Question 1

What causes X- ray bursters?

Accepted Answer

A) The binary companion of a neutron star spirals in and combines with the neutron star. 
B) The rapid rotation of the neutron star causes it to fly apart. 
C) Helium fusion, which occurs when the thin layer of accreted material on a neutron star reaches 100 million K 
D) The mass of an accreting neutron star passes a critical threshold between 2 and 3 Msun and explodes. 
A) The binary companion of a neutron star spirals in and combines with the neutron star. 
B) The rapid rotation of the neutron star causes it to fly apart. 
C) Helium fusion, which occurs when the thin layer of accreted material on a neutron star reaches 100 million K 
D) The mass of an accreting neutron star passes a critical threshold between 2 and 3 Msun and explodes.

Question 2

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

Accepted Answer

A) If we watch a clock fall toward a black hole, we will see it tick slower and slower as it falls towards the black hole. 
B) If you fell into a supermassive black hole (so that you could survive the tidal forces), you would experience time to be running normally as you plunged across the event horizon. 
C) If the Sun magically disappeared and was replaced by a black hole of the same mass, the Earth would soon be sucked into the black hole. 
D) 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 becomes more and more redshifted. 
E) The event horizon of a black hole represents a boundary from which nothing can escape. 
A) If we watch a clock fall toward a black hole, we will see it tick slower and slower as it falls towards the black hole. 
B) If you fell into a supermassive black hole (so that you could survive the tidal forces), you would experience time to be running normally as you plunged across the event horizon. 
C) If the Sun magically disappeared and was replaced by a black hole of the same mass, the Earth would soon be sucked into the black hole. 
D) 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 becomes more and more redshifted. 
E) The event horizon of a black hole represents a boundary from which nothing can escape.

Question 3

Suppose a white dwarf is gaining mass because of accretion from a binary companion. What happens if its mass reaches the 1.4 solar mass limit?

Accepted Answer

A) The white dwarf immediately collapses into a black hole, disappearing from view. 
B) The white dwarf undergoes a collapse and expels the excess mass in a nova eruption. 
C) A white dwarf can never gain enough mass to reach the limit because a strong stellar wind prevents the accreting material from reaching it in the first place. 
D) The white dwarf (which is made mostly of carbon)suddenly detonates carbon fusion and this creates a white dwarf supernova explosion. 
A) The white dwarf immediately collapses into a black hole, disappearing from view. 
B) The white dwarf undergoes a collapse and expels the excess mass in a nova eruption. 
C) A white dwarf can never gain enough mass to reach the limit because a strong stellar wind prevents the accreting material from reaching it in the first place. 
D) The white dwarf (which is made mostly of carbon)suddenly detonates carbon fusion and this creates a white dwarf supernova explosion.

Question 4

Pulsars are thought to be _ .

Accepted Answer

A) accreting white dwarfs 
B) unstable high- mass stars 
C) accreting black holes 
D) rapidly rotating neutron stars 
A) accreting white dwarfs 
B) unstable high- mass stars 
C) accreting black holes 
D) rapidly rotating neutron stars

Question 5

All massive- star supernovae leave behind black holes as remnants.

Accepted Answer

A) True 
 B)False

Question 6

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

Question 7

Consider an object in orbit around a star. The star suddenly shrinks in size, but does not change its mass. What happens to the object's orbit?

Accepted Answer

A) It is instantly ejected from its orbit. 
B) It gradually spirals into the star. 
C) It remains in the same orbit. 
D) It settles into a smaller orbit, with similar distance from the surface as the original orbit. 
A) It is instantly ejected from its orbit. 
B) It gradually spirals into the star. 
C) It remains in the same orbit. 
D) It settles into a smaller orbit, with similar distance from the surface as the original orbit.

Question 8

Based on current evidence, which of the following statements about gamma ray bursts is true?

Accepted Answer

A) All those that we have detected occurred in distant galaxies. 
B) All gamma ray bursts are produced by supernovae. 
C) They come primarily from the Milky Way's central black hole. 
D) They occur in the same types of close binary systems that produce X- ray bursts. 
A) All those that we have detected occurred in distant galaxies. 
B) All gamma ray bursts are produced by supernovae. 
C) They come primarily from the Milky Way's central black hole. 
D) They occur in the same types of close binary systems that produce X- ray bursts.

Question 9

A white dwarf supernova event is very important to calibrating Hubble's Law. Why? Choose the best answer for the question.

Accepted Answer

A) It is a very luminous standard candle. 
B) It is a very rare event. 
C) The white dwarf supernova in a galaxy tells us how fast a galaxy is expanding away from us. 
D) It can only happen to white dwarfs. 
A) It is a very luminous standard candle. 
B) It is a very rare event. 
C) The white dwarf supernova in a galaxy tells us how fast a galaxy is expanding away from us. 
D) It can only happen to white dwarfs.

Question 10

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

Accepted Answer

A) True 
 B)False

Question 11

Which of the following statements about novae is not true?

Accepted Answer

A) When a star system undergoes a nova, it brightens considerably, but not as much as a star system undergoing a supernova. 
B) Our Sun will probably undergo at least one nova when it becomes a white dwarf about 5 billion years from now. 
C) A star system that undergoes a nova may have another nova sometime in the future. 
D) A nova involves fusion taking place on the surface of a white dwarf. 
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) When a star system undergoes a nova, it brightens considerably, but not as much as a star system undergoing a supernova. 
B) Our Sun will probably undergo at least one nova when it becomes a white dwarf about 5 billion years from now. 
C) A star system that undergoes a nova may have another nova sometime in the future. 
D) A nova involves fusion taking place on the surface of a white dwarf. 
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 12

Studying the Singularity: The singularity at the center of a black hole is predicted to be a region of zero volume and infinite density that contains all of the black hole's mass. It is a point at which all currently known physical laws break down. Yet in a black hole, this "terrible point" is hidden from view behind an event horizon that prevents any knowledge about the singularity reaching the outside universe. Astronomers continue to spend considerable effort trying to understand the nature of these singularities, objects for which observational input, it would seem, will be forever lacking? Are these astronomers practicing science? Argue both yes and no. Which do you find convincing?

Accepted Answer

Yes, astronomers studying the nature of

Question 13

Degeneracy pressure stops the crush of gravity in all the following except

Accepted Answer

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

Question 14

A white dwarf is

Accepted Answer

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

Question 15

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

Accepted Answer

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

Question 16

Each Voyager spacecraft carries a "postcard" designed to be understandable to any aliens that might someday encounter it. On the "postcard," scientists pinpointed the location of Earth by triangulating it between pulsars. Why did the scientists choose pulsars rather than some other type of star?

Accepted Answer

A) Pulsars are very bright and therefore easy to find. 
B) We're pretty sure that aliens will have only radio telescopes and not optical telescopes, so they'll have a better chance of seeing pulsars than ordinary stars. 
C) Several pulsars are located within a dozen light- years of our solar system, making them useful for finding our solar system. 
D) Pulsars are easy to identify by their almost perfectly steady periods of pulsation. 
A) Pulsars are very bright and therefore easy to find. 
B) We're pretty sure that aliens will have only radio telescopes and not optical telescopes, so they'll have a better chance of seeing pulsars than ordinary stars. 
C) Several pulsars are located within a dozen light- years of our solar system, making them useful for finding our solar system. 
D) Pulsars are easy to identify by their almost perfectly steady periods of pulsation.

Question 17

Which of statement below 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; you'll only see him fade from view as the light he emits or reflects becomes more and more redshifted. 
B) Although we are not 100% certain that black holes exist, we have strong observational evidence in favor of their existence. 
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) 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. 
B) Although we are not 100% certain that black holes exist, we have strong observational evidence in favor of their existence. 
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 18

Order the following objects in increasing size (radius):

Accepted Answer

A) neutron star, white dwarf, Jupiter, Sun 
B) Jupiter, white dwarf, Sun, neutron star 
C) neutron star, Jupiter, white dwarf, Sun 
D) Jupiter, white dwarf, neutron star, Sun 
A) neutron star, white dwarf, Jupiter, Sun 
B) Jupiter, white dwarf, Sun, neutron star 
C) neutron star, Jupiter, white dwarf, Sun 
D) Jupiter, white dwarf, neutron star, Sun

Question 19

What is the origin of short gamma ray bursts?

Accepted Answer

A) supernovae in the Milky Way 
B) new stars forming in the Milky Way 
C) the collision of stars in the dense nuclei of distant galaxies 
D) very powerful supernovae occurring in distant galaxies 
E) It is not known, but it may be the collision of a neutron star with a black hole. 
A) supernovae in the Milky Way 
B) new stars forming in the Milky Way 
C) the collision of stars in the dense nuclei of distant galaxies 
D) very powerful supernovae occurring in distant galaxies 
E) It is not known, but it may be the collision of a neutron star with a black hole.

Question 20

Consider again the civilization described in the previous question. (They live on a planet orbiting 10 AU from a close binary star system that consists of a 15 MSun red giant star and a 10 MSun black hole surrounded by an accretion disk.)One foolhardy day, a daring individual in their space force (let's call him Major Tom)decides to become the first of his species to cross the event horizon of the black hole. To add to the drama, he decides to go in wearing only a thin space suit, which offers no shielding against radiation, no cushioning against any forces, and so on. Which of the following is most likely to kill him first (or at least to start the process of killing him first)?

Accepted Answer

A) the sucking force from the black hole, which will cause his head to explode 
B) tidal forces due to the black hole 
C) X- rays from the accretion disk 
D) the crush of gravity at the singularity embedded within the black hole 
A) the sucking force from the black hole, which will cause his head to explode 
B) tidal forces due to the black hole 
C) X- rays from the accretion disk 
D) the crush of gravity at the singularity embedded within the black hole

What causes X- ray bursters?

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

Suppose a white dwarf is gaining mass because of accretion from a binary companion. What happens if its mass reaches the 1.4 solar mass limit?

Pulsars are thought to be _ .

All massive- star supernovae leave behind black holes as remnants.

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

Consider an object in orbit around a star. The star suddenly shrinks in size, but does not change its mass. What happens to the object's orbit?

Based on current evidence, which of the following statements about gamma ray bursts is true?

A white dwarf supernova event is very important to calibrating Hubble's Law. Why? Choose the best answer for the question.

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

Which of the following statements about novae is not true?

Degeneracy pressure stops the crush of gravity in all the following except

A white dwarf is

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

Each Voyager spacecraft carries a "postcard" designed to be understandable to any aliens that might someday encounter it. On the "postcard," scientists pinpointed the location of Earth by triangulating it between pulsars. Why did the scientists choose pulsars rather than some other type of star?

Which of statement below about black holes is not true?

Order the following objects in increasing size (radius):

What is the origin of short gamma ray bursts?

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: the Cosmic Messenger

Formation of the Solar System

Earth and the Terrestrial Worlds

Jovian Planet System

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 Stuff

Our Galaxy

A Universe of Galaxies

The Birth of the Universe

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

Life in the Universe

Filters

Exam 14: The Bizarre Stellar Graveyard

What causes X- ray bursters?

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

Suppose a white dwarf is gaining mass because of accretion from a binary companion. What happens if its mass reaches the 1.4 solar mass limit?

Pulsars are thought to be _ .

All massive- star supernovae leave behind black holes as remnants.

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

Consider an object in orbit around a star. The star suddenly shrinks in size, but does not change its mass. What happens to the object's orbit?

Based on current evidence, which of the following statements about gamma ray bursts is true?

A white dwarf supernova event is very important to calibrating Hubble's Law. Why? Choose the best answer for the question.

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

Which of the following statements about novae is not true?

Degeneracy pressure stops the crush of gravity in all the following except

A white dwarf is

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

Each Voyager spacecraft carries a "postcard" designed to be understandable to any aliens that might someday encounter it. On the "postcard," scientists pinpointed the location of Earth by triangulating it between pulsars. Why did the scientists choose pulsars rather than some other type of star?

Which of statement below about black holes is not true?

Order the following objects in increasing size (radius):

What is the origin of short gamma ray bursts?

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: the Cosmic Messenger

Formation of the Solar System

Earth and the Terrestrial Worlds

Jovian Planet System

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 Stuff

Our Galaxy

A Universe of Galaxies

The Birth of the Universe

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

Life in the Universe

Filters