Question 1

The best observational evidence for the existence of black holes is

Accepted Answer

A) Pulsar emission 
B) Massive,mass-transfer X-ray binaries 
C) Evolved red giants with masses in excess of 3 solar masses 
D) Supernova explosions 
E) Planetary nebulae 
A) Pulsar emission 
B) Massive,mass-transfer X-ray binaries 
C) Evolved red giants with masses in excess of 3 solar masses 
D) Supernova explosions 
E) Planetary nebulae

Question 2

The Schwarzschild radius of a 10 solar mass black hole is about 30 km.How large is the Schwarzschild radius of a 5 solar mass black hole?

Accepted Answer

A) 7.5 km 
B) 15 km 
C) 60 km 
D) 120 km 
A) 7.5 km 
B) 15 km 
C) 60 km 
D) 120 km

Question 3

The Crab Nebula is powered by

Accepted Answer

A) Radioactive decay 
B) Release of gravitational potential energy 
C) Rotational kinetic energy of the Crab Nebula pulsar 
D) Nuclear reactions in the center of the nebula 
A) Radioactive decay 
B) Release of gravitational potential energy 
C) Rotational kinetic energy of the Crab Nebula pulsar 
D) Nuclear reactions in the center of the nebula

Question 4

If the Sun were replaced by a black hole having a mass of 1 solar mass,what would happen to the Earth's orbit?

Accepted Answer

A) The Earth would spiral inward 
B) The Earth would jump to a smaller orbit 
C) The size of the Earth's orbit would increase rapidly 
D) The Earth's orbit would remain the same 
A) The Earth would spiral inward 
B) The Earth would jump to a smaller orbit 
C) The size of the Earth's orbit would increase rapidly 
D) The Earth's orbit would remain the same

Question 5

What can escape from within the Schwarzschild radius of a black hole?

Accepted Answer

A) Nothing 
B) Photons 
C) Neutrinos 
D) Antiparticles 
A) Nothing 
B) Photons 
C) Neutrinos 
D) Antiparticles

Question 6

Which of the following is true of a massive neutron star compared to one of smaller mass?

Accepted Answer

A) It is larger and lower in density 
B) It is larger and higher in density 
C) It is smaller and higher in density 
D) It is smaller and lower in density 
A) It is larger and lower in density 
B) It is larger and higher in density 
C) It is smaller and higher in density 
D) It is smaller and lower in density

Question 7

How do we know that pulsars aren't rotating white dwarfs?

Accepted Answer

A) A white dwarf would break up if it rotated as fast as a pulsar 
B) There is only one rate at which white dwarfs can rotate 
C) White dwarf stars can't rotate 
D) There are not enough white dwarfs to account for the number of known pulsars 
A) A white dwarf would break up if it rotated as fast as a pulsar 
B) There is only one rate at which white dwarfs can rotate 
C) White dwarf stars can't rotate 
D) There are not enough white dwarfs to account for the number of known pulsars

Question 8

What kind of pressure supports a white dwarf star?

Accepted Answer

A) Degenerate neutron pressure 
B) Radiation pressure 
C) Normal gas pressure 
D) Degenerate electron pressure 
A) Degenerate neutron pressure 
B) Radiation pressure 
C) Normal gas pressure 
D) Degenerate electron pressure

Question 9

What kind of telescope was used to detect the first known neutron star?

Accepted Answer

A) A radio telescope 
B) An optical telescope 
C) An orbiting ultraviolet telescope 
D) An infrared telescope 
A) A radio telescope 
B) An optical telescope 
C) An orbiting ultraviolet telescope 
D) An infrared telescope

Question 10

Which of the following cannot be determined for the material inside a black hole?

Accepted Answer

A) Mass 
B) Electric charge 
C) Chemical composition 
D) Angular momentum 
A) Mass 
B) Electric charge 
C) Chemical composition 
D) Angular momentum

Question 11

Which of the following is true of the central star of a planetary nebula?

Accepted Answer

A) It is about to become a white dwarf 
B) It is about to produce a supernova outburst 
C) It is a main sequence star 
D) It is a proto-star 
A) It is about to become a white dwarf 
B) It is about to produce a supernova outburst 
C) It is a main sequence star 
D) It is a proto-star

Question 12

Approximately how massive must a black hole be in order to be as large as the Earth (6000 km in radius)?

Accepted Answer

A) A few hundredths of a solar mass 
B) A few solar masses 
C) A few tens of solar masses 
D) A few thousand solar masses 
A) A few hundredths of a solar mass 
B) A few solar masses 
C) A few tens of solar masses 
D) A few thousand solar masses

Question 13

What fraction of the white dwarfs have masses greater than 8 times the mass of the Sun?

Accepted Answer

A) Nearly 100% 
B) About 1 in a 100 
C) About 1 in 10 
D) None have masses that large 
A) Nearly 100% 
B) About 1 in a 100 
C) About 1 in 10 
D) None have masses that large

Question 14

How do we know that gamma ray bursts occur at very great distances?

Accepted Answer

A) They occur in highly redshifted galaxies 
B) They are all too faint to be nearby 
C) They are confined to the plane of the Milky Way 
D) They show no parallax 
A) They occur in highly redshifted galaxies 
B) They are all too faint to be nearby 
C) They are confined to the plane of the Milky Way 
D) They show no parallax

Question 15

If the unseen component of a binary star has a mass greater than about 3 solar masses,theory tells that it must be what kind of object?

Accepted Answer

A) A black hole. 
B) A neutron star. 
C) A red giant. 
D) A white dwarf. 
A) A black hole. 
B) A neutron star. 
C) A red giant. 
D) A white dwarf.

Question 16

The term "event horizon" refers to which of the following?

Accepted Answer

A) The depth to which we can see into the Sun 
B) The surface of a black hole 
C) The greatest distance to which we can see with current telescopes 
D) The obscuration of starlight by interstellar dust 
A) The depth to which we can see into the Sun 
B) The surface of a black hole 
C) The greatest distance to which we can see with current telescopes 
D) The obscuration of starlight by interstellar dust

Question 17

Which of the following is an essential part of Einstein's explanation of gravity?

Accepted Answer

A) Matter causes curvature of space 
B) The gravity of a moving object varies with time 
C) Gravitational forces exist only over a limited distance 
D) Anti-matter has negative gravity 
A) Matter causes curvature of space 
B) The gravity of a moving object varies with time 
C) Gravitational forces exist only over a limited distance 
D) Anti-matter has negative gravity

Question 18

What type of star is supported by the pressure produced by its degenerate electrons?

Accepted Answer

A) A white dwarf 
B) A neutron star 
C) A main sequence star 
D) A pulsar 
A) A white dwarf 
B) A neutron star 
C) A main sequence star 
D) A pulsar

Question 19

A white dwarf star has the same mass as the Sun but a radius 1/100 that of the Sun.How does the surface gravity of the white dwarf compare with that of the Sun?

Accepted Answer

A) 1/100 as large 
B) The same 
C) 100 times as large 
D) 10,000 times as large 
A) 1/100 as large 
B) The same 
C) 100 times as large 
D) 10,000 times as large

Question 20

As a star collapses to produce a black hole,the photons that escape from it

Accepted Answer

A) Move faster than the speed of light 
B) Are redshifted 
C) Turn into neutrinos 
D) Produce a white hole 
A) Move faster than the speed of light 
B) Are redshifted 
C) Turn into neutrinos 
D) Produce a white hole

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

The best observational evidence for the existence of black holes is

The Schwarzschild radius of a 10 solar mass black hole is about 30 km.How large is the Schwarzschild radius of a 5 solar mass black hole?

The Crab Nebula is powered by

If the Sun were replaced by a black hole having a mass of 1 solar mass,what would happen to the Earth's orbit?

What can escape from within the Schwarzschild radius of a black hole?

Which of the following is true of a massive neutron star compared to one of smaller mass?

How do we know that pulsars aren't rotating white dwarfs?

What kind of pressure supports a white dwarf star?

What kind of telescope was used to detect the first known neutron star?

Which of the following cannot be determined for the material inside a black hole?

Which of the following is true of the central star of a planetary nebula?

Approximately how massive must a black hole be in order to be as large as the Earth (6000 km in radius)?

What fraction of the white dwarfs have masses greater than 8 times the mass of the Sun?

How do we know that gamma ray bursts occur at very great distances?

If the unseen component of a binary star has a mass greater than about 3 solar masses,theory tells that it must be what kind of object?

The term "event horizon" refers to which of the following?

Which of the following is an essential part of Einstein's explanation of gravity?

What type of star is supported by the pressure produced by its degenerate electrons?

A white dwarf star has the same mass as the Sun but a radius 1/100 that of the Sun.How does the surface gravity of the white dwarf compare with that of the Sun?

As a star collapses to produce a black hole,the photons that escape from it

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