companion 
E) a pulsar

Question 10

What is the ultimate fate of an isolated white dwarf?

Accepted Answer

A) It will cool down and become a cold black dwarf. 
B) As gravity overwhelms the electron degeneracy pressure,it will explode as a nova. 
C) As gravity overwhelms the electron degeneracy pressure,it will explode as a supernova. 
D) As gravity overwhelms the electron degeneracy pressure,it will become a neutron star. 
E) The electron degeneracy pressure will eventually overwhelm gravity and the white dwarf will slowly evaporate. 
A) It will cool down and become a cold black dwarf. 
B) As gravity overwhelms the electron degeneracy pressure,it will explode as a nova. 
C) As gravity overwhelms the electron degeneracy pressure,it will explode as a supernova. 
D) As gravity overwhelms the electron degeneracy pressure,it will become a neutron star. 
E) The electron degeneracy pressure will eventually overwhelm gravity and the white dwarf will slowly evaporate.

Question 11

Prior to the 1990s,most astronomers assumed that gamma-ray bursts came from neutron stars with accretion disks.How do we now know that this hypothesis was wrong?

Accepted Answer

A) We now know that gamma-ray bursts come not from neutron stars but from black holes. 
B) Theoretical work has proven that gamma rays cannot be produced in accretion disks. 
C) Observations from the Compton Gamma-Ray Observatory show that gamma-ray bursts come randomly from all directions in the sky. 
D) Observations from the Compton Gamma-Ray Observatory show that gamma-ray bursts occur too frequently to be attributed to neutron stars. 
E) Observations from the Compton Gamma-Ray Observatory have allowed us to trace gamma-ray bursts to pulsating variable stars in distant galaxies. 
A) We now know that gamma-ray bursts come not from neutron stars but from black holes. 
B) Theoretical work has proven that gamma rays cannot be produced in accretion disks. 
C) Observations from the Compton Gamma-Ray Observatory show that gamma-ray bursts come randomly from all directions in the sky. 
D) Observations from the Compton Gamma-Ray Observatory show that gamma-ray bursts occur too frequently to be attributed to neutron stars. 
E) Observations from the Compton Gamma-Ray Observatory have allowed us to trace gamma-ray bursts to pulsating variable stars in distant galaxies.

Question 12

How does the gravity of an object affect light?

Accepted Answer

A) Light doesn't have mass;therefore,it is not affected by gravity. 
B) Light coming from a compact massive object,such as a neutron star,will be redshifted. 
C) Light coming from a compact massive object,such as a neutron star,will be blueshifted. 
D) Visible light coming 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 coming from a compact massive object,such as a neutron star,will be redshifted. 
C) Light coming from a compact massive object,such as a neutron star,will be blueshifted. 
D) Visible light coming 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 13

Which of the following statements about novae is not true?

Accepted Answer

A) A star system that undergoes a nova may have another nova sometime in the future. 
B) A nova involves fusion taking place on the surface of a white dwarf. 
C) Our Sun will probably undergo at least one nova when it becomes a white dwarf about 5 billion years from now. 
D) When a star system undergoes a nova,it brightens considerably,but not as much as a star system undergoing a supernova. 
E) The word nova means "new star" and originally referred to stars that suddenly appeared in the sky,then disappeared again after a few weeks or months. 
A) A star system that undergoes a nova may have another nova sometime in the future. 
B) A nova involves fusion taking place on the surface of a white dwarf. 
C) Our Sun will probably undergo at least one nova when it becomes a white dwarf about 5 billion years from now. 
D) When a star system undergoes a nova,it brightens considerably,but not as much as a star system undergoing a supernova. 
E) The word nova means "new star" and originally referred to stars that suddenly appeared in the sky,then disappeared again after a few weeks or months.

Question 14

The white dwarf that remains when our Sun dies will be mostly made of

Accepted Answer

A) hydrogen. 
B) helium. 
C) carbon. 
D) neutrons. 
A) hydrogen. 
B) helium. 
C) carbon. 
D) neutrons.

Question 15

Which of the following statements about electron degeneracy pressure and neutron degeneracy pressure is true?

Accepted Answer

A) Electron degeneracy pressure is the main source of pressure in white dwarfs,while neutron degeneracy pressure is the main source of pressure in neutron stars. 
B) Both electron degeneracy pressure and neutron degeneracy pressure help govern the internal structure of a main-sequence star. 
C) The life of a white dwarf is an ongoing battle between electron degeneracy pressure and neutron degeneracy pressure. 
D) In a black hole,the pressure coming from neutron degeneracy pressure is slightly greater than that coming from electron degeneracy pressure. 
A) Electron degeneracy pressure is the main source of pressure in white dwarfs,while neutron degeneracy pressure is the main source of pressure in neutron stars. 
B) Both electron degeneracy pressure and neutron degeneracy pressure help govern the internal structure of a main-sequence star. 
C) The life of a white dwarf is an ongoing battle between electron degeneracy pressure and neutron degeneracy pressure. 
D) In a black hole,the pressure coming from neutron degeneracy pressure is slightly greater than that coming from electron degeneracy pressure.

Question 16

A neutron star is

Accepted Answer

A) the remains of a star that died by expelling its outer layers in a planetary nebula. 
B) a star made mostly of elements with high atomic mass numbers,so that they have lots of neutrons. 
C) the remains of a star that died in a massive star supernova (if no black hole was created). 
D) an object that will ultimately become a black hole. 
A) the remains of a star that died by expelling its outer layers in a planetary nebula. 
B) a star made mostly of elements with high atomic mass numbers,so that they have lots of neutrons. 
C) the remains of a star that died in a massive star supernova (if no black hole was created). 
D) an object that will ultimately become a black hole.

Question 17

Could our Sun ever undergo a nova or a white-dwarf supernova event? Why or why not?

Accepted Answer

No,because both events occur o

Question 18

The more massive a white dwarf,the

Accepted Answer

A) higher its temperature. 
B) smaller its radius. 
C) larger its radius. 
D) higher its luminosity. 
A) higher its temperature. 
B) smaller its radius. 
C) larger its radius. 
D) higher its luminosity.

Question 19

Which statement about accretion disks is not true?

Accepted Answer

A) The gas in the inner parts of the disk travels faster than the gas in the outer parts of the disk. 
B) The gas in the inner parts of the disk is hotter than the gas in the outer parts of the disk. 
C) The primary factor determining whether a white dwarf has an accretion disk is the white dwarf's mass. 
D) Accretion disks are made primarily of hydrogen and helium gas. 
A) The gas in the inner parts of the disk travels faster than the gas in the outer parts of the disk. 
B) The gas in the inner parts of the disk is hotter than the gas in the outer parts of the disk. 
C) The primary factor determining whether a white dwarf has an accretion disk is the white dwarf's mass. 
D) Accretion disks are made primarily of hydrogen and helium gas.

Question 20

All pulsars are neutron stars,but not all neutron stars are pulsars.

Accepted Answer

A) True 
 B)False

Exam 18: The Bizarre Stellar Graveyard

How is an X-ray burst (in an X-ray binary system)similar to a nova?

What happens to two neutron stars that are orbiting so close together they emit gravitational waves?

Briefly describe what you would see if your friend plunged into a black hole.

It is impossible to tell the difference between the two types of supernovae.

Which statement about pulsars is not thought to be true?

What does Einstein's general theory of relativity tell us about two co-orbiting white dwarfs?

Which of the following is closest in size (radius)to a white dwarf?

What is an accretion disk?

What kind of star is most likely to become a white-dwarf supernova?

What is the ultimate fate of an isolated white dwarf?

Prior to the 1990s,most astronomers assumed that gamma-ray bursts came from neutron stars with accretion disks.How do we now know that this hypothesis was wrong?

How does the gravity of an object affect light?

Which of the following statements about novae is not true?

The white dwarf that remains when our Sun dies will be mostly made of

Which of the following statements about electron degeneracy pressure and neutron degeneracy pressure is true?

A neutron star is

Could our Sun ever undergo a nova or a white-dwarf supernova event? Why or why not?

The more massive a white dwarf,the

Which statement about accretion disks is not true?

All pulsars are neutron stars,but not all neutron stars are pulsars.

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