Question 1

How does a gravitational field affect the passage of time?

Accepted Answer

A)  Gravity has no effect on the passage of time. 
B)  Clocks in a gravitational field run slower than clocks farther from the center of the field when viewed by an observer who is also farther from the center of the field. 
C)  Gravity makes time stop. 
D)  Clocks in a gravitational field run faster than clocks farther from the center of the field when viewed by an observer who is also farther from the center of the field. 
A)  Gravity has no effect on the passage of time. 
B)  Clocks in a gravitational field run slower than clocks farther from the center of the field when viewed by an observer who is also farther from the center of the field. 
C)  Gravity makes time stop. 
D)  Clocks in a gravitational field run faster than clocks farther from the center of the field when viewed by an observer who is also farther from the center of the field.

Question 2

Two spaceships are traveling past Earth at 90% of the speed of light in opposite directions (i.e., they are approaching each other). One spaceship turns on a searchlight, which is seen by scientists aboard the other. What speed do the scientists measure for this light (c = speed of light in a vacuum)?

Accepted Answer

A)  1.9 c (equal to c + 0.9 c) 
B)  1.8 c (equal to 2 *0.9 c). 
C)  c 
D)  0.9 c 
A)  1.9 c (equal to c + 0.9 c) 
B)  1.8 c (equal to 2 *0.9 c). 
C)  c 
D)  0.9 c

Question 3

The black hole at the center of the galaxy M87 is estimated to have a mass of 3 * 109 MSun. Suppose the orbits of the stars observed circling it have semimajor axes of 50 au. Approximately what would be the period of their orbital motion?

Accepted Answer

A)  3 seconds 
B)  24 days 
C)  7 years 
D)  127 years 
A)  3 seconds 
B)  24 days 
C)  7 years 
D)  127 years

Question 4

X-rays that come from the vicinity of a black hole actually originate from

Accepted Answer

A)  just outside the event horizon, on the accretion disk. 
B)  the exact center, or singularity, of the black hole. 
C)  relatively far away from the black hole, where matter is quite cool. 
D)  well inside the event horizon. 
A)  just outside the event horizon, on the accretion disk. 
B)  the exact center, or singularity, of the black hole. 
C)  relatively far away from the black hole, where matter is quite cool. 
D)  well inside the event horizon.

Question 5

Which of these statements does NOT correctly compares gamma-ray bursts with X-ray bursts?

Accepted Answer

A)  Gamma-ray bursts occur only once. X-ray bursts can repeat. 
B)  Gamma-ray bursts originate all over the sky. X-ray bursts come mostly from the galactic plane. 
C)  In general, gamma-ray bursts carry less energy than X-ray bursts. 
D)  Gamma-ray bursts appear to originate at the beginning of a supernova explosion. X-ray bursts originate in binary systems. 
A)  Gamma-ray bursts occur only once. X-ray bursts can repeat. 
B)  Gamma-ray bursts originate all over the sky. X-ray bursts come mostly from the galactic plane. 
C)  In general, gamma-ray bursts carry less energy than X-ray bursts. 
D)  Gamma-ray bursts appear to originate at the beginning of a supernova explosion. X-ray bursts originate in binary systems.

Question 6

Which of these techniques has been successful in identifying good candidates for a black hole in the Milky Way Galaxy?

Accepted Answer

A)  detection of extremely redshifted starlight from a region in the nearby spiral arm of the Galaxy 
B)  detection of X-rays from a binary star undergoing mass exchange, where masses of component stars can be determined 
C)  detection of an extremely dark point in the sky from which no light at all is seen 
D)  gravitational lensing of light from a distant object by the black hole to produce two identical images 
A)  detection of extremely redshifted starlight from a region in the nearby spiral arm of the Galaxy 
B)  detection of X-rays from a binary star undergoing mass exchange, where masses of component stars can be determined 
C)  detection of an extremely dark point in the sky from which no light at all is seen 
D)  gravitational lensing of light from a distant object by the black hole to produce two identical images

Question 7

In what way is the general theory of relativity more "general" (i.e., deals with more situations) than the special theory of relativity?

Accepted Answer

A)  The general theory includes gravitation and accelerated motion. 
B)  The general theory includes the change in the rate of passage of time when objects are in motion. 
C)  The general theory includes motion at and above the speed of light. 
D)  The general theory includes only constant, unaccelerated motion. 
A)  The general theory includes gravitation and accelerated motion. 
B)  The general theory includes the change in the rate of passage of time when objects are in motion. 
C)  The general theory includes motion at and above the speed of light. 
D)  The general theory includes only constant, unaccelerated motion.

Question 8

What is the distance from the center to the event horizon of a nonrotating black hole with the mass of Earth?

Accepted Answer

A)  8.5 * 10-7 m 
B)  9 mm 
C)  1.5 m 
D)  6 km 
A)  8.5 * 10-7 m 
B)  9 mm 
C)  1.5 m 
D)  6 km

Question 9

A student is on Mars standing on the gangplank of a spaceship when she sees an identical spaceship go past Mars at 90% of the speed of light. When she looks closely at this spaceship, how does it compare with her own spaceship?

Accepted Answer

A)  The moving spaceship appears to be shorter than hers, and time on it appears to move more slowly than on her ship. 
B)  The moving spaceship appears to be shorter than hers, and time on it appears to move more quickly than on her ship. 
C)  The moving spaceship appears to be longer than hers, and time on it appears to move more quickly than on her ship. 
D)  The moving spaceship appears to be longer than hers, and time on it appears to move more slowly than on her ship. 
A)  The moving spaceship appears to be shorter than hers, and time on it appears to move more slowly than on her ship. 
B)  The moving spaceship appears to be shorter than hers, and time on it appears to move more quickly than on her ship. 
C)  The moving spaceship appears to be longer than hers, and time on it appears to move more quickly than on her ship. 
D)  The moving spaceship appears to be longer than hers, and time on it appears to move more slowly than on her ship.

Question 10

In the context of black holes, a singularity is a(n)

Accepted Answer

A)  place just outside the event horizon of a rotating black hole where it is impossible to remain at rest. 
B)  entry point in the event horizon of a black hole through which material is allowed to pass unhindered. 
C)  place where a nonzero mass occupies zero volume. 
D)  place where the escape velocity exactly equals the speed of light. 
A)  place just outside the event horizon of a rotating black hole where it is impossible to remain at rest. 
B)  entry point in the event horizon of a black hole through which material is allowed to pass unhindered. 
C)  place where a nonzero mass occupies zero volume. 
D)  place where the escape velocity exactly equals the speed of light.

Question 11

Gravitational waves are

Accepted Answer

A)  instabilities generating cosmic rays. 
B)  ripples in the fabric of spacetime. 
C)  structures on the event horizon of a black hole. 
D)  tidal forces that elongate objects falling into black holes. 
A)  instabilities generating cosmic rays. 
B)  ripples in the fabric of spacetime. 
C)  structures on the event horizon of a black hole. 
D)  tidal forces that elongate objects falling into black holes.

Question 12

What happens to the magnetic field of a star that collapses completely to become a black hole?

Accepted Answer

A)  The magnetic field becomes infinitely intensified. 
B)  The magnetic field must be radiated away; black holes never have magnetic fields. 
C)  The magnetic field becomes compressed and intensified by a factor equal to the ratio of the star's original diameter to the diameter of the event horizon. 
D)  The magnetic field becomes weaker by the ratio of the diameter of the black hole event horizon to the star's original diameter. 
A)  The magnetic field becomes infinitely intensified. 
B)  The magnetic field must be radiated away; black holes never have magnetic fields. 
C)  The magnetic field becomes compressed and intensified by a factor equal to the ratio of the star's original diameter to the diameter of the event horizon. 
D)  The magnetic field becomes weaker by the ratio of the diameter of the black hole event horizon to the star's original diameter.

Question 13

What is it that is actually located at the event horizon of a black hole?

Accepted Answer

A)  infinitely dense concentration of mass 
B)  magnetic field of immense strength 
C)  nothing specific 
D)  sphere of photons 
A)  infinitely dense concentration of mass 
B)  magnetic field of immense strength 
C)  nothing specific 
D)  sphere of photons

Question 14

Which of these measurements is the lower limit for a main-sequence star that will eventually form a black hole?

Accepted Answer

A)  50 solar masses 
B)  25 solar masses 
C)  3 solar masses 
D)  1.4 solar masses 
A)  50 solar masses 
B)  25 solar masses 
C)  3 solar masses 
D)  1.4 solar masses

Question 15

Why is Cygnus X-1 thought to be a black hole?

Accepted Answer

A)  Cygnus X-1 emits X-rays that flicker on timescales of 1/100 second, a unique characteristic of a black hole. 
B)  No light has ever been observed to come from Cygnus X-1. 
C)  Cygnus X-1 is smaller than Earth, but its mass is too large to be a neutron star or white dwarf. 
D)  Cygnus X-1 has pulled matter from its companion star into an accretion disk around itself. 
A)  Cygnus X-1 emits X-rays that flicker on timescales of 1/100 second, a unique characteristic of a black hole. 
B)  No light has ever been observed to come from Cygnus X-1. 
C)  Cygnus X-1 is smaller than Earth, but its mass is too large to be a neutron star or white dwarf. 
D)  Cygnus X-1 has pulled matter from its companion star into an accretion disk around itself.

Question 16

If the Sun were replaced by a 1-solar-mass black hole, then Earth would

Accepted Answer

A)  enter an elliptical orbit passing close to the black hole, with its farthest distance from the black hole equal to 1 au. 
B)  spiral quickly into the black hole. 
C)  head off into interstellar space along a straight-line tangent to its original orbit around the Sun. 
D)  continue to orbit the black hole in its present orbit. 
A)  enter an elliptical orbit passing close to the black hole, with its farthest distance from the black hole equal to 1 au. 
B)  spiral quickly into the black hole. 
C)  head off into interstellar space along a straight-line tangent to its original orbit around the Sun. 
D)  continue to orbit the black hole in its present orbit.

Question 17

Einstein's theory of special relativity contains some very strange ideas such as time dilation (moving clocks run slow), length contraction (moving lengths are shorter), and lack of absolute simultaneity. What is the basis of these ideas?

Accepted Answer

A)  New technologies allow more precise measurements of length and time than had been possible in Newton's era, and the theory had to be reworked to fit this new evidence. 
B)  The speed of light is the same for all observers in all reference frames. 
C)  The ether (the medium that supports the passage of light) proved to be denser than originally thought. 
D)  The fabric of spacetime is dominated by black holes. 
A)  New technologies allow more precise measurements of length and time than had been possible in Newton's era, and the theory had to be reworked to fit this new evidence. 
B)  The speed of light is the same for all observers in all reference frames. 
C)  The ether (the medium that supports the passage of light) proved to be denser than originally thought. 
D)  The fabric of spacetime is dominated by black holes.

Question 18

If Alice stays on Earth while Bob races off in a rocket at a speed close to the speed of light, then, according to special relativity Alice will see a clock on the rocket appear to tick more slowly than the one on her wall. If Bob looks back at Alice's wall clock, then according to the same theory Bob will see the wall clock appear to tick

Accepted Answer

A)  at the same speed as the clock on the rocket. 
B)  faster than the clock on the rocket. 
C)  faster or slower than the clock on the rocket, depending on the direction of travel of the rocket compared with Earth. 
D)  slower than the clock on the rocket. 
A)  at the same speed as the clock on the rocket. 
B)  faster than the clock on the rocket. 
C)  faster or slower than the clock on the rocket, depending on the direction of travel of the rocket compared with Earth. 
D)  slower than the clock on the rocket.

Question 19

A compact body pulls material from a binary companion. This material plunges toward the compact body and emits X-rays. Which of these phenomena would this description NOT fit?

Accepted Answer

A)  pulsating X-ray source 
B)  X-ray burster 
C)  black hole in a binary system 
D)  nova 
A)  pulsating X-ray source 
B)  X-ray burster 
C)  black hole in a binary system 
D)  nova

Question 20

What is the Schwarzschild radius of a 2-solar-mass black hole?

Accepted Answer

A)  60 km 
B)  6000 km 
C)  6 m 
D)  6 km 
A)  60 km 
B)  6000 km 
C)  6 m 
D)  6 km

How does a gravitational field affect the passage of time?

The black hole at the center of the galaxy M87 is estimated to have a mass of 3 * 10⁹ M_Sun. Suppose the orbits of the stars observed circling it have semimajor axes of 50 au. Approximately what would be the period of their orbital motion?

X-rays that come from the vicinity of a black hole actually originate from

Which of these statements does NOT correctly compares gamma-ray bursts with X-ray bursts?

Which of these techniques has been successful in identifying good candidates for a black hole in the Milky Way Galaxy?

In what way is the general theory of relativity more "general" (i.e., deals with more situations) than the special theory of relativity?

What is the distance from the center to the event horizon of a nonrotating black hole with the mass of Earth?

A student is on Mars standing on the gangplank of a spaceship when she sees an identical spaceship go past Mars at 90% of the speed of light. When she looks closely at this spaceship, how does it compare with her own spaceship?

In the context of black holes, a singularity is a(n)

Gravitational waves are

What happens to the magnetic field of a star that collapses completely to become a black hole?

What is it that is actually located at the event horizon of a black hole?

Which of these measurements is the lower limit for a main-sequence star that will eventually form a black hole?

Why is Cygnus X-1 thought to be a black hole?

If the Sun were replaced by a 1-solar-mass black hole, then Earth would

Einstein's theory of special relativity contains some very strange ideas such as time dilation (moving clocks run slow), length contraction (moving lengths are shorter), and lack of absolute simultaneity. What is the basis of these ideas?

A compact body pulls material from a binary companion. This material plunges toward the compact body and emits X-rays. Which of these phenomena would this description NOT fit?

What is the Schwarzschild radius of a 2-solar-mass black hole?

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

How does a gravitational field affect the passage of time?

The black hole at the center of the galaxy M87 is estimated to have a mass of 3 * 109 MSun. Suppose the orbits of the stars observed circling it have semimajor axes of 50 au. Approximately what would be the period of their orbital motion?

X-rays that come from the vicinity of a black hole actually originate from

Which of these statements does NOT correctly compares gamma-ray bursts with X-ray bursts?

Which of these techniques has been successful in identifying good candidates for a black hole in the Milky Way Galaxy?

In what way is the general theory of relativity more "general" (i.e., deals with more situations) than the special theory of relativity?

What is the distance from the center to the event horizon of a nonrotating black hole with the mass of Earth?

A student is on Mars standing on the gangplank of a spaceship when she sees an identical spaceship go past Mars at 90% of the speed of light. When she looks closely at this spaceship, how does it compare with her own spaceship?

In the context of black holes, a singularity is a(n)

Gravitational waves are

What happens to the magnetic field of a star that collapses completely to become a black hole?

What is it that is actually located at the event horizon of a black hole?

Which of these measurements is the lower limit for a main-sequence star that will eventually form a black hole?

Why is Cygnus X-1 thought to be a black hole?

If the Sun were replaced by a 1-solar-mass black hole, then Earth would

Einstein's theory of special relativity contains some very strange ideas such as time dilation (moving clocks run slow), length contraction (moving lengths are shorter), and lack of absolute simultaneity. What is the basis of these ideas?

A compact body pulls material from a binary companion. This material plunges toward the compact body and emits X-rays. Which of these phenomena would this description NOT fit?

What is the Schwarzschild radius of a 2-solar-mass black hole?

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 black hole at the center of the galaxy M87 is estimated to have a mass of 3 * 10⁹ M_Sun. Suppose the orbits of the stars observed circling it have semimajor axes of 50 au. Approximately what would be the period of their orbital motion?