Deck 22: Neutron Stars and Black Holes: Strange States of Matter

Question 1

Like most pulsars,the Crab Nebula neutron star is known only by its radio pulses.

Answer 1

False

Question 2

The escape speed for a black hole's event horizon is the speed of light.

Answer 2

True

Question 3

Newly formed neutron stars have weak magnetic fields which strengthen over time,due to the conservation of angular momentum.

Answer 3

False

Question 4

The density of a neutron star is comparable to the density of an atomic nucleus.

Question 5

All neutron stars must begin as millisecond pulsars just after their supernova creation.

Question 6

At the event horizon,time stops.

Question 7

Only neutrinos can go faster than the speed of light,as proved by Supernova 1987A.

Question 8

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

Question 9

Besides direct formation of a black hole in a hypernova,some think that mergers between neutron stars can create even longer-lived gamma ray bursts as well.

Question 10

Neutron stars seem to travel a good deal faster than most stars in orbit about the Galaxy.

Question 11

Astronomers believe that gamma-ray bursters emit radiation equally in all directions.

Question 12

A system of terrestrial-sized planets has been detected in orbit around a millisecond pulsar.

Question 13

All neutron stars are pulsars,but not all pulsars are neutron stars.

Question 14

Short duration gamma-ray bursts are explained as the merger of two neutron stars.

Question 15

Gamma-ray bursts seem to come primarily from neutron star binaries in the plane of our own Milky Way Galaxy.

Question 16

X-ray bursters are similar to novae,except the collapsed star is a neutron star,not a white dwarf.

Question 17

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

Question 18

If the rate at which a pulsar is slowing down is found,this helps us find the time at which it was produced by the supernova.

Question 19

The Schwarzschild radius of a black hole is about 3 km per solar mass; it is amazingly linear over a wide range of masses.

Question 20

X-ray bursts and gamma ray bursts have the same distribution pattern in the sky.

Question 21

In the Lighthouse Model,

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

Question 22

The vast majority of pulsars are known only from their pulses in:

A) X-rays.
B) gamma-rays.
C) visible light.
D) microwaves.
E) radio waves.

Question 23

Two important properties of young neutron stars are:

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

Question 24

Which of these does NOT exist?

A) a million solar mass black hole
B) a 6 solar mass black hole
C) a 6.8 solar mass neutron star
D) a 1.0 solar mass white dwarf
E) a 0.06 solar mass brown dwarf

Question 25

Neutron stars have:

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

Question 26

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

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

Question 27

Very rapid time variations help establish the tiny size of many X-ray sources,showing they must be collapsed objects of some kind.

Question 28

Pulsars:

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

Question 29

The energy from the accretion disk around a black hole would show gravitational redshift due to its immense gravity and tidal distortion of space there.

Question 30

What would happen if mass is added to a 1.4 solar mass white dwarf?

A) The star would explode as a nova.
B) The star's radius would increase.
C) The star would immediately collapse into a black hole.
D) The star would erupt as a carbon detonation (type I) supernova.
E) The core would collapse as a type II supernova.

Question 31

What compelling evidence links pulsars to neutron stars?

A) Both pulsars and neutron stars can be found in globular star clusters.
B) Pulsars are known to evolve into neutron stars.
C) Only a small, very dense source could rotate that rapidly without flying apart.
D) Pulsars are always found in binary systems with neutron stars.
E) Both pulsars and neutron stars have been discovered near the Sun.

Question 32

Special relativity predicts that light bends near dense objects.

Question 33

Neutron stars and black holes are formed by:

A) the star formation process.
B) mass transfer in binary star systems.
C) novae.
D) type I supernovae.
E) type II supernovae.

Question 34

Neutron stars do NOT have:

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

Question 35

The average density of neutron stars approaches:

A) a million times that of normal matter.
B) a million times that of even a white dwarf.
C) about 10¹⁷ kg/m³, similar to the density of atomic nuclei.
D) about 10¹⁸ times that of water.
E) infinity.

Question 36

What makes the Crab Nebula supernova remnant unusual as a supernova remnant?

A) It is the biggest supernova remnant visible.
B) It is the remnant of a supernova that was observed in the 20th century.
C) It is the nearest supernova remnant.
D) It is the oldest supernova remnant known.
E) It is the remnant of a supernova observed by humans.

Question 37

In a neutron star,the core is:

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

Question 38

What makes the Crab pulsar somewhat unusual among pulsars in general?

A) It is the most intense source of X-rays in the sky.
B) It is the fastest pulsar known.
C) It is the oldest pulsar observed.
D) Its period is not regular like other pulsars.
E) It is rather bright at visible wavelengths.

Question 39

Mercury's orbital precession is adequately explained by Newton's Law of Gravity.

Question 40

In the Lighthouse model:

A) pulsars are observable only if they lie in the galactic plane.
B) pulsars are navigational devices created by interstellar navigators as discovered by Jocelyn Bell in 1967.
C) all pulsars have their poles pointed directly at us or they would be not observable.
D) if the beams sweeps across us, we can observe the pulse.
E) the period of pulsation must speed up as the neutron star continues contracting.

Question 41

Redshift measurements of the visible afterglow of a gamma-ray burst show that these objects are:

A) in the solar neighborhood.
B) in the Milky Way Galaxy.
C) in the Local Group.
D) billions of light-years away.
E) at the most extreme observable distances.

Question 42

In contrasting the distribution of the X-ray and gamma-ray bursts,we find:

A) gamma ray bursts are far closer to us, so they appear more luminous.
B) gamma ray bursts are far beyond our Galaxy, at cosmological distances, and spread all over the sky, not in the plane of our Galaxy.
C) gamma ray bursts are more closely associated with open than globular clusters.
D) gamma ray bursts can repeat, while the X-ray bursts do not.
E) gamma ray bursts can be observed from the ground, but X-rays are blocked by the ionosphere for ground based observers.

Question 43

The supernova of 1054 AD produced:

A) a remnant still visible to the naked eye, the Crab Nebula, M-1.
B) a pulsar with a period of 33 milliseconds, visible optically.
C) the closest known neutron star to our Sun.
D) the most famous black hole.
E) no remaining visible trace, as it was a type I supernova.

Question 44

The mass range for neutron stars is:

A) 0.08 to .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 45

Which of the following can actually escape from inside a black hole's event horizon?

A) neutrinos
B) electrons
C) very high energy gamma-rays
D) gravitons
E) None of the above

Question 46

You would expect millisecond pulsars to be:

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

Question 47

Relatively long duration gamma-ray bursts are produced by:

A) novae.
B) supernovae.
C) hypernovae.
D) neutron star mergers.
E) black hole mergers.

Question 48

Most pulsars have a measured mass of:

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

Question 49

Whose work with SETI led to the discovery of pulsars in 1967?

A) Jocelyn Bell
B) Sir Bernard Lovell
C) Anthony Hewish
D) Martin Schwarzschild
E) Stephen Hawking

Question 50

A critical difference between millisecond and normal pulsars is that:

A) the millisecond ones are not associated with the galaxy, but scattered everywhere.
B) the millisecond ones are speeding up, but normal pulsars slow down over time.
C) the millisecond ones must eventually collapse into black holes.
D) the millisecond ones all have planets, while normal ones do not.
E) millisecond ones are only found in globular clusters, while normal ones are not.

Question 51

Almost half of all known millisecond pulsars are found in what type of object?

A) giant molecular clouds
B) open clusters
C) globular clusters
D) emission nebulae
E) supernova remnants

Question 52

To which of these phenomena are X-ray busters most similar?

A) novae
B) planetary nebulae
C) type I supernovae
D) type II supernovae
E) hypernovae

Question 53

What are X-ray bursters?

A) They are the central sources of energy for planetary nebulae.
B) They are very massive stars that explode as supernovae, emitting bursts of X- rays and gamma-rays in the process.
C) They are rapidly rotating black holes whose precession points their poles toward us on occasion.
D) They are violent energy sources known to lie at the heart of the Milky Way and similar massive galaxies.
E) They are neutron stars on which accreted matter builds up, then explodes in a violent nuclear explosion.

Question 54

Which of the following is NOT a property of a pulsar?

A) period of 1.34 seconds
B) over time, the period is gradually increasing
C) emissions only in the visible part of the spectrum
D) each pulse consisting of a 0.01 second burst of radiation
E) time interval between pulses is very uniform

Question 55

While most neutron stars are also pulsars,an older "bare" neutron star was captured in rapid motion only 200 lightly years distant by:

A) Arecibo Radio Observatory.
B) the Keck Telescopes used as an interferometer.
C) the Chandra X-ray observatory.
D) the Hubble Space Telescope.
E) the Spitzer Infrared Space Telescope.

Question 56

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

Question 57

A proposed explanation for gamma-ray bursters is:

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

Question 58

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

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

Question 59

The Swift satellite observes what portion of the electromagnetic spectrum?

A) gamma-ray
B) X-ray
C) ultraviolet
D) optical
E) All of the above

Question 60

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

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

Question 61

Why do scientists describe the theory of gravity as "incomplete"?

A) It does not incorporate a description of matter on a very small scale.
B) It does not explain why light bends near a dense object.
C) It does not agree with the expansion of the universe.
D) The gravity waves it predicts have not been observed.
E) It does not explain the effects on time from a massive object.

Question 62

A hypernova creates:

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

Question 63

When observing an object,such as a space ship that is moving very quickly relative to you,the length of objects on that object will appear to be:

A) longer than when they are at rest.
B) the same length as when they are at rest.
C) shorter than when they are at rest.
D) narrower than when they are at rest.
E) wider than when they are at rest.

Question 64

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 inversely proportion to the radius of the body.
D) Gravity is the opposite of the electromagnetic force.
E) Gravity can affect only massive particles, not massless photons.

Question 65

The largest known black holes:

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

Question 66

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

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

Question 67

The key to identifying a black hole candidate in a binary system is that:

A) one of the two stars cannot be seen.
B) the unseen companion in the system must have a sufficiently high mass.
C) the unseen star is a contact binary.
D) the system must be a very strong source of radio emissions.
E) the visible companion must be an evolving main sequence or giant star.

Question 68

The equivalence principle says that a person in an elevator that is in free fall feels the same acceleration as:

A) a person in an elevator going up with an acceleration of g.
B) a person in space, far from any gravitational source accelerating at g.
C) a person in an elevator going down with an acceleration of g.
D) a person in space, far away from any gravitational source with no acceleration.
E) a person in orbit of Earth accelerating at g upward.

Question 69

The observed slowing of a clock in the vicinity of a black hole is a prediction of:

A) the Roche Limit.
B) Special relativity.
C) General relativity.
D) Stellar nucleosynthesis.
E) the Cosmological Principle.

Question 70

As a spaceship's velocity gets closer to the speed of light:

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

Question 71

What is Cygnus X-1?

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

Question 72

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 73

Which of the following is NOT an argument for Cygnus X-1's being a true black hole?

A) Spectroscopic data suggests hot gas is flowing from the companion B star onto Cygnus X-1.
B) The mass of the visible B star is even greater than Cygnus X-1, at around 25 solar masses.
C) Cygnus X-1's mass is estimated to be about 10 solar masses.
D) X-rays from Cygnus X-1 vary on time scales as short as a millisecond.
E) X-ray observations around the object support a temperature of several million K.

Question 74

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 75

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

A) Gamma-ray bursts
B) Radio waves if the matter was traveling fast enough
C) Visible light
D) X-rays if the matter was dense
E) Nothing

Question 76

A method for identifying a black hole is to:

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

Question 77

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

A) less than 1.0 solar masses.
B) greater than Schwartzschild's limit of 3 solar masses.
C) Chandrasekhar's limit of 1.4 solar masses.
D) between 1.4 and 2.0 solar masses.
E) greater than 25 solar masses.

Question 78

Which of the following are attracted by gravity?

A) antimatter
B) any object with mass
C) electromagnetic radiation
D) neutrinos
E) All of the above

Question 79

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

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

Question 80

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

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