Deck 14: Neutron Stars and Black Holes: Strange States of Matter

Question 1

The "pulse" from a pulsar is due to the rapidly expanding and contracting outer shell of the star.

Answer 1

False

Question 2

Pulsars are created in a Type I supernova.

Answer 2

False

Question 3

Gamma- ray bursters are all found to be within our galaxy.

Answer 3

False

Question 4

No planets have ever been found around any pulsars.

Question 5

A hypernova is a gamma- ray burster that forms a black hole as well.

Question 6

Most pulsars are known only as radio sources, but a few of the younger ones, like the Crab and Vela, also give off visible and even X- ray energy.

Question 7

Planets similar to our Jovians have been found orbiting pulsars.

Question 8

An X- ray burster is similar to a nova.

Question 9

The pulses from a pulsar are most likely coming from localized areas near the magnetic poles.

Question 10

While most pulsars slow down over time, millisecond pulsars spin faster due to mass transfer from a close companion.

Question 11

All neutron stars seen from Earth are pulsars.

Question 12

Gamma- ray bursters seem scattered randomly over the entire sky.

Question 13

In a neutron star, the electrons in the core are all in contact with each other.

Question 14

Stars of less than 8 solar masses will not go supernova.

Question 15

Neutron stars are 100,000 times denser than white dwarfs.

Question 16

Millisecond pulsars are never members of close binary systems.

Question 17

Planet- sized bodies have been detected around pulsars.

Question 18

Newly- formed neutron stars start with weak magnetic fields, but they strengthen over time into pulsars.

Question 19

In a neutron star, the protons and electrons are fused together, leaving only neutrons.

Question 20

A neutron star is what can remain after a Type II supernova explosion has destroyed the rest of the star.

Question 21

An object more massive than the Sun, but roughly the size of a city, is a

A) red dwarf.
B) neutron star.
C) white dwarf.
D) black dwarf.
E) brown dwarf.

Question 22

No optical traces have been found of the gamma- ray bursters.

Question 23

No communication is possible across an event horizon.

Question 24

Some gamma- ray bursters may be due to the merger of a neutron star and a black hole.

Question 25

Only high- energy gamma rays can escape the event horizon of a black hole.

Question 26

Because of their immense size, black holes moving through space consume huge quantities of interstellar matter along their paths.

Question 27

Einstein's prediction of the curvature of space was confirmed by the 1919 total solar eclipse.

Question 28

In a neutron star, the core is

A) no longer rotating.
B) primarily iron and silicon.
C) made of compressed neutrons in contact with each other.
D) electrons and protons packed so tightly they are in contact.
E) constantly expanding and contracting.

Question 29

Two important properties of young neutron stars are

A) extremely slow rotation and a strong magnetic field.
B) extremely rapid rotation and a strong magnetic field.
C) extremely rapid rotation and a weak magnetic field.
D) no rotation and a weak magnetic field.
E) no rotation and no magnetic field.

Question 30

Both space and time are warped near the strong gravitational fields of neutron stars and black holes.

Question 31

Any main- sequence star over 25 solar masses will probably retain enough matter in its core after its supernova to make a black hole.

Question 32

All gamma- ray bursters have the same fundamental driving mechanism, although we don't yet know whether it is a hypernova or a merger of two neutrons stars.

Question 33

Even if a probe were in a stable orbit near a black hole, we would still observe its signals redshifted by the gravitational field of the black hole.

Question 34

The closer the observer comes to the event horizon, the slower his watch will appear to run to a distant observer.

Question 35

The escape speed at the event horizon of a black hole is c, 300,000 km/sec.

Question 36

All the gamma- ray bursters measured to date have distances of millions or even billions of light-years.

Question 37

All Type II supernovae produce neutron stars when they collapse.

Question 38

Special relativity says that c, the speed of light, is the maximum velocity for both matter and energy in our universe.

Question 39

The Schwarzschild radius of a black hole is about 3 km per solar mass.

Question 40

The presently known laws of physics clearly describe the conditions inside a black hole's event horizon.

Question 41

Most pulsars have a measured mass of

A) between 2 and 4 solar masses.
B) greater than 10 solar masses.
C) about 1.4 solar masses.
D) less than 1.0 solar masses.
E) 5.2 solar masses.

Question 42

The mass range for neutron stars is

A) 0.08 to 0.4 solar masses.
B) 0.4 to 3 solar masses.
C) 1.4 to 3 solar masses.
D) 3 to 8 solar masses.
E) 6 to 11 solar masses.

Question 43

Three terrestrial- sized planets in orbits of a fraction of an AU have been found near

A) a magnetar.
B) a white dwarf.
C) Supernova 1987A.
D) Cygnus X- 1.
E) a millisecond pulsar.

Question 44

Who discovered the first four pulsars?

A) Carl Sagan
B) Jocelyn Bell
C) Anthony Hewish
D) Stephen Hawking
E) Martin Schwartzschild

Question 45

A proposed explanation for gamma- ray bursters is

A) coalescence of a neutron star binary.
B) hypernova- making black holes and bipolar jets.
C) collisions between two white dwarfs.
D) Both A and B are possible.
E) All three are possible.

Question 46

Which statement about gamma ray bursters is NOT correct?

A) In seconds, they radiate enormous amounts of energy.
B) They seem to be coming from far beyond our own Milky Way.
C) The beams may be bipolar ejections from the hypernova formation of black holes.
D) Millisecond flickering implies they are tiny in size.
E) They are scaled up X- ray bursters, with more massive objects involved.

Question 47

In the Lighthouse Model,

A) the period of pulsation must speed up as the neutron star continues collapsing.
B) the star literally turns on and off like a lighthouse beacon.
C) the period of pulsation slows down due to the drag of the remnant on its field.
D) all pulsars must have their poles pointed directly toward us.
E) if the beam sweeps across us, we will detect a pulse of radiation.

Question 48

Most pulsars are observed only as sources.

A) X- ray
B) visible lighthouse
C) gamma- ray burster
D) ultraviolet repeating
E) radio

Question 49

X- ray bursters occur in binary star systems. The two types of stars that must be present to make up such an object are

A) a white dwarf and a main- sequence star.
B) a white dwarf and a neutron star.
C) a contact binary system of two red giants.
D) two neutron stars in a mass transfer binary.
E) a main- sequence or giant star and a neutron star in a mass transfer binary.

Question 50

Which of these does NOT exist?

A) a 6 solar mass black hole
B) a 1.8 solar mass neutron star
C) a 0.06 solar mass brown dwarf
D) a 1.5 solar mass white dwarf
E) a million solar mass black hole

Question 51

Neutron stars have

A) periods of days or weeks.
B) weak or non- existent magnetic fields.
C) monopolar fields that switch polarity every rotation.
D) very strong bipolar magnetic fields.
E) no relation to pulsars.

Question 52

A hypernova creates

A) millisecond- duration gamma- ray bursts.
B) a pulsar.
C) a neutron star.
D) a black hole.
E) Both B and C are correct.

Question 53

What makes the Crab Nebula pulsar unusual among other pulsars?

A) It is a magnetar, with far more intense magnetic fields than any other.
B) Its period is much less regular than other pulsars.
C) It is the fastest spinning known pulsar.
D) It is relatively bright in shorter wavelengths, like visible and X- rays.
E) It is the oldest known pulsar.

Question 54

You would expect millisecond pulsars to be

A) rotating slowly.
B) most common in open clusters.
C) part of a binary system.
D) isolated in space.
E) collapsing rapidly.

Question 55

Pulsars

A) generally form from 25- solar- mass stars.
B) spin very rapidly when they're young.
C) emit radio in all directions.
D) are the cause of gamma- ray bursts.
E) spin very slowly when they're young, and gradually spin faster as they age.

Question 56

In a hypernova, a very energetic supernova creates a

A) set of planets to orbit their neutron star host.
B) millisecond pulsar.
C) very visible supernova remnant.
D) black hole.
E) white dwarf and its planetary nebula.

Question 57

What would happen if more mass was added to a 1.4- solar- mass neutron star?

A) It could eventually become a black hole, via a hypernova explosion.
B) It would blow off mass as an X- ray burster.
C) It would erupt as a Type I supernova.
D) It would grow larger, temporarily becoming a red giant again.
E) All of its protons and electrons would turn into quarks.

Question 58

The supernova of 1054 AD produced

A) a remnant still visible to the naked eye.
B) a pulsar with a period of 33 milliseconds, visible optically.
C) the most famous black hole.
D) the closest known neutron star to our Sun.
E) no remaining visible trace, as it was a Type I supernova.

Question 59

Neutron stars do NOT have

A) masses greater than 1.4 solar masses.
B) strong magnetic fields.
C) rotation periods comparable to the Sun's.
D) sizes comparable to large cities.
E) large surface gravities, compared to the Sun.

Question 60

Two- thirds of all known millisecond pulsars are found in what type of object?

A) open clusters
B) globular clusters
C) extremely distant galaxies
D) emission nebulae
E) giant molecular clouds

Question 61

The densely packed neutrons of a neutron star cannot balance the inward pull of gravity if the total mass is

A) not at least 25 solar masses.
B) between 1.4 and 2.0 solar masses.
C) Chandrasekhar's limit of 1.4 solar masses.
D) greater than Schwartzschild's limit of 3 solar masses.
E) less than 1.0 solar masses.

Question 62

The model for pulsars explains why there are a lot more neutron stars than pulsars, since most are not at the correct angle for us to observe their pulses.

A) lighthouse
B) Bell
C) Einstein
D) Hawking
E) relativistic

Question 63

Which statement about black holes is true?

A) They form from 1.4 solar mass stars.
B) They form an event horizon at twice the Schwartzschild radius.
C) Their escape velocity is greater than the speed of light.
D) Their event horizon is a physical surface boundary.
E) Their main- sequence mass was 5- 10 solar masses.

Question 64

Which are the two most popular candidates for gamma- ray bursters?

A) mergers of two black holes, and merger of a neutron star and a white dwarf
B) collisions between a white dwarf and a giant, and merger of two neutron stars
C) formation of uranium in the core of a supergiant, and collisions of white dwarfs
D) hypernova making pulsars, and mergers of two white dwarfs
E) hypernova making a black hole, and merger of two neutron stars

Question 65

The Schwartzschild radius for a 12 solar mass star is

A) 4 km.
B) 15 km.
C) 36 km.
D) 100 km.
E) 3000 km.

Question 66

stars are solid, extremely dense objects.

A) Neutron
B) Proton
C) X- ray
D) Electron
E) Wolf- Rayet

Question 67

A method for identifying a black hole is to

A) look for its effects on a nearby companion.
B) search for their pulsar signal.
C) search for radio waves from the accretion disk.
D) look for voids in the star fields.
E) locate a visible star that disappears when the black hole passes in front of it.

Question 68

If the Sun were replaced by a one- solar- mass black hole,

A) we would immediately escape into deep space, driven out by its radiation.
B) our clocks would all stop.
C) all terrestrial planets would fall in immediately.
D) we would still orbit it in a period of one year.
E) life here would be unchanged.

Question 69

Extra mass dumped on a white dwarf creates a nova, but if dumped on a neutron star, it creates

A) an X- rays burster.
B) a millisencond pulsar.
C) a black hole.
D) a pulsar.
E) a gamma- ray burster.

Question 70

Most pulsars emit

A) visible light.
B) radio waves.
C) X- rays.
D) gamma rays.
E) nothing.

Question 71

The largest known black holes

A) can be no bigger than the Earth, like white dwarfs.
B) can be no more than 1.4 solar masses, according to Chandrasekhar.
C) create the dark nebulae in the plane of the Milky Way.
D) lie in the cores of the most massive galaxies.
E) can be no bigger than a small city, just like neutron stars.

Question 72

If light from a distant star passes close to a massive body, the light beam will

A) change color to a shorter wavelength.
B) slow down.
C) continue moving in a straight line.
D) bend towards the star due to gravity.
E) accelerate due to gravity.

Question 73

The supernova that created the Crab nebula and its pulsar was seen on Earth in the year

A) 1604 BC.
B) 1054 BC.
C) 1054 AD.
D) 1592 AD.
E) 1604 AD.

Question 74

What can we detect from matter that has crossed an event horizon?

A) X- rays if the matter was dense
B) visible light
C) gamma- ray bursts
D) radio waves if the matter was traveling fast enough
E) nothing

Question 75

An observer on a planet sees a spaceship approaching at 0.5c. A beam of light projected by the ship would be measured by this observer to travel at

A) 0.25c.
B) 0.5c.
C) c.
D) 1.5c.
E) 2.5c.

Question 76

What is Cygnus X- 1?

A) the first gamma- ray burster to be spotted in other wavelengths as well
B) the strongest X- ray eclipsing binary system in the sky
C) a millisecond pulsar with three Earth- like planets around it
D) the brightest star in the constellation Cygnus
E) the leading candidate for an observable black hole binary system

Question 77

What explanation does general relativity provide for gravity?

A) Gravity is the result of curved spacetime.
B) Gravity is directly proportional to the mass of the attracting body.
C) Gravity is the opposite of the electromagnetic force.
D) Gravity can affect only massive particles, not massless photons.
E) Gravity is inversely proportional to the radius of the body.

Question 78

As a spaceship nears an event horizon, a clock on the spaceship will be observed

A) to run backwards.
B) to run slowly.
C) to run faster.
D) to run the same as one on Earth.
E) to stop.

Question 79

As a spaceship's velocity gets closer to the speed of light with respect to an external observer, that observer will report that

A) its length will decrease and its clock will run more slowly.
B) its length will decrease and its clock will run faster.
C) its length will increase and its clock will run more slowly.
D) its length will increase and its clock will run faster.
E) None of these will happen.

Question 80

Which of these is NOT an argument for Cygnus X- 1 being a black hole?

A) It is the third strongest source of X- rays in the sky.
B) The X- rays from the compact source vary in as little as a millisecond.
C) Spectroscopic data suggests hot gas is flowing toward the X- ray source.
D) The mass of the visible star is greater than that of the X- ray source.
E) The mass of the X- ray source is about 10 solar masses.