Question 1

What appears to happen to a clock as it approaches and reaches the event horizon around a black hole when viewed by a remote observer?

Accepted Answer

A)  Time appears to pass at a much faster rate, becoming infinitely fast at the event horizon. 
B)  Time appears to slow down and stop. 
C)  Time speeds up because of the intensified gravitational field. 
D)  Time ticks uniformly since nothing changes the progress of time. 
A)  Time appears to pass at a much faster rate, becoming infinitely fast at the event horizon. 
B)  Time appears to slow down and stop. 
C)  Time speeds up because of the intensified gravitational field. 
D)  Time ticks uniformly since nothing changes the progress of time.

Question 2

What is Hawking radiation?

Accepted Answer

A)  microwaves from the edge of the visible universe 
B)  electromagnetic radiation from electrons spiraling in the magnetosphere of a neutron star 
C)  stream of particles and antiparticles from just outside the event horizon of a black hole 
D)  X-rays from an accretion disk around a black hole 
A)  microwaves from the edge of the visible universe 
B)  electromagnetic radiation from electrons spiraling in the magnetosphere of a neutron star 
C)  stream of particles and antiparticles from just outside the event horizon of a black hole 
D)  X-rays from an accretion disk around a black hole

Question 3

Suppose that a clock is carefully calibrated to tick at a regular rate. If one is brought inside a strong gravitational field, an observer far from that gravitational field would measure the clock to tick

Accepted Answer

A)  at the same rate in a gravitational field if it is an atomic clock but at a slower rate if it is a mechanical clock. 
B)  at the same rate, wherever it is placed in a gravitational field. 
C)  slower the closer it comes to the source of gravity. 
D)  faster the closer it comes to the source of gravity. 
A)  at the same rate in a gravitational field if it is an atomic clock but at a slower rate if it is a mechanical clock. 
B)  at the same rate, wherever it is placed in a gravitational field. 
C)  slower the closer it comes to the source of gravity. 
D)  faster the closer it comes to the source of gravity.

Question 4

How much energy does a typical longer-living gamma-ray burst emit in 100 seconds?

Accepted Answer

A)  as much as the Sun in 100 years 
B)  as much as the Sun in a month 
C)  as much as the Sun since the demise of the dinosaurs 
D)  as much as the Sun over its entire lifetime 
A)  as much as the Sun in 100 years 
B)  as much as the Sun in a month 
C)  as much as the Sun since the demise of the dinosaurs 
D)  as much as the Sun over its entire lifetime

Question 5

Supposedly nothing can escape from a black hole, yet astronomers are locating black hole candidates by the X-rays they emit. How can X-rays be coming from a black hole?

Accepted Answer

A)  The X-rays come from a highly compressed region in an accretion disk outside the event horizon of the black hole. 
B)  X-rays are not light or matter and can therefore escape from inside the black hole. 
C)  If the black hole is rotating, it modifies spacetime around it so much that particles and X-rays are created in the vacuum just outside the event horizon. 
D)  The X-rays are produced by vibrations of the black hole itself and therefore do not come from inside the black hole. 
A)  The X-rays come from a highly compressed region in an accretion disk outside the event horizon of the black hole. 
B)  X-rays are not light or matter and can therefore escape from inside the black hole. 
C)  If the black hole is rotating, it modifies spacetime around it so much that particles and X-rays are created in the vacuum just outside the event horizon. 
D)  The X-rays are produced by vibrations of the black hole itself and therefore do not come from inside the black hole.

Question 6

Gamma-ray bursts are at great distances from Earth, yet Earth receives tremendous amounts of energy from them. Explain.

Accepted Answer

A)  Gamma-ray bursts are supermassive stars, equivalent to 100,000 ordinary supernovae. 
B)  A gamma-ray burst represents the explosion of an entire galaxy. 
C)  The energy is released along jets rather than uniformly in all directions. If Earth is in the path of one of these jets, a gamma-ray burst is observed. 
D)  The gamma radiation from a burst is released in all directions, but then it is focused in the direction of Earth by gravitational lensing. 
A)  Gamma-ray bursts are supermassive stars, equivalent to 100,000 ordinary supernovae. 
B)  A gamma-ray burst represents the explosion of an entire galaxy. 
C)  The energy is released along jets rather than uniformly in all directions. If Earth is in the path of one of these jets, a gamma-ray burst is observed. 
D)  The gamma radiation from a burst is released in all directions, but then it is focused in the direction of Earth by gravitational lensing.

Question 7

An electromagnetic wave leaves the surface of a neutron star and travels outward. As the wave gets farther from the star's surface, the _____ and the _____.

Accepted Answer

A)  speed decreases; wavelength increases 
B)  frequency increases; wavelength decreases 
C)  frequency decreases; wavelength increases 
D)  speed decreases; frequency decreases 
A)  speed decreases; wavelength increases 
B)  frequency increases; wavelength decreases 
C)  frequency decreases; wavelength increases 
D)  speed decreases; frequency decreases

Question 8

At which of these locations will Newton's laws of motion be MOST inadequate in describing precisely the motions of objects?

Accepted Answer

A)  in the Space Shuttle, moving around Earth at a speed of about 8 km/sec 
B)  at the center of Earth 
C)  inside an artillery shell as it accelerates inside the gun barrel 
D)  inside the orbit of Mercury 
A)  in the Space Shuttle, moving around Earth at a speed of about 8 km/sec 
B)  at the center of Earth 
C)  inside an artillery shell as it accelerates inside the gun barrel 
D)  inside the orbit of Mercury

Question 9

What is a Kerr black hole?

Accepted Answer

A)  nonrotating black hole 
B)  rotating black hole 
C)  uncharged black hole 
D)  hypothetical zero-mass black hole 
A)  nonrotating black hole 
B)  rotating black hole 
C)  uncharged black hole 
D)  hypothetical zero-mass black hole

Question 10

What is a superstring?

Accepted Answer

A)  new kind of force postulated to keep a companion binary star from falling into a black hole 
B)  line of material along which the jets shoot out from neutron stars and black holes 
C)  new theory of physics that may describe what happens inside the event horizon of a black hole 
D)  force that holds quarks together in a quark star 
A)  new kind of force postulated to keep a companion binary star from falling into a black hole 
B)  line of material along which the jets shoot out from neutron stars and black holes 
C)  new theory of physics that may describe what happens inside the event horizon of a black hole 
D)  force that holds quarks together in a quark star

Question 11

What happens to a photon that leaves the interior of a black hole aimed directly upward (radially outward)?

Accepted Answer

A)  This photon will be stopped and pulled back downward by the gravity of the black hole. 
B)  Since symmetry prohibits this photon from deflecting to either side, this is the only case in which a photon can escape from a black hole. But since it must be aimed precisely upward, this is a vanishingly small fraction of all the light inside the black hole. 
C)  This photon reflects from the ergoregion back to the singularity where it is absorbed. 
D)  This photon becomes infinitely redshifted and loses all its energy. 
A)  This photon will be stopped and pulled back downward by the gravity of the black hole. 
B)  Since symmetry prohibits this photon from deflecting to either side, this is the only case in which a photon can escape from a black hole. But since it must be aimed precisely upward, this is a vanishingly small fraction of all the light inside the black hole. 
C)  This photon reflects from the ergoregion back to the singularity where it is absorbed. 
D)  This photon becomes infinitely redshifted and loses all its energy.

Question 12

How was the mass of the candidate black hole at the center of the galaxy M87 estimated?

Accepted Answer

A)  from the amount of mass that is disappearing into it every year 
B)  from the periodic shift in the wavelengths of spectral lines from a companion object around which the black hole is orbiting 
C)  from observations of the very high orbital speed of objects close to this center 
D)  from the intensity of X-rays emitted from it and the frequency of the flickering of the X-ray intensity 
A)  from the amount of mass that is disappearing into it every year 
B)  from the periodic shift in the wavelengths of spectral lines from a companion object around which the black hole is orbiting 
C)  from observations of the very high orbital speed of objects close to this center 
D)  from the intensity of X-rays emitted from it and the frequency of the flickering of the X-ray intensity

Question 13

Suppose that a large piece (e.g., 5 solar masses) of purple, magnetized iron is rotating 5 times per day. If this object were able to collapse gravitationally to form a black hole, which of these properties of the matter inside the black hole could an outside observer actually measure?

Accepted Answer

A)  rotation 
B)  magnetic field 
C)  color 
D)  composition 
A)  rotation 
B)  magnetic field 
C)  color 
D)  composition

Question 14

Light leaving the surface of a neutron star is strongly redshifted. What name is given to this effect?

Accepted Answer

A)  cosmological redshift 
B)  gravitational redshift 
C)  Zeeman effect 
D)  Doppler shift 
A)  cosmological redshift 
B)  gravitational redshift 
C)  Zeeman effect 
D)  Doppler shift

Question 15

Fred and Joanne both measure the length of a particular spaceship to be 100 m when it is on Earth. Joanne then gets into the spaceship and, after visiting the Moon, hurtles past Earth at a speed close to the speed of light. Fred, still on Earth, measures the length of the moving spaceship to be about 90 m. At the same time, Joanne (using her own meterstick) measures the length of the spaceship to be

Accepted Answer

A)  about 90 m because of the motion of the spaceship. 
B)  100 m because she is "at rest" on the spaceship. 
C)  It cannot be concluded from the information given. 
D)  about 110 m because both she and the spaceship are moving. 
A)  about 90 m because of the motion of the spaceship. 
B)  100 m because she is "at rest" on the spaceship. 
C)  It cannot be concluded from the information given. 
D)  about 110 m because both she and the spaceship are moving.

Question 16

Which effects have been useful (and successful) in the search for and identification of black holes in the universe?

Accepted Answer

A)  influence of their intense gravitational field on atoms that are emitting light from the event horizons of the black holes 
B)  their gravitational influence on nearby matter, particularly companion stars 
C)  effect of their angular momentum, or spin, on nearby matter 
D)  their magnetic fields and the influence of these fields on nearby matter 
A)  influence of their intense gravitational field on atoms that are emitting light from the event horizons of the black holes 
B)  their gravitational influence on nearby matter, particularly companion stars 
C)  effect of their angular momentum, or spin, on nearby matter 
D)  their magnetic fields and the influence of these fields on nearby matter

Question 17

What happens to the density of an object as it moves with respect to an observer as compared to the same object at rest with respect to the same observer?

Accepted Answer

A)  The density will decrease. 
B)  The density will remain unchanged. 
C)  The density will increase. 
D)  The density can either increase or decrease depending on its direction of motion with respect to the observer. 
A)  The density will decrease. 
B)  The density will remain unchanged. 
C)  The density will increase. 
D)  The density can either increase or decrease depending on its direction of motion with respect to the observer.

Question 18

Some objects in the Milky Way Galaxy are observed to be emitting two oppositely directed jets of material. These gas jets are believed to be

Accepted Answer

A)  energetic, charged particles ejected along the magnetic axes of a rotating white dwarf. 
B)  material squirted out along the rotation axis of an accretion disk around a neutron star or black hole in a binary star system. 
C)  material transferred onto the surface of a white dwarf star in a binary star system, then subsequently blasted into space by runaway thermonuclear fusion reactions. 
D)  material expelled from the far side of the companion star in a binary system, repelled by magnetic interaction with the pulsar. 
A)  energetic, charged particles ejected along the magnetic axes of a rotating white dwarf. 
B)  material squirted out along the rotation axis of an accretion disk around a neutron star or black hole in a binary star system. 
C)  material transferred onto the surface of a white dwarf star in a binary star system, then subsequently blasted into space by runaway thermonuclear fusion reactions. 
D)  material expelled from the far side of the companion star in a binary system, repelled by magnetic interaction with the pulsar.

Question 19

How has the mass of the black hole candidate Cygnus X-1 been estimated?

Accepted Answer

A)  from the periodic wobble it produces in the spectral lines of a normal companion star around which it orbits 
B)  from the gravitational redshift, where the more massive the object, the greater the redshift of its spectral lines 
C)  from the observed size and estimated density of the object 
D)  from the periodic wobble in its own characteristic black-hole spectrum 
A)  from the periodic wobble it produces in the spectral lines of a normal companion star around which it orbits 
B)  from the gravitational redshift, where the more massive the object, the greater the redshift of its spectral lines 
C)  from the observed size and estimated density of the object 
D)  from the periodic wobble in its own characteristic black-hole spectrum

Question 20

The existence of gravitational waves was first suggested observationally by measurements of

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.

What appears to happen to a clock as it approaches and reaches the event horizon around a black hole when viewed by a remote observer?

What is Hawking radiation?

Suppose that a clock is carefully calibrated to tick at a regular rate. If one is brought inside a strong gravitational field, an observer far from that gravitational field would measure the clock to tick

How much energy does a typical longer-living gamma-ray burst emit in 100 seconds?

Supposedly nothing can escape from a black hole, yet astronomers are locating black hole candidates by the X-rays they emit. How can X-rays be coming from a black hole?

Gamma-ray bursts are at great distances from Earth, yet Earth receives tremendous amounts of energy from them. Explain.

An electromagnetic wave leaves the surface of a neutron star and travels outward. As the wave gets farther from the star's surface, the _ and the _.

At which of these locations will Newton's laws of motion be MOST inadequate in describing precisely the motions of objects?

What is a Kerr black hole?

What is a superstring?

What happens to a photon that leaves the interior of a black hole aimed directly upward (radially outward)?

How was the mass of the candidate black hole at the center of the galaxy M87 estimated?

Suppose that a large piece (e.g., 5 solar masses) of purple, magnetized iron is rotating 5 times per day. If this object were able to collapse gravitationally to form a black hole, which of these properties of the matter inside the black hole could an outside observer actually measure?

Light leaving the surface of a neutron star is strongly redshifted. What name is given to this effect?

Which effects have been useful (and successful) in the search for and identification of black holes in the universe?

What happens to the density of an object as it moves with respect to an observer as compared to the same object at rest with respect to the same observer?

Some objects in the Milky Way Galaxy are observed to be emitting two oppositely directed jets of material. These gas jets are believed to be

How has the mass of the black hole candidate Cygnus X-1 been estimated?

The existence of gravitational waves was first suggested observationally by measurements of

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 appears to happen to a clock as it approaches and reaches the event horizon around a black hole when viewed by a remote observer?

What is Hawking radiation?

Suppose that a clock is carefully calibrated to tick at a regular rate. If one is brought inside a strong gravitational field, an observer far from that gravitational field would measure the clock to tick

How much energy does a typical longer-living gamma-ray burst emit in 100 seconds?

Supposedly nothing can escape from a black hole, yet astronomers are locating black hole candidates by the X-rays they emit. How can X-rays be coming from a black hole?

Gamma-ray bursts are at great distances from Earth, yet Earth receives tremendous amounts of energy from them. Explain.

An electromagnetic wave leaves the surface of a neutron star and travels outward. As the wave gets farther from the star's surface, the _____ and the _____.

At which of these locations will Newton's laws of motion be MOST inadequate in describing precisely the motions of objects?

What is a Kerr black hole?

What is a superstring?

What happens to a photon that leaves the interior of a black hole aimed directly upward (radially outward)?

How was the mass of the candidate black hole at the center of the galaxy M87 estimated?

Suppose that a large piece (e.g., 5 solar masses) of purple, magnetized iron is rotating 5 times per day. If this object were able to collapse gravitationally to form a black hole, which of these properties of the matter inside the black hole could an outside observer actually measure?

Light leaving the surface of a neutron star is strongly redshifted. What name is given to this effect?

Which effects have been useful (and successful) in the search for and identification of black holes in the universe?

What happens to the density of an object as it moves with respect to an observer as compared to the same object at rest with respect to the same observer?

Some objects in the Milky Way Galaxy are observed to be emitting two oppositely directed jets of material. These gas jets are believed to be

How has the mass of the black hole candidate Cygnus X-1 been estimated?

The existence of gravitational waves was first suggested observationally by measurements of

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

An electromagnetic wave leaves the surface of a neutron star and travels outward. As the wave gets farther from the star's surface, the _ and the _.