Question 1

Suppose an astronomer detects an object that displays jets of material shooting out of opposite sides. This object is probably NOT

Accepted Answer

A)  a solitary black hole with a mass of 10-100 solar masses. 
B)  a black hole in a binary system. 
C)  a neutron star in a binary system. 
D)  a supermassive black hole. 
A)  a solitary black hole with a mass of 10-100 solar masses. 
B)  a black hole in a binary system. 
C)  a neutron star in a binary system. 
D)  a supermassive black hole.

Question 2

The accretion disk surrounding a black hole is characterized by the emission of

Accepted Answer

A)  red light. 
B)  blue light. 
C)  radio waves. 
D)  X-rays. 
A)  red light. 
B)  blue light. 
C)  radio waves. 
D)  X-rays.

Question 3

A clock with a luminous dial is moving toward an observer at a speed that is a large fraction of the speed of light. Which of these will the observer measure?

Accepted Answer

A)  The light emitted by the clock will be shifted toward longer wavelengths compared to those seen by an observer moving with the clock. 
B)  The light from the clock is approaching the observer at speed c. 
C)  The clock runs fast compared to an identical clock at rest in the observer's hand. 
D)  The clock appears thicker, front to back, than the identical clock in observer's hand. 
A)  The light emitted by the clock will be shifted toward longer wavelengths compared to those seen by an observer moving with the clock. 
B)  The light from the clock is approaching the observer at speed c. 
C)  The clock runs fast compared to an identical clock at rest in the observer's hand. 
D)  The clock appears thicker, front to back, than the identical clock in observer's hand.

Question 4

In an observation of a group of stars adjacent to the limb of the Sun during a total solar eclipse, which way will the nearest star to the solar limb appear to move because of the curvature of space near the Sun?

Accepted Answer

A)  away from the Sun 
B)  toward the center of the Sun 
C)  in a direction parallel to the limb of the Sun 
D)  Light is unaffected by the curvature of space, so the star's position in the group will remain unchanged. 
A)  away from the Sun 
B)  toward the center of the Sun 
C)  in a direction parallel to the limb of the Sun 
D)  Light is unaffected by the curvature of space, so the star's position in the group will remain unchanged.

Question 5

Matter in an accretion disk is in orbit around a black hole, but friction within the disk causes the matter to gradually spiral into the black hole. What will change in terms of the observable properties of the black hole as this process continues?

Accepted Answer

A)  Only the mass will increase. 
B)  The mass, the angular momentum, and the rate of evaporation of the black hole will increase. 
C)  Nothing will change. 
D)  Both the mass and the angular momentum of the black hole will increase. 
A)  Only the mass will increase. 
B)  The mass, the angular momentum, and the rate of evaporation of the black hole will increase. 
C)  Nothing will change. 
D)  Both the mass and the angular momentum of the black hole will increase.

Question 6

Which of these is a correct and complete statement of Einstein's first postulate of special relativity?

Accepted Answer

A)  One's description of physical reality is the same regardless of the constant velocity at which one moves. 
B)  One's description of physical reality is the same regardless of the direction in which one moves, even if the speed changes. 
C)  One's description of physical reality is the same regardless of how one moves. 
D)  One's description of physical reality is the same regardless of the constant speed at which one moves, even if direction changes. 
A)  One's description of physical reality is the same regardless of the constant velocity at which one moves. 
B)  One's description of physical reality is the same regardless of the direction in which one moves, even if the speed changes. 
C)  One's description of physical reality is the same regardless of how one moves. 
D)  One's description of physical reality is the same regardless of the constant speed at which one moves, even if direction changes.

Question 7

The first direct gravitational waves to be directly observed were produced by

Accepted Answer

A)  a binary pulsar. 
B)  a black hole merger. 
C)  Type II supernovae. 
D)  gamma-ray bursts. 
A)  a binary pulsar. 
B)  a black hole merger. 
C)  Type II supernovae. 
D)  gamma-ray bursts.

Question 8

Suppose the Sun became a 1-solar-mass Schwarzschild black hole. What would be its Schwarzschild radius?

Accepted Answer

A)  2 * 10-8 au 
B)  7 * 10-3 au 
C)  5 au 
D)  3000 au 
A)  2 * 10-8 au 
B)  7 * 10-3 au 
C)  5 au 
D)  3000 au

Question 9

Which properties of the matter inside a black hole can be measured from outside the black hole?

Accepted Answer

A)  mass and angular momentum 
B)  only mass 
C)  mass, angular momentum, electric charge, and average atomic weight 
D)  mass, angular momentum, and electric charge 
A)  mass and angular momentum 
B)  only mass 
C)  mass, angular momentum, electric charge, and average atomic weight 
D)  mass, angular momentum, and electric charge

Question 10

The supermassive black hole candidate in the center of the galaxy NGC 4261 is estimated to have a mass of 1.2 * 109 MSun. What is the Schwarzschild radius of this black hole?

Accepted Answer

A)  1.6* 109 meters, a little larger than the Sun 
B)  24 au, a little larger than Jupiter's orbit 
C)  0.95 pc, more than half the distance to the nearest star 
D)  1600 pc, about one-tenth of the way across the Milky Way Galaxy 
A)  1.6* 109 meters, a little larger than the Sun 
B)  24 au, a little larger than Jupiter's orbit 
C)  0.95 pc, more than half the distance to the nearest star 
D)  1600 pc, about one-tenth of the way across the Milky Way Galaxy

Question 11

In general, how many fundamentally different types of black holes are expected to exist?

Accepted Answer

A)  only one-all properties but mass are destroyed when a black hole is created 
B)  two-those that have electric charge and those that have no electric charge 
C)  three-atomic-mass black holes, stellar-mass black holes, and supermassive black holes 
D)  two-those that rotate and those that do not rotate 
A)  only one-all properties but mass are destroyed when a black hole is created 
B)  two-those that have electric charge and those that have no electric charge 
C)  three-atomic-mass black holes, stellar-mass black holes, and supermassive black holes 
D)  two-those that rotate and those that do not rotate

Question 12

Why does Einstein's theory of special relativity carry the name "special"?

Accepted Answer

A)  The theory deals only with motion at speeds significantly less than the speed of light. 
B)  The theory deals only with objects that are at rest relative to each other. 
C)  The theory deals only with gravity, not with other kinds of forces. 
D)  The theory deals only with objects moving in a straight line at a constant speed. 
A)  The theory deals only with motion at speeds significantly less than the speed of light. 
B)  The theory deals only with objects that are at rest relative to each other. 
C)  The theory deals only with gravity, not with other kinds of forces. 
D)  The theory deals only with objects moving in a straight line at a constant speed.

Question 13

What is the likely final fate of a star of 30 solar masses when it is on the main sequence?

Accepted Answer

A)  The star will collapse and become a black hole. 
B)  The star will condense to the point where it is composed completely of neutrons, the degeneracy of which will prevent further shrinkage. 
C)  The degeneracy of the electrons within the star will prevent collapse below the diameter of a white dwarf. 
D)  The star will immediately split in two and become a binary star system. 
A)  The star will collapse and become a black hole. 
B)  The star will condense to the point where it is composed completely of neutrons, the degeneracy of which will prevent further shrinkage. 
C)  The degeneracy of the electrons within the star will prevent collapse below the diameter of a white dwarf. 
D)  The star will immediately split in two and become a binary star system.

Question 14

For typical gravitational waves generated by black hole mergers, how large is the distortion on a rod 1 meter long?

Accepted Answer

A)  10-20 m 
B)  10-10 m 
C)  10-5 m 
D)  10-2 m 
A)  10-20 m 
B)  10-10 m 
C)  10-5 m 
D)  10-2 m

Question 15

Suppose it were possible to lower a yellow sodium lamp toward the event horizon of a black hole. What would an observer see while watching from a safe distance?

Accepted Answer

A)  The brightness and color would each remain unchanged. 
B)  The light from the lamp would change to orange and then red. 
C)  The light would remain yellow, but there would be fewer and fewer photons being emitted from it. 
D)  The light from the lamp would change to green and then blue. 
A)  The brightness and color would each remain unchanged. 
B)  The light from the lamp would change to orange and then red. 
C)  The light would remain yellow, but there would be fewer and fewer photons being emitted from it. 
D)  The light from the lamp would change to green and then blue.

Question 16

Suppose astronauts are in a spaceship traveling toward Earth at 95% of the speed of light. Compared with when the ship was at rest on Mars, what length do the astronauts measure for their spaceship?

Accepted Answer

A)  It cannot be determined; their life processes have slowed down too much for them to measure the length. 
B)  same 
C)  shorter 
D)  longer 
A)  It cannot be determined; their life processes have slowed down too much for them to measure the length. 
B)  same 
C)  shorter 
D)  longer

Question 17

If a black hole is truly black and the escape velocity associated with it is greater than the speed of light such that no light can escape it, where do the X-rays from the black hole candidates so far identified originate?

Accepted Answer

A)  The black hole is only black to visible radiation, but X-rays travel faster than the speed of light and so can escape. 
B)  The X-rays originate from the normal star accompanying the black hole; its ordinary light is blueshifted into the X-ray spectral region by the intense gravity of the black hole. 
C)  The X-rays originate from stars behind the black hole, the light from which is focused and concentrated such that it becomes X-ray radiation by gravitational focusing. 
D)  The X-rays originate from the matter surrounding the black hole that is highly condensed and hence very hot because of the intense gravitational field. 
A)  The black hole is only black to visible radiation, but X-rays travel faster than the speed of light and so can escape. 
B)  The X-rays originate from the normal star accompanying the black hole; its ordinary light is blueshifted into the X-ray spectral region by the intense gravity of the black hole. 
C)  The X-rays originate from stars behind the black hole, the light from which is focused and concentrated such that it becomes X-ray radiation by gravitational focusing. 
D)  The X-rays originate from the matter surrounding the black hole that is highly condensed and hence very hot because of the intense gravitational field.

Question 18

The only physical properties that are necessary to describe a black hole and its interaction with the rest of the universe completely are

Accepted Answer

A)  total mass, total angular momentum or spin, and temperature. 
B)  total mass, chemical or atomic structure of the matter within it, and overall size. 
C)  size of the event horizon, strength of its magnetic field, and size of its solid core. 
D)  total mass, total electric charge, and total angular momentum or spin. 
A)  total mass, total angular momentum or spin, and temperature. 
B)  total mass, chemical or atomic structure of the matter within it, and overall size. 
C)  size of the event horizon, strength of its magnetic field, and size of its solid core. 
D)  total mass, total electric charge, and total angular momentum or spin.

Question 19

The intense X-rays emitted by a suspected black hole are generated by what physical mechanism?

Accepted Answer

A)  blueshifting of light emitted by hot gas into the X-ray region of the electromagnetic spectrum by the extreme speed of the gas moving into the black hole 
B)  induced emission in atoms by the intense gravitational field as material moves toward the black hole 
C)  compressional heating as material moves into the black hole 
D)  deceleration of matter as it abruptly stops at the event horizon of the black hole 
A)  blueshifting of light emitted by hot gas into the X-ray region of the electromagnetic spectrum by the extreme speed of the gas moving into the black hole 
B)  induced emission in atoms by the intense gravitational field as material moves toward the black hole 
C)  compressional heating as material moves into the black hole 
D)  deceleration of matter as it abruptly stops at the event horizon of the black hole

Question 20

What is the observed distribution of the longer-living gamma-ray bursts in the sky?

Accepted Answer

A)  concentrated primarily along the plane of the Milky Way, indicating an origin in the Galaxy 
B)  uniform over the entire sky, indicating an origin outside of the Milky Way 
C)  clumpy but not coinciding with any known galaxy clusters, indicating an origin in a new kind of astronomical object 
D)  clumpy, approximately coinciding with large clusters of galaxies such as the Coma cluster 
A)  concentrated primarily along the plane of the Milky Way, indicating an origin in the Galaxy 
B)  uniform over the entire sky, indicating an origin outside of the Milky Way 
C)  clumpy but not coinciding with any known galaxy clusters, indicating an origin in a new kind of astronomical object 
D)  clumpy, approximately coinciding with large clusters of galaxies such as the Coma cluster

Suppose an astronomer detects an object that displays jets of material shooting out of opposite sides. This object is probably NOT

The accretion disk surrounding a black hole is characterized by the emission of

A clock with a luminous dial is moving toward an observer at a speed that is a large fraction of the speed of light. Which of these will the observer measure?

In an observation of a group of stars adjacent to the limb of the Sun during a total solar eclipse, which way will the nearest star to the solar limb appear to move because of the curvature of space near the Sun?

Matter in an accretion disk is in orbit around a black hole, but friction within the disk causes the matter to gradually spiral into the black hole. What will change in terms of the observable properties of the black hole as this process continues?

Which of these is a correct and complete statement of Einstein's first postulate of special relativity?

The first direct gravitational waves to be directly observed were produced by

Suppose the Sun became a 1-solar-mass Schwarzschild black hole. What would be its Schwarzschild radius?

Which properties of the matter inside a black hole can be measured from outside the black hole?

The supermassive black hole candidate in the center of the galaxy NGC 4261 is estimated to have a mass of 1.2 * 10⁹ M_Sun. What is the Schwarzschild radius of this black hole?

In general, how many fundamentally different types of black holes are expected to exist?

Why does Einstein's theory of special relativity carry the name "special"?

What is the likely final fate of a star of 30 solar masses when it is on the main sequence?

For typical gravitational waves generated by black hole mergers, how large is the distortion on a rod 1 meter long?

Suppose it were possible to lower a yellow sodium lamp toward the event horizon of a black hole. What would an observer see while watching from a safe distance?

Suppose astronauts are in a spaceship traveling toward Earth at 95% of the speed of light. Compared with when the ship was at rest on Mars, what length do the astronauts measure for their spaceship?

If a black hole is truly black and the escape velocity associated with it is greater than the speed of light such that no light can escape it, where do the X-rays from the black hole candidates so far identified originate?

The only physical properties that are necessary to describe a black hole and its interaction with the rest of the universe completely are

The intense X-rays emitted by a suspected black hole are generated by what physical mechanism?

What is the observed distribution of the longer-living gamma-ray bursts in the sky?

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

Suppose an astronomer detects an object that displays jets of material shooting out of opposite sides. This object is probably NOT

The accretion disk surrounding a black hole is characterized by the emission of

A clock with a luminous dial is moving toward an observer at a speed that is a large fraction of the speed of light. Which of these will the observer measure?

In an observation of a group of stars adjacent to the limb of the Sun during a total solar eclipse, which way will the nearest star to the solar limb appear to move because of the curvature of space near the Sun?

Matter in an accretion disk is in orbit around a black hole, but friction within the disk causes the matter to gradually spiral into the black hole. What will change in terms of the observable properties of the black hole as this process continues?

Which of these is a correct and complete statement of Einstein's first postulate of special relativity?

The first direct gravitational waves to be directly observed were produced by

Suppose the Sun became a 1-solar-mass Schwarzschild black hole. What would be its Schwarzschild radius?

Which properties of the matter inside a black hole can be measured from outside the black hole?

The supermassive black hole candidate in the center of the galaxy NGC 4261 is estimated to have a mass of 1.2 * 109 MSun. What is the Schwarzschild radius of this black hole?

In general, how many fundamentally different types of black holes are expected to exist?

Why does Einstein's theory of special relativity carry the name "special"?

What is the likely final fate of a star of 30 solar masses when it is on the main sequence?

For typical gravitational waves generated by black hole mergers, how large is the distortion on a rod 1 meter long?

Suppose it were possible to lower a yellow sodium lamp toward the event horizon of a black hole. What would an observer see while watching from a safe distance?

Suppose astronauts are in a spaceship traveling toward Earth at 95% of the speed of light. Compared with when the ship was at rest on Mars, what length do the astronauts measure for their spaceship?

If a black hole is truly black and the escape velocity associated with it is greater than the speed of light such that no light can escape it, where do the X-rays from the black hole candidates so far identified originate?

The only physical properties that are necessary to describe a black hole and its interaction with the rest of the universe completely are

The intense X-rays emitted by a suspected black hole are generated by what physical mechanism?

What is the observed distribution of the longer-living gamma-ray bursts in the sky?

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

The supermassive black hole candidate in the center of the galaxy NGC 4261 is estimated to have a mass of 1.2 * 10⁹ M_Sun. What is the Schwarzschild radius of this black hole?