Question 1

Which of the following objects can rotate a thousand times per second without being torn apart?

Accepted Answer

A) White dwarf 
B) Main sequence star 
C) Red giant 
D) Neutron star 
A) White dwarf 
B) Main sequence star 
C) Red giant 
D) Neutron star D

Question 2

Which of the following is true for white dwarf stars?

Accepted Answer

A) They have small radii and large densities 
B) They have large radii and small densities 
C) They have high luminosities and large radii 
D) They have small masses and high luminosities 
A) They have small radii and large densities 
B) They have large radii and small densities 
C) They have high luminosities and large radii 
D) They have small masses and high luminosities A

Question 3

A pulsar spins rapidly because it

Accepted Answer

A) Conserved angular momentum when it shrank 
B) Has been struck a glancing blow by another star 
C) Has formed from a very rapidly rotating gas cloud 
D) Has been accelerated by explosions on its surface 
A) Conserved angular momentum when it shrank 
B) Has been struck a glancing blow by another star 
C) Has formed from a very rapidly rotating gas cloud 
D) Has been accelerated by explosions on its surface A

Question 4

A typical pulsar rotates once per

Accepted Answer

A) Year 
B) Day 
C) Hour 
D) Second 
A) Year 
B) Day 
C) Hour 
D) Second

Question 5

What happens to the escape velocity of an object when it collapses to a size equal to its Schwarzschild radius?

Accepted Answer

A) It goes to zero 
B) It becomes infinite 
C) It becomes negative 
D) It becomes equal to the speed of light 
A) It goes to zero 
B) It becomes infinite 
C) It becomes negative 
D) It becomes equal to the speed of light

Question 6

If we could see the last few seconds of the collapse of a star to form a black hole,we would see the star grow steadily redder.Why?

Accepted Answer

A) The star moves away from us at an increasing speed 
B) The star grows steadily cooler 
C) The star's gravitational redshift increases 
D) The star becomes obscured by more and more interstellar dust 
A) The star moves away from us at an increasing speed 
B) The star grows steadily cooler 
C) The star's gravitational redshift increases 
D) The star becomes obscured by more and more interstellar dust

Question 7

What produces the energy that is released in a Type II supernova explosion (of which SN 1987A was an example)?

Accepted Answer

A) Gravitational collapse 
B) Very rapid consumption of hydrogen 
C) The collision between two stars 
D) The impact of an antimatter asteroid on a star 
A) Gravitational collapse 
B) Very rapid consumption of hydrogen 
C) The collision between two stars 
D) The impact of an antimatter asteroid on a star

Question 8

The approximate size of a white dwarf is

Accepted Answer

A) 10 km 
B) The size of the Earth 
C) The size of the Sun 
D) Between 1.4 and 2.5 solar radii 
A) 10 km 
B) The size of the Earth 
C) The size of the Sun 
D) Between 1.4 and 2.5 solar radii

Question 9

The Chandrasekhar limit is the largest mass that a white dwarf star can have.About how large is the Chandrasekhar limit?

Accepted Answer

A) 1 solar mass 
B) 1.4 solar masses 
C) 2.5 solar masses 
D) 5.2 solar masses 
A) 1 solar mass 
B) 1.4 solar masses 
C) 2.5 solar masses 
D) 5.2 solar masses

Question 10

Which of the following is true of neutron stars?

Accepted Answer

A) Many of them rotate faster than once per second 
B) They are about as large as the Moon 
C) They have small magnetic fields 
D) They eventually become supernovas. 
A) Many of them rotate faster than once per second 
B) They are about as large as the Moon 
C) They have small magnetic fields 
D) They eventually become supernovas.

Question 11

Which of the following best describes how the appearance of a star changes as it evolves after becoming a white dwarf?

Accepted Answer

A) It becomes hotter and brighter 
B) It becomes hotter and dimmer 
C) It becomes cooler and dimmer 
D) It becomes cooler and brighter 
A) It becomes hotter and brighter 
B) It becomes hotter and dimmer 
C) It becomes cooler and dimmer 
D) It becomes cooler and brighter

Question 12

A white dwarf star such as Sirius-B balances the inward gravitational force by

Accepted Answer

A) Radiation pressure 
B) Degenerate electron gas pressure 
C) Degenerate neutron gas pressure 
D) Gas pressure from heat derived from fusion 
E) Energy from recurrent novae 
A) Radiation pressure 
B) Degenerate electron gas pressure 
C) Degenerate neutron gas pressure 
D) Gas pressure from heat derived from fusion 
E) Energy from recurrent novae

Question 13

Electrons moving in a magnetic field produce radiation by the process of

Accepted Answer

A) Synchrotron radiation 
B) Black body emission 
C) Bright line emission 
D) Electron scattering 
A) Synchrotron radiation 
B) Black body emission 
C) Bright line emission 
D) Electron scattering

Question 14

Suppose an astronaut travels close to a black hole's event horizon (but is smart enough not to enter!).If he remains 1 day by his clocks,when he returns to base,he will be

Accepted Answer

A) 1 day older 
B) More than 1 day older 
C) Less than 1 day older 
D) 1 day younger 
A) 1 day older 
B) More than 1 day older 
C) Less than 1 day older 
D) 1 day younger

Question 15

Suppose you were inside the Schwarzschild radius of a black hole.If you were to shine a blue flashlight to a companion exterior to the black hole,he/she would see

Accepted Answer

A) Red light 
B) Blue light 
C) Violet light 
D) No light (can't escape) 
E) White light 
A) Red light 
B) Blue light 
C) Violet light 
D) No light (can't escape) 
E) White light

Question 16

Why are there no white dwarf stars that can be seen with the unaided eye?

Accepted Answer

A) The nearest white dwarf is thousands of parsecs away 
B) White dwarfs are very small in size 
C) Even the hottest white dwarf is very cool 
D) White dwarf stars are surrounded by thick dust shells 
A) The nearest white dwarf is thousands of parsecs away 
B) White dwarfs are very small in size 
C) Even the hottest white dwarf is very cool 
D) White dwarf stars are surrounded by thick dust shells

Question 17

The bright star seen by Chinese astronomers during daylight in the year 1054 AD was (not counting the Sun!)

Accepted Answer

A) The first appearance of Comet Halley 
B) The Crab supernova 
C) The formation of a massive black hole in the galactic center 
D) Alpha Centauri reaching the main sequence 
E) A helium flash on Sirius 
A) The first appearance of Comet Halley 
B) The Crab supernova 
C) The formation of a massive black hole in the galactic center 
D) Alpha Centauri reaching the main sequence 
E) A helium flash on Sirius

Question 18

Pulsars were first discovered

Accepted Answer

A) While studying radio scintillations in the solar wind 
B) While studying rapidly variable stars 
C) In globular clusters 
D) In a search for 21 cm radiation from other galaxies. 
A) While studying radio scintillations in the solar wind 
B) While studying rapidly variable stars 
C) In globular clusters 
D) In a search for 21 cm radiation from other galaxies.

Question 19

Which of the following best describes the relationship between mass and radius for white dwarf stars?

Accepted Answer

A) Radius is independent of mass 
B) More massive white dwarfs are larger 
C) More massive white dwarfs are smaller 
D) All white dwarfs have the same size 
A) Radius is independent of mass 
B) More massive white dwarfs are larger 
C) More massive white dwarfs are smaller 
D) All white dwarfs have the same size

Question 20

The size of a black hole is entirely determined by which of the following?

Accepted Answer

A) Mass 
B) Chemical composition 
C) Age 
D) Rate of accretion of new material 
A) Mass 
B) Chemical composition 
C) Age 
D) Rate of accretion of new material

Exam 20: White Dwarfs, neutron Stars, and Black Holes

Which of the following objects can rotate a thousand times per second without being torn apart?

Which of the following is true for white dwarf stars?

A pulsar spins rapidly because it

A typical pulsar rotates once per

What happens to the escape velocity of an object when it collapses to a size equal to its Schwarzschild radius?

If we could see the last few seconds of the collapse of a star to form a black hole,we would see the star grow steadily redder.Why?

What produces the energy that is released in a Type II supernova explosion (of which SN 1987A was an example)?

The approximate size of a white dwarf is

The Chandrasekhar limit is the largest mass that a white dwarf star can have.About how large is the Chandrasekhar limit?

Which of the following is true of neutron stars?

Which of the following best describes how the appearance of a star changes as it evolves after becoming a white dwarf?

A white dwarf star such as Sirius-B balances the inward gravitational force by

Electrons moving in a magnetic field produce radiation by the process of

Suppose an astronaut travels close to a black hole's event horizon (but is smart enough not to enter!).If he remains 1 day by his clocks,when he returns to base,he will be

Suppose you were inside the Schwarzschild radius of a black hole.If you were to shine a blue flashlight to a companion exterior to the black hole,he/she would see

Why are there no white dwarf stars that can be seen with the unaided eye?

The bright star seen by Chinese astronomers during daylight in the year 1054 AD was (not counting the Sun!)

Pulsars were first discovered

Which of the following best describes the relationship between mass and radius for white dwarf stars?

The size of a black hole is entirely determined by which of the following?

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