Deck 14: Neutron Stars and Black Holes

Question 1

All supernova remnants contain pulsars.

Answer 1

False

Question 2

A neutron star must have a mass greater than 2.4 solar masses.

Answer 2

False

Question 3

A compact object with a mass of 4 solar masses must be a black hole.

Answer 3

True

Question 4

The first detection of gravitational waves, by the Laser Interferometer Gravitational Wave Observatory, was announced in 2016.

Question 5

Neutron stars are supported by _____.

A) neutron gas pressure
B) hydrogen gas pressure
C) electron degeneracy pressure
D) neutron degeneracy pressure
E) hydrogen degeneracy pressure

Question 6

Pulsars can be created by neutron stars or black holes.

Question 7

The oldest pulsars are billions of years old.

Question 8

A compact object with a mass of 1.1 solar masses could ____.

A) be a neutron star or a black hole
B) be a neutron star, but not a black hole
C) be a black hole, but not a neutron star
D) not be a black hole or neutron star
E) not be a black hole or neutron star

Question 9

A hypernova is one of several types of events that create a gamma ray burst.

Question 10

The event horizon is located at the Schwarzschild radius.

Question 11

Jets are composed of matter and antimatter produced in the poles of a compact object.

Question 12

Gamma ray bursts never last longer than a minute.

Question 13

A pulsar emits bursts of radio photons.

Question 14

Most neutron stars are the remnants of _____ explosions.

A) type II supernovae
B) type Ia supernovae
C) type Ib supernovae
D) novae
E) planetary nebulae

Question 15

The laws of physics demand that a neutron star has a maximum mass of ____ solar mass(es).

A) 1
B) 1.4
C) 3
D) 8
E) 20

Question 16

Which statement best describes a neutron star's formation as a supernova explodes and the core begins to collapse inward?

A) neutrinos and antineutrinos combine into neutrons
B) electrons and protons combine into neutrons and neutrinos
C) electrons and protons combine into neutrons and neutrinos
D) electrons and positrons combine into neutrons and neutrinos
E) protons and antiprotons combine into neutrons and neutrinos

Question 17

X-ray bursters are caused by black holes.

Question 18

Pulsars were the first evidence of extraterrestrial life.

Question 19

Many pulsars are not associated with supernova remnants.

Question 20

A neutron star is created when a(n) ___.

A) collapsing stellar core exceeds the Schwarzschild limit
B) stellar core ignites iron fusion
C) collapsing stellar core exceeds the Chandrasekhar limit
D) stellar core exceeds the Roche limit
E) collapsing stellar core exceeds the Hawking limit

Question 21

An X-ray burster occurs in a pulsar when ____.

A) accreted helium suddenly fuses in a nova-like explosion
B) the Chandrasekhar limit is exceeded and the object collapses
C) carbon deflagration destroys the object
D) it merges with a binary companion
E) hydrogen fusion ignites in an accretion disk around it

Question 22

Most of the energy emitted by a pulsar _____.

A) is carried away as a 'pulsar wind' of high-speed atomic particles
B) produces strong gravitational waves that radiate for several light years
C) ionizes the supernova remnant around the pulsar
D) is in the form of neutrinos
E) is carried away by the high-energy beam emerging from the poles of the pulsar

Question 23

Astronauts approaching a black hole would observe that _____.

A) time appears to slows down for them
B) time appears to speed up for external observers
C) they become squashed flat-their heads and feet are pushed together by gravitational tides
D) they become stretched thin-their heads and feet are pulled apart by gravitational tides
E) nothing appears to change

Question 24

The highest luminosity burst of radiation observed from a pulsar is the result of _____.

A) the pulsation of a neutron star's surface
B) a "hot spot" that rotates around the equator of a pulsar
C) a spinning beam of radiation emerging from the pulsar's poles
D) the rotation of an accretion disk transferring matter to the pulsar's surface
E) the revolution of a binary companion that eclipses the pulsar, then reveals it

Question 25

If the Sun was replaced by a black hole of equal mass, Earth would _____.

A) fall into the black hole on a virtually straight path
B) spiral in to the black hole over several months
C) spiral in to the black hole over the course of several decades
D) continue in its normal orbit
E) spiral away from the black hole, pushed by gravitational waves

Question 26

When viewed from nearby, a black hole in empty space _____.

A) has a funnel shape, extending to the event horizon
B) glows in X-rays and gamma-rays from superheated surface
C) is invisible
D) would look like a dark sphere the size of Earth
E) emits blackbody radiation only

Question 27

Pulsars were discovered because they _____.

A) provide the energy to ionize supernova remnants
B) radiate gravitational waves
C) absorb matter from a binary companion through an accretion disk
D) emit short, regular bursts of radiation
E) undergo nova eruptions on a regular period of a few years

Question 28

A stellar core with a mass greater than 3 solar masses will collapse until it reaches _____.

A) the radius of Earth
B) the radius of Mt. Everest
C) the radius of a grain of sand.
D) the radius of a helium atom
E) a radius of zero

Question 29

Gas falling into a black hole:

A) is heated to millions of degrees through the loss of gravitational energy
B) is cooled to near absolute zero through the loss of gravitational energy
C) releases energy, all of which is absorbed by the black hole
D) never reaches the black hole due to the effect of time dilation
E) orbits the black hole but cannot cross the event horizon

Question 30

An astronomer examining a compact object could conclude that it was a black hole if it _____.

A) emits regular pulses of radiation
B) has a defined event horizon that emits X-rays
C) has an accretion disk
D) has a mass greater than 1.4 solar masses
E) has a mass greater than 3 solar masses

Question 31

Most pulsars _____.

A) speed up their rotation as they age
B) become more luminous as they age
C) emit lower energy radiation as they age
D) emit higher energy radiation as they age
E) slow down their rotation as they age

Question 32

In a binary system containing two neutron stars, the objects will ____.

A) radiate orbital energy away as gravitational radiation and move farther apart
B) radiate orbital energy away as gravitational radiation and move closer together
C) exchange mass until their orbital periods become equal
D) exchange mass until they are in synchronous rotation
E) exchange angular momentum, lengthening the period of the pulsar

Question 33

Pulsar planets are _____.

A) huge gas planets that could be classified as brown dwarfs
B) asteroids captured from interstellar space
C) observed, but not fully understood
D) predicted, but have not been observed
E) Earth-like, and may harbor life

Question 34

The event horizon of a black hole is the point where _____.

A) the mass of the black hole is concentrated in a singularity
B) the accretion disk around the black hole contacts its surface
C) the escape velocity equals the speed of light
D) tidal forces ionize infalling gas
E) an infalling particle reaches equilibrium with radiation pressure

Question 35

Supernova remnants _____.

A) always contain pulsars, because pulsars supply the ionizing radiation
B) often last longer than a pulsar does, so the central pulsar may no longer be visible
C) rarely contain pulsars, because pulsar radiation disrupts the remnant
D) may not contain a pulsar, if the supernova explosion kicked the pulsar away at high speed
E) never contain pulsars

Question 36

Millisecond pulsars _____.

A) are created in supernova explosions of the most massive stars
B) result from the collision of two neutron stars
C) represent the youngest pulsars detected
D) result from long-term mass transfer from a companion star
E) are a theoretical prediction that has not been observed

Question 37

The first confirmed black hole, Cygnus X-1, was regarded as proof that black holes exist because it

A) is a compact object in a binary system
B) emits X-rays from a hot accretion disk
C) is accreting matter from a main-sequence companion
D) has a period of 5.6 days
E) has a mass of ten solar masses

Question 38

A black hole is _____.

A) an object so dense that light cannot escape its surface
B) a neutron star that has exceeded the Chandrasekhar limit
C) a theoretical model that has never been observed
D) an observed object that is not well understood
E) the result of a neutron star merger

Question 39

Neutron stars radiate most of their energy in the ____ wavelength band(s).

A) radio and infrared
B) radio and X-ray
C) visible
D) visible and gamma-ray
E) X-ray and gamma-ray

Question 40

Neutron stars must ____.

A) rotate very rapidly
B) be very luminous
C) have weak magnetic fields
D) have a mass greater than three solar masses
E) have about the same surface temperature as the star that created them

Question 41

Matter falling onto a compact object, such as a neutron star or black hole, forms a(n):

A) accretion disk
B) binary star
C) gamma-ray burst
D) pulsar
E) magnetar

Question 44

The jets emitted by compact objects are made of _____.

A) X-rays
B) atomic nuclei
C) neutrons
D) neutrinos
E) positrons

Question 45

A compact object emitting very regularly spaced bursts of radio energy is known as a(n) _______________.

Question 46

What is the approximate density of a neutron star?

A) 10² g/cm³
B) 10 ⁵  g/cm ³
C) 10 ¹⁵  g/cm ³
D) 10^{2 5}  g/cm ³
E) 10 ⁵⁰  g/cm ³

Question 47

What are the physical properties neutron stars, and how does theory predict these properties?

Question 48

The orbits of binary pulsars will get smaller because of _______________ radiation.

Question 49

Jets from compact objects are explained by the effect of _____.

A) magnetic fields
B) gravitational waves
C) angular momentum
D) mass transfer
E) pulsar winds

Question 50

Gamma ray bursts _____.

A) last minutes to hours
B) are detected primarily in the disk of the galaxy
C) occur without warning
D) are not associated with any observable event
E) are detected only a few times per year

Question 51

A hypernova is a violent event caused by _____.

A) the merger of two neutron stars
B) the collapse of a rapidly rotating massive star
C) the fusion of a layer of degenerate helium deposited on the surface of a neutron star
D) carbon deflagration in a neutron star
E) the crossing of jets from two compact objects

Question 52

Gamma ray bursts are ____.

A) too weak to affect life on Earth
B) an important influence on mutation and evolution
C) the cause of the spectacular auroras at high latitudes
D) triggers for solar flares and coronal mass ejections
E) capable of causing mass extinction events

Question 53

A star with a mass of 10 to 20 solar masses will produce a(n) _______________ remnant after a supernova explosion.

Question 54

Astronomers detect _______________ of ionized gas moving perpendicular to the plane of many accretion disks.

Question 55

Gamma ray bursts were first recorded while trying to detect _____.

A) solar flares
B) the Aurora Borealis
C) nuclear reactor accidents
D) nuclear tests
E) particle accelerator leakage

Question 56

The _______________ model explains pulsars using beams of radiation that sweep around the sky.

Question 57

A magnetar is a type of ____.

A) hypernova
B) neutron star
C) black hole
D) jet
E) X-ray burster

Question 58

What evidence did astronomers use to prove jets travel in opposite directions?

A) spectral lines from fast-moving red- and blue-shifted ionized gas
B) gamma ray emission spectra
C) magnetic tubes in accretion disks
D) mass transfer from a binary star to a compact companion
E) pulsar rotation periods

Question 59

A pulsar wind is composed of high-speed __________.

A) charged particles
B) photons
C) gamma rays
D) helium atoms
E) hydrogen atoms

Question 60

As light travels out of a gravitational field, it loses energy, and its wavelength grows longer. This is known as the _____________.

Question 61

Why are black holes called "black"?

Question 62

Any compact object with a mass greater than _______________ solar masses must form a black hole.

Question 63

The mass of a black hole concentrated in an infinitesimally small volume with zero radius, is known as a(n) _______________.

Question 64

What prediction does general relativity make for pulsars in a binary system?

Question 65

Extremely old pulsars that have experienced large amounts of mass transfer may become _______________ pulsars.

Question 66

Schwarzschild showed how the _______________ of the event horizon depends only on the mass of the black hole.

Question 67

Why do some supernovae form neutron star remnants instead of white dwarfs?

Question 68

A supermassive, rapidly rotating star may generate a gamma-ray burst in a(n) _______________ eruption.

Question 69

A neutron star, which generates gamma-ray bursts due to "starquakes" on its surface, is called a(n) _______________.

Question 70

Explain the "Lighthouse Model" of pulsars.

Question 71

What observational properties of pulsars allowed astronomers to discover them as a new type of object?

Question 72

Imagine an astronaut falling into a black hole. Describe the effects that the astronaut would experience firsthand, and the changes that an external observer would see.

Question 73

Why are millisecond pulsars often found in binary systems with small red- or brown-dwarf companions?

Question 74

What observational evidence proved that gamma ray bursts do not come from objects in our galaxy?

Question 75

What is a "hypernova," and how do they produce observable gamma ray bursts?