Deck 11: Neutron Stars and Black Holes

Question 1

An isolated black hole in empty intergalactic space would be difficult to detect because

A) there would be no stars behind it whose light would be affected by gravitational lensing.
B) it could not emit light from inside its event horizon.
C) no companion stars would be affected by its gravitational field.
D) no matter would be falling into it to create an X-ray-emitting accretion disk.
E) All of the other choices are correct.

Answer 1

E

Question 2

___ _____ _ occurs when light travels out of a gravitational field, loses energy, and its wavelength grows longer.

A) A gravitational blue shift
B) The solar wind
C) A gravitational redshift
D) A X-ray burst
E) A pulsar wind

Answer 2

C

Question 3

The slowing of clocks in strongly curved space time is known as

A) gravitational radiation.
B) time dilation.
C) gravitational curvature.
D) gravitational redshift.
E) hyperspace drag.

Answer 3

B

Question 4

The event horizon

A) is believed to be a singularity.
B) is a crystalline layer.
C) has a radius equal to the Schwarzschild radius.
D) marks the inner boundary of a planetary nebula.
E) is located at the point where synchrotron radiation is created around a pulsar.

Question 5

The ___ _______ _ of a black hole is the radius from a black hole at which the escape velocity is approximately equal to the speed of light.

A) Roche limit
B) Lagrangian point
C) Chandraskhar limit
D) Hubble radius
E) event horizon

Question 6

Although neutron stars are very hot, they are faint and not easy to see at visual wavelengths because

A) light does not escape from their event horizon.
B) most lie beyond dense dust clouds.
C) they have only a small surface area from which to emit.
D) the peak of their thermal emission is at much shorter wavelengths than visual.
E) they have only a small surface area from which to emit and the peak of their thermal emission is at much shorter wavelengths than visual.

Question 7

The density of a neutron star is

A) about the same as that of a white dwarf.
B) about the same as that of the Sun.
C) about the same as an atomic nucleus.
D) zero.

Question 8

The density of a __ _____ __ is greater than the density of a __ _____ __.

A) white dwarf; neutron star
B) neutron star; black hole
C) pulsar; neutron star
D) pulsar; white dwarf
E) white dwarf; black hole

Question 9

Which of the following objects is considered to possibly contain a black hole?

A) the central star of the Crab nebula
B) the Orion nebula.
C) LMC X-3
D) Algol
E) PSR 1257+12

Question 10

___ _____ _ are neutron stars that have magnetic fields 100 times stronger than the average neutron star.

A) Hypernovae
B) Collapsars
C) Pulsars
D) Kerr singularities
E) Magnetars

Question 11

Hypernovae are

A) supernovae that occur when two red dwarfs collide.
B) supernovae that occur when 10-solar-mass stars explode.
C) supernovae that occur when stars more massive than 25 solar masses explode.
D) one theory to explain the production of gamma-ray bursters.
E) supernovae that occur when stars more massive than 25 solar masses explode and one theory to explain the production of gamma-ray bursters.

Question 12

Cygnus X-1 and LMC X-3 are black holes if the masses of the unseen companions perhaps may be

A) less than 3 solar masses.
B) more than 3 solar masses.
C) between 0.4 and 1.4 solar masses.
D) less than 0.4 solar masses.
E) not larger than the masses of the stars that we can see.

Question 13

Observations from the Compton Gamma Ray Observatory showed that gamma-ray bursters were located throughout the sky. This told us that

A) the bursts were not produced among stars in the disk of our galaxy.
B) the bursts were not produced among stars in the nuclear bulge of our galaxy.
C) the bursts are not associated with planets in our solar system.
D) the bursts were not produced in our Sun.
E) All of the other choices are correct.

Question 14

Pulsars cannot be spinning white dwarfs because

A) white dwarfs are not that common.
B) white dwarfs are not dense enough.
C) white dwarfs do not have magnetic fields.
D) a white dwarf spinning that fast would fly apart.
E) All of the other choices are correct.

Question 15

Neutron stars are expected to spin rapidly because

A) they conserved angular momentum when they collapsed.
B) they have high orbital velocities.
C) they have high densities.
D) they have high temperatures.
E) the energy from the supernova explosion that formed them made them spin faster.

Question 16

The size of a neutron star is

A) about the same as that of our Solar System.
B) about the same as that of the Sun.
C) about the same as Earth.
D) smaller than any of these.

Question 17

The peculiar system SS 433
I) is emitting beams of energy and matter.
II) is producing a spectrum with both a red and a blue shift.
III) probably contains an accretion disk.
IV) is the result of a planetary nebula.

A) I
B) III
C) II & III
D) I, II, & III
E) I, II, III, & IV

Question 18

A __ _____ __ has a radius of about 10 km and is supported by the pressure associated with degenerate neutrons.

A) black hole
B) neutron star
C) white dwarf
D) supernova remnant
E) red dwarf

Question 19

Similar to our Sun, pulsars' rotations are believed to slow down because

A) they are losing angular momentum into space via outward streaming particles.
B) they are dragging companion stars around in their magnetic field.
C) they are getting tired.
D) of conservation of angular momentum.
E) their mass is increasing.

Question 20

The mass of a neutron star is

A) several time that of the Sun.
B) about the same as that of the Sun.
C) about the same as Earth.
D) smaller than any of these.

Question 21

For a point mass equal to that of the Sun, how far does the Schwarzschild radius extend from its center?

A) A few kilometers away
B) A few solar radii away
C) A few astronomical units (AU) away
D) A few parsecs away

Question 22

A pulsar requires that a neutron star
I) rotate rapidly.
II) have a radius of at least 10 km.
III) have a strong magnetic field.
IV) rotate on an axis that is different from the axis of the magnetic field.

A) I & III
B) I & IV
C) II, III, & IV
D) I, III, & IV
E) I, II, III, & IV

Question 23

The first pulsar was discovered by _ _____ ___ in November of 1967.

A) Jocelyn Bell
B) Isaac Newton
C) Albert Einstein
D) Walter Baade
E) Edwin Hubble

Question 24

The calculated Schwarzschild radius of a 2- black hole is approximately

A) 6 km.
B) 4 km.
C) 2 km.
D) 12 km.
E) 36 km.

Question 25

The object left behind after the 1054 AD supernova explosion has been observed at the center of the Crab nebula. The object is a

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

Question 26

Unseen objects in our galaxy have been found by the bending effect they have on more distant stars' light passing near them. These small objects that don't emit light are calculated to have masses of about 10 × the mass of the Sun. Which is the best choice for these objects?

A) black hole
B) neutron star
C) white dwarf
D) main-sequence stars

Question 27

If the inner accretion disk around a black hole has a temperature of 10⁶ K, at what wavelength will it radiate the most energy? ( Hint : From Wien's law, λ T =3,000,000 where λ is in nm and T is in K.)

A) 10⁶ nm
B) 3 nm
C) 3 × 10⁶ nm
D) 1 nm
E) 3 × 10¹¹ nm

Question 28

The Schwarzschild radius of a 1- black hole is approximately

A) 3 km.
B) 1,500,000 km, the size of the Sun.
C) 150,000,000 km or 1 AU.
D) 3 × 10¹³ km or 1 pc.

Question 29

As material flows into a black hole as viewed from well outside the event horizon

A) the material will experience time dilation.
B) the material will become hotter.
C) the material will produce an absorption spectrum.
D) the material will appear to us to fall into the black hole very rapidly.
E) the material will experience time dilation and the material will become hotter.

Question 30

None of the pulsars emit pulses of visible light because

A) pulsars are too hot to emit visible light.
B) pulsars contain black holes that won't let visible light escape.
C) the gravitational field of a pulsar is so great that the visible light emitted is redshifted.
D) pulsars are too far away for the visible light to be bright enough to be detected at Earth.
E) A few pulsars do emit visible light pulses.

Question 31

The escape velocity at the event horizon around a black hole is

A) smaller than the speed of light.
B) equal to the speed of light.
C) much larger than the speed of light.
D) irrelevant since nothing (including light) can escape from a black hole.

Question 32

Fraud in science is rare because it is difficult to commit. Why is it difficult to commit fraud in science?

A) Science requires that experimental and theoretical findings be reproducible.
B) All scientists are bound by a code of ethics preventing them from publishing fraudulent work.
C) Scientific results are reviewed by other scientists before they are published.
D) Scientific journals only allow certain highly trusted individuals to publish their work.
E) Science requires that experimental and theoretical findings be reproducible and scientific results are reviewed by other scientists before they are published.

Question 33

The search for black holes involves searching for

A) single stars that emit large amounts of X-rays.
B) X-ray binaries where the compact companion has a mass in excess of 3 .
C) large spherical regions from which no light is detected.
D) pulsars with periods less than one millisecond.
E) pulsars that are orbited by planets.

Question 34

Millisecond pulsars that are very old are

A) believed to be the result of mass transfer from a companion that increased the spin of the pulsar.
B) all single objects.
C) not spinning as rapidly as they seem because they have four hot spots that produce the flashes.
D) X-ray binaries.
E) gamma-ray bursters.

Question 35

The singularity of a black hole

A) is found outside the event horizon.
B) is located within the event horizon.
C) can only be located if the black hole is in a binary system.
D) doesn't exist since all black holes have a finite size.

Question 36

At extremely high densities and temperatures, electrons can be forced to fuse with protons. This reaction produces

A) hydrogen.
B) helium and energy.
C) degenerate electrons.
D) neutrons and neutrinos.
E) large amounts of radio radiation.

Question 37

An isolated black hole in space would be difficult to detect because

A) there would be no light source nearby.
B) it would not be rotating rapidly.
C) it would be stationary.
D) very little matter would be falling into it.
E) there would be very few stars behind it whose light the black hole could block out.

Question 38

The escape velocity of an object depends on
I) the mass of that object.
II) the mass of the object trying to escape.
III) the distance from the center of the object and the escaping object.
IV) the speed of light.

A) I, II, III, & IV
B) I & II
C) I & III
D) I, II, & IV
E) I, III, & IV

Question 39

The material that accretes onto a neutron star or black hole is expected to emit X-rays because

A) the material will produce synchrotron radiation.
B) hydrogen nuclei begin to fuse and emit high-energy photons.
C) the material will become hot enough that it will radiate most strongly at X-ray wavelengths.
D) as the material slows down it converts thermal energy to gravitational potential energy.
E) None of the other choices are correct.

Question 40

A black hole can be thought of as

A) a very massive object of finite size.
B) a shell of material expanding from a white dwarf.
C) a massive body of infinitely small size.
D) a burnt out white dwarf.

Question 41

Complete the reaction: e + p → __ _____ ________; the reaction applies to ______ _____ _____.

A) n, white dwarfs
B) ν, neutron stars
C) n + ν , white dwarfs
D) n + ν , neutron stars

Question 42

Using the graph above of a pulsar in a binary orbit, what is the orbital period?

A) ˜6.75 hours
B) ˜5 hours
C) ˜12 hours
D) ˜3.5 hours

Question 43

The lighthouse in the above picture represents which model for which compact object?

A) lighthouse, neutron star
B) scientific, white dwarf
C) Earth-centered, neutron star
D) mathematical, Earth

Question 44

Gamma-ray bursts seem to be associated with violent events involving _______________.

A) planets
B) neutron stars
C) black holes
D) neutron stars or black holes

Question 45

The stability of a neutron star is expected only if a neutron star is a ____________.

A) solid
B) fluid
C) gas
D) All of the other choices are correct.

Question 46

What happens when a core's mass is less than 3 solar masses but greater than 1.44 solar masses?

A) Electron degeneracy pressure can no longer support the core and the electrons combine with the protons to generate neutrons and neutrinos, the neutrinos of which supply neutron degeneracy pressure to support the neutron star.
B) Electron degeneracy pressure can no longer support the core and the electrons combine with the protons to generate neutrons and neutrinos, the neutrons of which supply neutron degeneracy pressure to support the neutron star.
C) Electron degeneracy pressure supports the core of the white dwarf.
D) Electron degeneracy pressure can no longer support the core and the electrons combine with the protons to generate neutrons and neutrinos, the neutrinos of which supply neutron degeneracy pressure to support the black hole star.

Question 47

In the above graph of a pulsar in a binary, the motion of the pulsar from 2.75 hours to 3.5 hours is ___________________.

A) moving away from Earth
B) moving towards Earth
C) in motion perpendicular to the line-of-sight
D) in motion perpendicular to the line-of-sight followed by motion towards Earth

Question 48

What is the shape of the event horizon?

A) circle
B) line
C) sphere
D) square

Question 49

The figure shows an image of an isolated black hole. A black hole emits

A) light with wavelengths in the black color region.
B) no light from inside the event horizon.
C) light which is blueshifted to shorter wavelengths as it escapes.
D) light which is redshifted to shorter wavelengths as it escapes.

Question 50

Using the above graph of modulated light from a pulsar, how many planets can you determine to be in this system?

A) 0
B) 1
C) 2
D) 3

Question 51

Order the following from most to least dense:

A) black hole, neutron star, white dwarf
B) white dwarf, neutron star, black hole
C) black hole, white dwarf, neutron star
D) neutron star, white dwarf, black hole

Question 52

Which are compact objects?

A) black holes
B) neutron stars
C) white dwarfs
D) All of the other choices are correct.

Question 53

How fast does a pulsar initially spin?

A) 10 times per second
B) 1 time per second
C) 100 times per second
D) 1000 times per second

Question 54

Which object can be a pulsar?

A) white dwarf
B) neutron star
C) black hole
D) None of the other choices are correct.

Question 55

The white line is pointing to which object in the X-ray image above?

A) pulsar
B) neutron star
C) white dwarf
D) black hole

Question 56

What happens when a core's mass exceeds 3 solar masses and its density exceeds that which electron degeneracy pressure can support?

A) The core collapses into a black hole.
B) The core collapses into a neutron star.
C) The core collapses into a white dwarf.
D) The core collapses into a neutron star or a black hole.

Question 57

A star on the main sequence has 7 solar masses. The star will evolve into a _____ _______ and its core will be supported by ___ _____ ______.

A) white dwarf, electron degeneracy pressure
B) neutron star, neutron degeneracy pressure
C) black hole, no pressure (i.e., it will not be supported)
D) white dwarf, neutron star, or black hole; electron degeneracy, neutron degeneracy, and no pressure, respectively.

Question 58

What happens when a core's density exceeds that which electron degeneracy pressure can support?

A) The core collapses to a black hole.
B) The core collapses to a neutron star.
C) The core collapses to a white dwarf.
D) The core collapses to a neutron star or a black hole.

Question 59

The Crab pulsar emits light in which wavelength bands?

A) visual
B) gamma
C) X-ray
D) All of the other choices are correct.

Question 60

Rank the degenerate pressures from least supportive to most supportive:

A) electron, neutron, black hole
B) black hole, neutron, electron
C) neutron, electron
D) electron, neutron

Question 61

Neutron stars have densities roughly the same as that of the atomic nucleus.

Question 62

A(n) ____________________ periodically emits large amounts of X-ray radiation as material accretes around a neutron star or black hole.

Question 63

We expect neutron stars to spin rapidly because they conserve angular momentum.

Question 64

The ____________________ of a black hole is the radius from the black hole at which the escape velocity is equal to the speed of light.

Question 65

Neutron stars were first discovered in the 1930's.

Question 66

A(n) ____________________ is a rapidly spinning neutron star that accelerates charged particles near the poles of its magnetic field.

Question 67

Light that is shifted toward the color red due to the light passing very near a compact object is called ____________________.

Question 68

Pulsars could not be ordinary stars that are pulsating because the pulses are too short.

Question 69

LMC X-3 is a binary system that is believed to contain a black hole.

Question 70

To tell the difference between a neutron star and a black hole in an X-ray binary, we must find the temperature of the object.

Question 71

Energy lost by an isolated pulsar is carried away by a __ _____ ______.

Question 72

The event horizon marks the boundary within which the density is roughly the same as that of the atomic nucleus.

Question 73

The ____________________ of a black hole in a binary system can emit X-rays and allow us to detect the presence of the black hole.

Question 74

Many pulsars have periods that are gradually getting longer as the spinning neutron stars lose energy.

Question 75

Gamma-ray bursts lasting longer than two seconds appear to be related to ______________.

Question 76

An object of zero radius is known as a __________________.

Question 77

When a binary system loses orbital energy, it emits ___ _____ _______ radiation.

Question 78

Theory predicts that neutron stars may not exceed 3 solar masses.

Question 79

If the accretion disk around a black hole emits X-rays outside the event horizon, the X-rays can escape.

Question 80

The ____________________ theory describes pulsars as rotating neutron stars with strong magnetic fields that confine high-speed charged particles in two beams emanating from the magnetic poles of the neutron star.