Question 1

As time progresses,the pulse rate for most solitary pulsars:

Accepted Answer

A)   varies periodically as the neutron star undergoes periodic expansions and contractions.
B)   slows down since rotational energy is being used to generate the pulses.
C)   speeds up as the neutron star slowly contracts under gravity.
D)   remains absolutely constant; pulsars provide ideal frequency standards, or clocks.E) A) and B)
F) C) and D)

Question 2

If a person falls as far as the event horizon of a black hole,what would happen to the person's heart rate (apart from the effects caused by the person's adrenaline level) ?

Accepted Answer

A)   The heart rate would appear to have slowed down somewhat, but not much, because of the change of the speed of light in the gravity field.
B)   The heart rate would appear to be zero; his heart would appear to have stopped.
C)   The heart rate would appear to have speeded up to an incredible rate.
D)   The heart rate would appear to be normal since gravity has no effect on time intervals.E) B) and C)
F) All of the above

Question 3

The last supernova in our Galaxy that was visible to the naked eye was observed when?

Accepted Answer

A)   We have never seen a naked-eye supernova.
B)   They are quite common, so we undoubtedly saw one within the last year.
C)   There are reports of a supernova eruption in 1066.
D)   Kepler observed a naked-eye supernova in 1604. This was the most recent one.E) None of the above
F) B) and C)

Question 4

In 2014,astronomers discovered the millisecond pulsar PSR J0337+1715 in the constellation Taurus.What is so significant about this discovery?

Accepted Answer

A)   It is a neutron star with a mass more than a thousand times the mass of the Sun.
B)   It is the result of two neutron stars that collided with each other.
C)   It is a pulsar that was not precessing and, in fact, that aimed its radiation beam directly at Earth.
D)   The pulsar is in an orbiting system with two white dwarfs.E) A) and B)
F) B) and C)

Question 5

What causes a glitch in the rotation rate of a pulsar?

Accepted Answer

A)   Hot spots develop on the surface of a neutron star, and from these spots, jets of material can suddenly shoot out causing a minor but abrupt chance in the rotation rate.
B)   Because of their enormous density, the rotation rates of neutron stars are quantized and must change abruptly from one rotation rate to another.
C)   As the star slows, its shape becomes more spherical. If its rotation rate adjusts to this suddenly, a glitch occurs.
D)   When a pulsar occurs in a binary system, the binary companion can send clumps of material to land on its surface. This will change its rotation rate abruptly.E) A) and C)
F) None of the above

Question 6

The 2004 discovery of two pulsars in orbit around their common center of mass is significant because it gives a unique opportunity to study some of the predictions of:

Accepted Answer

A)   Kepler's laws.
B)   the theory of angular momentum.
C)   general relativity.
D)   Wein's displacement law.E) B) and D)
F) A) and C)

Question 7

Because of the relativistic nature of spacetime in the vicinity of a black hole,a satellite orbiting the hole in one direction would have a different orbital period from a satellite orbiting in the other direction.This fact is a violation of:

Accepted Answer

A)   the conservation of energy.
B)   the principle of equivalence.
C)   Kepler's third law.
D)   the conservation of angular momentum.E) B) and D)
F) A) and D)

Question 8

Suppose you are in a jet airliner traveling at a constant speed of 400 km/h in a constant direction.All windows are blocked,so you cannot see outside,and there are no vibrations from the engines.What experiment can you do to determine that you are in fact moving?

Accepted Answer

A)   Suspend a ball by a thread from the ceiling and measure the angle the thread makes with the vertical.
B)   None-all experiments will give the same results that you would get when at rest on the ground.
C)   Measure the speed of a sound wave traveling up the aisle (toward the nose of the aircraft)  and another traveling down toward the tail, and calculate the difference between the two results.
D)   Drop a small rock and measure the distance it moves backward down the aisle as it falls.E) A) and B)
F) A) and D)

Question 9

What is the origin of the rings of gas that surround Supernova 1987A?

Accepted Answer

A)   The rings were formed by stellar winds before the supernova erupted.
B)   These were caused by the gamma rays, which also caused photodisintegration.
C)   These rings were pushed out by the core bounce.
D)   The rings were formed when the shock wave lifted the outer layers of the star.E) None of the above
F) A) and B)

Question 10

The main reason for the observed slowdown of many pulsars is:

Accepted Answer

A)   friction between the stellar surface and the surrounding nebular material.
B)   a slow buildup of the magnetic field; rotational energy is transferred to magnetic energy.
C)   the loss of rotational energy to provide energy for the emission of radiation.
D)   the slowing of rotation caused by slow expansion and redistribution of mass of the source, similar to the slowdown of a spinning skater.E) B) and D)
F) B) and C)

Question 11

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 holeE) A) and C)
F) B) and C)

Question 12

When a typical nova explodes,it brightens in a few hours by a factor of:

Accepted Answer

A)   10⁸ to 10¹⁰.
B)   2 to 5.
C)   10⁴ to 10⁶.
D)   10 to 100.E) B) and C)
F) A) and D)

Question 13

Each successive stage of core nuclear reactions in a massive star lasts for considerably less time than the previous stage (e.g.,for a 25-solar-mass star,carbon fusion lasts for 600 years,while neon fusion lasts for only 1 year) .One reason is that the:

Accepted Answer

A)   later the stage of fusion, the less massive is the star.
B)   later the stage of fusion, the more massive is the star.
C)   more massive the nuclei, the fewer there are to react together.
D)   more massive the nuclei, the less energy is released by fusing them together.E) B) and D)
F) A) and B)

Question 14

Particularly powerful supernovae called hypernovae occur in:

Accepted Answer

A)   supermassive black holes.
B)   neutron stars.
C)   Wolf-Rayet stars.
D)   hyperspace.E) All of the above
F) C) and D)

Question 15

Which technique 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 imagesE) None of the above
F) A) and D)

Question 16

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.E) A) and B)
F) None of the above

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.E) None of the above
F) C) and D)

Question 18

The formation of black holes:

Accepted Answer

A)   occurred only during the Big Bang.
B)   was confined to the early era that saw the formation of galaxies.
C)   occurred at the instant dark energy became dominant in the universe.
D)   is ongoing.E) B) and C)
F) All of the above

Question 19

The sequence of thermonuclear fusion processes inside massive stars can transform elements such as carbon and oxygen into heavier elements and generate excess energy until iron has been produced.Why is it NOT possible for fusion reactions to release energy from iron nuclei?

Accepted Answer

A)   The electrostatic charge of iron nuclei is so great that other nuclei cannot approach closely enough to react with them.
B)   Iron has the largest nucleus of all elements, and fusing other nuclei with iron actually reduces the size of the nucleus.
C)   Iron is the heaviest naturally occurring element.
D)   The protons and neutrons in an iron nucleus are so tightly bound together that fusing other nuclei with iron absorbs energy rather than releasing it.E) None of the above
F) B) and D)

Question 20

If you see an object moving past you at 90% of the speed of light,what will its length appear to be?

Accepted Answer

A)   The object will look longer than if it were at rest.
B)   The object will look shorter than if it were at rest.
C)   The object will look shorter than if it were at rest while it is coming toward you and longer after it has passed you.
D)   The length of the object will appear to be unchanged from when it is at rest since it is a solid object.E) None of the above
F) A) and D)

Exam 12: The Deaths and Remnants of Stars

Because of the relativistic nature of spacetime in the vicinity of a black hole,a satellite orbiting the hole in one direction would have a different orbital period from a satellite orbiting in the other direction.This fact is a violation of:

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

When a typical nova explodes,it brightens in a few hours by a factor of:

Correct AnswerverifiedShow Answer

Suppose you are in a jet airliner traveling at a constant speed of 400 km/h in a constant direction.All windows are blocked,so you cannot see outside,and there are no vibrations from the engines.What experiment can you do to determine that you are in fact moving?

Correct AnswerverifiedShow Answer

What is Hawking radiation?

Correct AnswerverifiedShow Answer

What causes a glitch in the rotation rate of a pulsar?

Correct AnswerverifiedShow Answer

As time progresses,the pulse rate for most solitary pulsars:

Correct AnswerverifiedShow Answer

The main reason for the observed slowdown of many pulsars is:

Correct AnswerverifiedShow Answer

The formation of black holes:

Correct AnswerverifiedShow Answer

Each successive stage of core nuclear reactions in a massive star lasts for considerably less time than the previous stage (e.g.,for a 25-solar-mass star,carbon fusion lasts for 600 years,while neon fusion lasts for only 1 year) .One reason is that the:

Correct AnswerverifiedShow Answer

Particularly powerful supernovae called hypernovae occur in:

Correct AnswerverifiedShow Answer

The last supernova in our Galaxy that was visible to the naked eye was observed when?

Correct AnswerverifiedShow Answer

If a person falls as far as the event horizon of a black hole,what would happen to the person's heart rate (apart from the effects caused by the person's adrenaline level) ?

Correct AnswerverifiedShow Answer

The 2004 discovery of two pulsars in orbit around their common center of mass is significant because it gives a unique opportunity to study some of the predictions of:

Correct AnswerverifiedShow Answer

In 2014,astronomers discovered the millisecond pulsar PSR J0337+1715 in the constellation Taurus.What is so significant about this discovery?

Correct AnswerverifiedShow Answer

The sequence of thermonuclear fusion processes inside massive stars can transform elements such as carbon and oxygen into heavier elements and generate excess energy until iron has been produced.Why is it NOT possible for fusion reactions to release energy from iron nuclei?

Correct AnswerverifiedShow Answer

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?

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

What is the origin of the rings of gas that surround Supernova 1987A?

Correct AnswerverifiedShow Answer

If you see an object moving past you at 90% of the speed of light,what will its length appear to be?

Correct AnswerverifiedShow Answer

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