Question 1

What is believed to be the solar mass of the black hole candidate Cygnus X-1?

Accepted Answer

A)  120 
B)  60 
C)  15 
D)  1 
A)  120 
B)  60 
C)  15 
D)  1

Question 2

If nothing can ever leave a black hole, can the mass of a black hole ever decrease?

Accepted Answer

A)  No. 
B)  Yes, if antiparticles enter a black hole and annihilate with matter already inside the black hole. 
C)  Yes, if the matter inside the black hole is radioactive (e.g., uranium), allowing their decay products-alpha particles, electrons, and gamma rays-to constantly leave the black hole. 
D)  Yes, if particle-antiparticle pairs are created outside the event horizon out of gravitational energy from the black hole and one particle enters the event horizon while the other escapes. 
A)  No. 
B)  Yes, if antiparticles enter a black hole and annihilate with matter already inside the black hole. 
C)  Yes, if the matter inside the black hole is radioactive (e.g., uranium), allowing their decay products-alpha particles, electrons, and gamma rays-to constantly leave the black hole. 
D)  Yes, if particle-antiparticle pairs are created outside the event horizon out of gravitational energy from the black hole and one particle enters the event horizon while the other escapes.

Question 3

What would happen to the gravitational force on Earth if the Sun were to be replaced by a 1-solar-mass black hole?

Accepted Answer

A)  The gravitational force on Earth would become extremely high, sufficient to pull Earth into the black hole. 
B)  The gravitational force on Earth would double in strength. 
C)  The gravitational force on Earth would remain as it is now. 
D)  The gravitational force on Earth would be much less because the gravitational field of a black hole exists only very close to it. 
A)  The gravitational force on Earth would become extremely high, sufficient to pull Earth into the black hole. 
B)  The gravitational force on Earth would double in strength. 
C)  The gravitational force on Earth would remain as it is now. 
D)  The gravitational force on Earth would be much less because the gravitational field of a black hole exists only very close to it.

Question 4

Efforts to relate gamma-ray bursts with specific sources has had what results so far?

Accepted Answer

A)  Gamma-ray bursts always occur in the depths of space, far from any galactic or other obvious source. 
B)  Gamma-ray bursts, including those observed in the Milky Way Galaxy, always occur in the centers of galaxies. 
C)  Gamma-ray bursts appear to occur in galaxies but not at the centers of galaxies. 
D)  Gamma-ray bursts occur in globular clusters, well away from the main regions in the host galaxy. 
A)  Gamma-ray bursts always occur in the depths of space, far from any galactic or other obvious source. 
B)  Gamma-ray bursts, including those observed in the Milky Way Galaxy, always occur in the centers of galaxies. 
C)  Gamma-ray bursts appear to occur in galaxies but not at the centers of galaxies. 
D)  Gamma-ray bursts occur in globular clusters, well away from the main regions in the host galaxy.

Question 5

The X-ray source Cygnus X-1 is a black hole candidate located in a binary star system. The X-ray source is believed to occupy a volume smaller than Earth. This size is deduced from

Accepted Answer

A)  rapid flickering in the X-ray brightness of Cygnus X-1. 
B)  Cygnus X-1's apparent magnitude and distance. 
C)  Cygnus X-1's luminosity and spectral class. 
D)  the shortness of Cygnus X-1's orbital period. 
A)  rapid flickering in the X-ray brightness of Cygnus X-1. 
B)  Cygnus X-1's apparent magnitude and distance. 
C)  Cygnus X-1's luminosity and spectral class. 
D)  the shortness of Cygnus X-1's orbital period.

Question 6

What is a Schwarzschild black hole?

Accepted Answer

A)  supermassive black hole 
B)  uncharged black hole 
C)  black hole that fills its Schwarzschild radius with matter 
D)  nonrotating black hole 
A)  supermassive black hole 
B)  uncharged black hole 
C)  black hole that fills its Schwarzschild radius with matter 
D)  nonrotating black hole

Question 7

What mechanism in the vicinity of a star gives astronomers a hint of the presence of a black hole as a companion to the star?

Accepted Answer

A)  The light from the companion star shows extreme redshift because of the gravitational field of the black hole. 
B)  The star periodically disappears from the viewpoint of Earth during its eclipses by the black hole as the two objects orbit each other. 
C)  The space near the star darkens, indicating that the black hole prevents the light from distant objects from reaching Earth. 
D)  Gas from the star, falling in toward a black hole, is compressed to very high densities and temperatures so that it emits an intense and rapidly fluctuating flux of X-rays. 
A)  The light from the companion star shows extreme redshift because of the gravitational field of the black hole. 
B)  The star periodically disappears from the viewpoint of Earth during its eclipses by the black hole as the two objects orbit each other. 
C)  The space near the star darkens, indicating that the black hole prevents the light from distant objects from reaching Earth. 
D)  Gas from the star, falling in toward a black hole, is compressed to very high densities and temperatures so that it emits an intense and rapidly fluctuating flux of X-rays.

Question 8

What physical theory has been developed to describe adequately the details of what happens inside a black hole?

Accepted Answer

A)  general relativity 
B)  quantum theory 
C)  electromagnetism 
D)  None of these answers are correct. 
A)  general relativity 
B)  quantum theory 
C)  electromagnetism 
D)  None of these answers are correct.

Question 9

A child on a playground swing is swinging back and forth (one complete oscillation) once every 4 seconds, as seen by her father standing next to the swing. At the same time, a spaceship is hurtling by at a speed close to the speed of light. According to special relativity (and ignoring the Doppler effect for this question), her mother on the spaceship finds that the time for one full swing is

Accepted Answer

A)  less than 4 seconds when the spaceship is approaching the swing and more than 4 seconds when it is moving away. 
B)  less than 4 seconds. 
C)  equal to 4 seconds. 
D)  more than 4 seconds. 
A)  less than 4 seconds when the spaceship is approaching the swing and more than 4 seconds when it is moving away. 
B)  less than 4 seconds. 
C)  equal to 4 seconds. 
D)  more than 4 seconds.

Question 10

What separates a black hole from the rest of the universe?

Accepted Answer

A)  crystalline crust 
B)  surface of the ergoregion 
C)  singularity 
D)  event horizon 
A)  crystalline crust 
B)  surface of the ergoregion 
C)  singularity 
D)  event horizon

Question 11

Which of these statements is NOT a consequence of the postulates of special relativity?

Accepted Answer

A)  The mass of an object moving with respect to an observer is larger than the mass measured by a different observer who is at rest with respect to the object. 
B)  A clock moving with respect to an observer ticks more slowly than when measured by an observer who is moving along with the clock. 
C)  The length of an object moving with respect to an observer is shorter than it is when measured by a different observer moving along with the object. 
D)  The wavelength emitted from a source moving with respect to an observer is different from the wavelength measured by an observer who is moving along with the source. 
A)  The mass of an object moving with respect to an observer is larger than the mass measured by a different observer who is at rest with respect to the object. 
B)  A clock moving with respect to an observer ticks more slowly than when measured by an observer who is moving along with the clock. 
C)  The length of an object moving with respect to an observer is shorter than it is when measured by a different observer moving along with the object. 
D)  The wavelength emitted from a source moving with respect to an observer is different from the wavelength measured by an observer who is moving along with the source.

Question 12

The escape velocity at the event horizon around a black hole is

Accepted Answer

A)  infinite. 
B)  equal to the speed of light. 
C)  much less than the speed of light. 
D)  just under the speed of light. 
A)  infinite. 
B)  equal to the speed of light. 
C)  much less than the speed of light. 
D)  just under the speed of light.

Question 13

How do Kerr black holes differ from Schwarzschild black holes?

Accepted Answer

A)  Kerr black holes have infinite mass; Schwarzschild black holes do not. 
B)  Kerr black holes have net electric charge; Schwarzschild black holes do not. 
C)  Kerr black holes have accretion disks; Schwarzschild black holes do not. 
D)  Kerr black holes rotate; Schwarzschild black holes do not. 
A)  Kerr black holes have infinite mass; Schwarzschild black holes do not. 
B)  Kerr black holes have net electric charge; Schwarzschild black holes do not. 
C)  Kerr black holes have accretion disks; Schwarzschild black holes do not. 
D)  Kerr black holes rotate; Schwarzschild black holes do not.

Question 14

What is a singularity?

Accepted Answer

A)  particle-antiparticle pair 
B)  tunnel into another universe 
C)  point at the Schwarzschild radius of a black hole 
D)  point of infinite density 
A)  particle-antiparticle pair 
B)  tunnel into another universe 
C)  point at the Schwarzschild radius of a black hole 
D)  point of infinite density

Question 15

What happens to the wavelength of light as it travels outward through the gravitational field of a planet or star so that the field becomes less strong?

Accepted Answer

A)  The wavelength stays the same, but the intensity of the light decreases. 
B)  The wavelength decreases. 
C)  The wavelength stays the same, but the energy of each photon decreases. 
D)  The wavelength increases. 
A)  The wavelength stays the same, but the intensity of the light decreases. 
B)  The wavelength decreases. 
C)  The wavelength stays the same, but the energy of each photon decreases. 
D)  The wavelength increases.

Question 16

An astronaut tosses a green ball toward a Schwarzschild black hole. Which of these will NOT be observed as the ball accelerates toward the event horizon?

Accepted Answer

A)  The ball will appear green, then yellow, then red. 
B)  The ball will become elongated. 
C)  The ball's lateral size will decrease. 
D)  The ball will spin faster and faster. 
A)  The ball will appear green, then yellow, then red. 
B)  The ball will become elongated. 
C)  The ball's lateral size will decrease. 
D)  The ball will spin faster and faster.

Question 17

The X-ray source and black hole candidate LMC X-3 has a diameter of 60 km. What is the flicker frequency of its X-ray emission?

Accepted Answer

A)  2*10-5 s 
B)  0.2 ms 
C)  1.56 s 
D)  about 1 day 
A)  2*10-5 s 
B)  0.2 ms 
C)  1.56 s 
D)  about 1 day

Question 18

A spacecraft has a length of 2 meters if it is measured at rest. The spacecraft moves past an observer at half the speed of light. What will the observer measure the spacecraft's length to be?

Accepted Answer

A)  less than 10 meters 
B)  more than 10 meters 
C)  exactly 10 meters 
D)  The answer will depend on whether the observer measures the length while it is moving toward or away from them. 
A)  less than 10 meters 
B)  more than 10 meters 
C)  exactly 10 meters 
D)  The answer will depend on whether the observer measures the length while it is moving toward or away from them.

Question 19

How was the black hole candidate Cygnus X-1 first discovered?

Accepted Answer

A)  by extremely high spatial resolution radio observations with the VLA radio interferometric array in New Mexico 
B)  by high-resolution visible-light observations with the Hubble Space Telescope 
C)  by X-ray measurements with the Uhuru satellite 
D)  by infrared observations with the IRAS infrared satellite 
A)  by extremely high spatial resolution radio observations with the VLA radio interferometric array in New Mexico 
B)  by high-resolution visible-light observations with the Hubble Space Telescope 
C)  by X-ray measurements with the Uhuru satellite 
D)  by infrared observations with the IRAS infrared satellite

Question 20

If an observer were to pass inward through the event horizon of a black hole, they could

Accepted Answer

A)  do nothing to prevent themselves from falling directly into the singularity at the center. 
B)  escape again provided that the black hole is spinning. 
C)  move outward within the black hole with a powerful rocket, thereby avoiding the singularity until their fuel ran out, but they could never escape back out through the event horizon. 
D)  avoid the singularity by going into orbit around it, but they could never move outward again from any particular orbit. 
A)  do nothing to prevent themselves from falling directly into the singularity at the center. 
B)  escape again provided that the black hole is spinning. 
C)  move outward within the black hole with a powerful rocket, thereby avoiding the singularity until their fuel ran out, but they could never escape back out through the event horizon. 
D)  avoid the singularity by going into orbit around it, but they could never move outward again from any particular orbit.

What is believed to be the solar mass of the black hole candidate Cygnus X-1?

If nothing can ever leave a black hole, can the mass of a black hole ever decrease?

What would happen to the gravitational force on Earth if the Sun were to be replaced by a 1-solar-mass black hole?

Efforts to relate gamma-ray bursts with specific sources has had what results so far?

The X-ray source Cygnus X-1 is a black hole candidate located in a binary star system. The X-ray source is believed to occupy a volume smaller than Earth. This size is deduced from

What is a Schwarzschild black hole?

What mechanism in the vicinity of a star gives astronomers a hint of the presence of a black hole as a companion to the star?

What physical theory has been developed to describe adequately the details of what happens inside a black hole?

What separates a black hole from the rest of the universe?

Which of these statements is NOT a consequence of the postulates of special relativity?

The escape velocity at the event horizon around a black hole is

How do Kerr black holes differ from Schwarzschild black holes?

What is a singularity?

What happens to the wavelength of light as it travels outward through the gravitational field of a planet or star so that the field becomes less strong?

An astronaut tosses a green ball toward a Schwarzschild black hole. Which of these will NOT be observed as the ball accelerates toward the event horizon?

The X-ray source and black hole candidate LMC X-3 has a diameter of 60 km. What is the flicker frequency of its X-ray emission?

A spacecraft has a length of 2 meters if it is measured at rest. The spacecraft moves past an observer at half the speed of light. What will the observer measure the spacecraft's length to be?

How was the black hole candidate Cygnus X-1 first discovered?

If an observer were to pass inward through the event horizon of a black hole, they could

Discovering the Night Sky

Gravitation and the Motion of the Planets

Light and Telescopes

Atomic Physics and Spectra

Exoplanets and the Formation of Planetary Systems

Formation of the Solar System

Earth and the Moon

The Other Terrestrial Planets

The Outer Planets

Vagabonds of the Solar System

The Sun: Our Extraordinary Star

Characterizing Stars

The Lives of Stars From Birth Through Middle Age

The Death of Stars

The Milky Way Galaxy

Galaxies

Quasars and Other Active Galaxies

Cosmology

Astrobiology

Filters

Exam 15: Black Holes: Matters of Gravity

What is believed to be the solar mass of the black hole candidate Cygnus X-1?

If nothing can ever leave a black hole, can the mass of a black hole ever decrease?

What would happen to the gravitational force on Earth if the Sun were to be replaced by a 1-solar-mass black hole?

Efforts to relate gamma-ray bursts with specific sources has had what results so far?

The X-ray source Cygnus X-1 is a black hole candidate located in a binary star system. The X-ray source is believed to occupy a volume smaller than Earth. This size is deduced from

What is a Schwarzschild black hole?

What mechanism in the vicinity of a star gives astronomers a hint of the presence of a black hole as a companion to the star?

What physical theory has been developed to describe adequately the details of what happens inside a black hole?

What separates a black hole from the rest of the universe?

Which of these statements is NOT a consequence of the postulates of special relativity?

The escape velocity at the event horizon around a black hole is

How do Kerr black holes differ from Schwarzschild black holes?

What is a singularity?

What happens to the wavelength of light as it travels outward through the gravitational field of a planet or star so that the field becomes less strong?

An astronaut tosses a green ball toward a Schwarzschild black hole. Which of these will NOT be observed as the ball accelerates toward the event horizon?

The X-ray source and black hole candidate LMC X-3 has a diameter of 60 km. What is the flicker frequency of its X-ray emission?

A spacecraft has a length of 2 meters if it is measured at rest. The spacecraft moves past an observer at half the speed of light. What will the observer measure the spacecraft's length to be?

How was the black hole candidate Cygnus X-1 first discovered?

If an observer were to pass inward through the event horizon of a black hole, they could

Discovering the Night Sky

Gravitation and the Motion of the Planets

Light and Telescopes

Atomic Physics and Spectra

Exoplanets and the Formation of Planetary Systems

Formation of the Solar System

Earth and the Moon

The Other Terrestrial Planets

The Outer Planets

Vagabonds of the Solar System

The Sun: Our Extraordinary Star

Characterizing Stars

The Lives of Stars From Birth Through Middle Age

The Death of Stars

The Milky Way Galaxy

Galaxies

Quasars and Other Active Galaxies

Cosmology

Astrobiology

Filters