Question 1

Could our Sun ever undergo a nova or a white-dwarf supernova event? Why or why not?

Accepted Answer

No, because both events can on...

Question 2

If you had something the size of a sugar cube that was made of neutron star matter, it would weigh ________.

Accepted Answer

A)   about as much as a large mountain
B)   about 50 pounds
C)   as much as the entire Earth
D)   about as much as a truckE) All of the above
F) A) and C)

Question 3

From an observational standpoint, what is a pulsar?

Accepted Answer

A)   A star that slowly changes its brightness, getting dimmer and then brighter, with a period of anywhere from a few hours to a few weeks.
B)   An object that emits flashes of light several times per second (or even faster) , with near perfect regularity.
C)   An object that emits random "pulses" of light, sometimes with only a fraction of a second between pulses and other times with several days between pulses.
D)   A star that changes color rapidly, from blue to red and back again.E) A) and B)
F) C) and D)

Question 4

Order the following objects in increasing size (radius) :

Accepted Answer

A)   Jupiter, white dwarf, neutron star, Sun
B)   neutron star, white dwarf, Jupiter, Sun
C)   Jupiter, white dwarf, Sun, neutron star
D)   neutron star, Jupiter, white dwarf, SunE) All of the above
F) A) and D)

Question 5

What causes the radio pulses of a pulsar?

Accepted Answer

A)   The vibration of the neutron star.
B)   As the neutron star spins, beams of radio radiation sweep through space. If one of the beams crosses the Earth, we observe a pulse.
C)   The neutron star undergoes periodic explosions of nuclear fusion that generate radio pulses.
D)   The neutron star's orbiting companion periodically eclipses the radio waves that the neutron star emits.
E)   A black hole near the neutron star absorbs energy and re-emits it as radio waves.F) None of the above
G) A) and B)

Question 6

What is the evidence that gamma-ray bursts originate from beyond the Milky Way Galaxy?

Accepted Answer

Gamma-ray bursts are distributed uniform...

Question 7

Which statement about pulsars is not thought to be true?

Accepted Answer

A)   Pulsars can form only in close binary systems.
B)   All pulsars are neutron stars, but not all neutron stars are pulsars.
C)   A pulsar must have a very strong magnetic field and rotate quite rapidly.
D)   Pulsars are kept from collapsing by neutron degeneracy pressure.E) B) and C)
F) A) and D)

Question 8

Based on current evidence, which of the following statements about gamma ray bursts is true?

Accepted Answer

A)   All those that we have detected occurred in distant galaxies.
B)   They come primarily from the Milky Way's central black hole.
C)   They occur in the same types of close binary systems that produce X-ray bursts.
D)   All gamma ray bursts are produced by supernovae.E) None of the above
F) B) and D)

Question 9

Light escaping from white dwarfs will show a gravitational redshift.

Accepted Answer

A) True 
 B)False

Question 10

From a theoretical standpoint, what is a pulsar?

Accepted Answer

A)   a star that alternately expands and contracts in size
B)   a rapidly rotating neutron star
C)   a neutron star or black hole that happens to be in a binary system
D)   a binary system that happens to be aligned so that one star periodically eclipses the other
E)   a star that is burning iron in its coreF) None of the above
G) A) and B)

Question 11

What is an accretion disk?

Accepted Answer

A)   A disk of hot gas swirling rapidly around a white dwarf, neutron star, or black hole
B)   Any flattened disk in space, such as the disk of the Milky Way Galaxy
C)   A stream of gas flowing from one star to its binary companion star
D)   A disk of material found around every white dwarf in the Milky Way GalaxyE) C) and D)
F) A) and C)

Question 12

Which statement about accretion disks is not true?

Accepted Answer

A)   The primary factor determining whether a white dwarf has an accretion disk is the white dwarf's mass.
B)   The gas in the inner parts of the disk travels faster than the gas in the outer parts of the disk.
C)   The gas in the inner parts of the disk is hotter than the gas in the outer parts of the disk.
D)   Accretion disks are made primarily of hydrogen and helium gas.E) A) and B)
F) B) and D)

Question 13

There is no upper limit to the mass of a neutron star.

Accepted Answer

A) True 
 B)False

Question 14

What makes us think that the star system Cygnus X-1 contains a black hole?

Accepted Answer

A)   It emits X-rays characteristic of an accretion disk, but the unseen star in the system is too massive to be a neutron star.
B)   No light is emitted from this star system, so it must contain a black hole.
C)   The fact that we see strong X-ray emission tells us that the system must contain a black hole.
D)   Cygnus X-1 is a powerful X-ray burster, so it must contain a black hole.E) C) and D)
F) A) and B)

Question 15

A teaspoonful of white dwarf material on Earth would weigh

Accepted Answer

A)   a few grams.
B)   a few pounds.
C)   a few tons.
D)   about the same as Mt. Everest.
E)   about the same as the Earth.F) A) and B)
G) B) and C)

Question 16

A white dwarf supernova event is very important to calibrating Hubble's Law. Why? Choose the best answer for the question.

Accepted Answer

A)   It can only happen to white dwarfs.
B)   It is a very rare event.
C)   It is a very luminous standard candle.
D)   The white dwarf supernova in a galaxy tells us how fast a galaxy is expanding away from us.E) None of the above
F) B) and C)

Question 17

Suppose you drop a clock toward a black hole. As you look at the clock from a high orbit, what will you notice?

Accepted Answer

A)   Time on the clock will run slower as it approaches the black hole, and light from the clock will be increasingly redshifted.
B)   Time on the clock will run faster as it approaches the black hole, and light from the clock will be increasingly blueshifted.
C)   The clock will fall toward the black hole at a steady rate, so that you'll see it plunge through the event horizon within just a few minutes.
D)   The clock will fall faster and faster, reaching the speed of light as it crosses the event horizon.E) B) and D)
F) All of the above

Question 18

Suppose you find an X-ray binary system that shows X-ray bursts. Is it possible that this system consists of a red giant and a black hole? Why or why not?

Accepted Answer

No. X-ray bursts occur when ac...

Question 19

Which of the following statements about electron degeneracy pressure and neutron degeneracy pressure is true?

Accepted Answer

A)   Electron degeneracy pressure is the main source of pressure in white dwarfs, while neutron degeneracy pressure is the main source of pressure in neutron stars.
B)   Both electron degeneracy pressure and neutron degeneracy pressure help govern the internal structure of a main-sequence star.
C)   The life of a white dwarf is an ongoing battle between electron degeneracy pressure and neutron degeneracy pressure.
D)   In a black hole, the pressure coming from neutron degeneracy pressure is slightly greater than that coming from electron degeneracy pressure.E) A) and B)
F) C) and D)

Question 20

Briefly describe what you would see if your friend plunged into a black hole.

Accepted Answer

As he approached the black hole, he woul...

Exam 13: Bizarre Stellar Graveyard

Order the following objects in increasing size (radius) :

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Suppose you drop a clock toward a black hole. As you look at the clock from a high orbit, what will you notice?

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Light escaping from white dwarfs will show a gravitational redshift.

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What is an accretion disk?

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Briefly describe what you would see if your friend plunged into a black hole.

Correct AnswerverifiedAs he approached the black hole, he woul...View AnswerShow Answer

Which statement about pulsars is not thought to be true?

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Suppose you find an X-ray binary system that shows X-ray bursts. Is it possible that this system consists of a red giant and a black hole? Why or why not?

Correct AnswerverifiedNo. X-ray bursts occur when ac...View AnswerShow Answer

A white dwarf supernova event is very important to calibrating Hubble's Law. Why? Choose the best answer for the question.

Correct AnswerverifiedShow Answer

Based on current evidence, which of the following statements about gamma ray bursts is true?

Correct AnswerverifiedShow Answer

Which of the following statements about electron degeneracy pressure and neutron degeneracy pressure is true?

Correct AnswerverifiedShow Answer

Could our Sun ever undergo a nova or a white-dwarf supernova event? Why or why not?

Correct AnswerverifiedNo, because both events can on...View AnswerShow Answer

A teaspoonful of white dwarf material on Earth would weigh

Correct AnswerverifiedShow Answer

What is the evidence that gamma-ray bursts originate from beyond the Milky Way Galaxy?

Correct AnswerverifiedGamma-ray bursts are distributed uniform...View AnswerShow Answer

Which statement about accretion disks is not true?

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What causes the radio pulses of a pulsar?

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What makes us think that the star system Cygnus X-1 contains a black hole?

Correct AnswerverifiedShow Answer

From an observational standpoint, what is a pulsar?

Correct AnswerverifiedShow Answer

There is no upper limit to the mass of a neutron star.

Correct AnswerverifiedShow Answer

If you had something the size of a sugar cube that was made of neutron star matter, it would weigh ________.

Correct AnswerverifiedShow Answer

From a theoretical standpoint, what is a pulsar?

Correct AnswerverifiedShow Answer

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As he approached the black hole, he woul...
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No. X-ray bursts occur when ac...
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No, because both events can on...
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Gamma-ray bursts are distributed uniform...
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