Astronomy Chapter 22 Neutron Stars and Black Holes

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

False

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

False

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

False

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. True False

False

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

False

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

False

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

False

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

False

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

False

Special relativity predicts that light bends near dense objects. True False

False

There is no difference in the light curve for a hypernova and the light curve for a supernova II; the two events are distinguished from other properties. True False

False

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

False

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

True

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

True

At the event horizon, time stops. True False

True

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. True False

True

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

True

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

True

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

True

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

True

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

True

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. True False

True

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

True

The life ending event for a very massive star can result in long duration gamma-ray bursts. True False

True

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

True

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

True

The mass range for neutron stars is: a) 1.4 to 3 solar masses. b) .08 to .4 solar masses. c) 3 to 8 solar masses. d) .4 to 3 solar masses. e) 6 to 11 solar masses.

a) 1.4 to 3 solar masses.

What process is responsible for producing the rapid spin rate of millisecond pulsars? a) Gas spiraling in from a nearby companion transfers angular momentum to the pulsar, increasing the rate of its rotation. b) Recurrent novae begin to flash faster and faster as they consume more and more energy and material from their companion stars. c) Supernova blasts leave behind a rotating core that continues to spin faster as it collapses. d) Jets of energy emerging from the sides of the rotating neutron star cause it to spin faster and faster. e) Gravity from a nearby black hole pulls the neutron star into an increasingly tight spiral.

a) Gas spiraling in from a nearby companion transfers angular momentum to the pulsar, increasing the rate of its rotation.

What will happen to an isolated neutron star that accumulates more than about 3 solar masses of material? a) Gravity will overcome the neutron degeneracy in its interior and form a black hole. b) It will begin to flash on and off as a pulsar. c) It will explode in a Type II supernova. d)It will explode in a Type I supernova. e) It will split up into several smaller neutron stars.

a) Gravity will overcome the neutron degeneracy in its interior and form a black hole.

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 grow larger, temporarily becoming a red giant again. c) All of its protons and electrons would turn into quarks. e) It would erupt as a Type I supernova.

a) It could eventually become a black hole, via a hypernova explosion.

Why is light increasingly redshifted near a black hole? a) It must expend energy to escape the gravitational pull of the black hole. b) It is moving away from us very quickly as it is sucked into the black hole. c) It is moving increasingly fast in order to escape the pull of the black hole. d) Time is moving increasingly slowly in the light's frame of reference.

a) It must expend energy to escape the gravitational pull of the black hole.

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.

a) a black hole.

Three terrestrial-sized planets in orbits of a fraction of an AU have been found near: a) a millisecond pulsar. b) Supernova 1987A. c) a magnetar. d) a white dwarf. e) Cygnus X-1.

a) a millisecond pulsar.

What have astronomers detected in the center of the Crab Nebula? a) a neutron star b) a white dwarf c) a black hole d) a protostar e) None of these is correct.

a) a neutron star

The average density of neutron stars approaches: a) about 10^17 kg/m3, similar to the density of atomic nuclei. b) a million times that of normal matter. c) a million times that of even a white dwarf. d) about 10^18 times that of water. e) infinity.

a) about 10^17 kg/m3, similar to the density of atomic nuclei.

Redshift measurements of the visible afterglow of a gamma-ray burst show that these objects are: a) billions of light-years away. b) in the solar neighborhood. c) in the Local Group. d) at the most extreme observable distances. e) in the Milky Way Galaxy.

a) billions of light-years away.

What effect predicted by Einstein's theory of general relativity is confirmed during a solar eclipse? a) deflection of light from distant stars by the gravitational field of the Sun b) capture of distant starlight within the Sun's event horizon c) the Doppler shift of the Sun caused by its gravitational interaction with Jupiter d) creation of proton-antiproton pairs in the solar corona e) interaction of the solar wind with Earth's Van Allen belts

a) deflection of light from distant stars by the gravitational field of the Sun

Which of the following is NOT a property of a pulsar? a) emissions only in the visible part of the spectrum b) each pulse consisting of a 0.01 second burst of radiation c) period of 1.34 seconds d) time interval between pulses is very uniform e) over time, the period is gradually increasing

a) emissions only in the visible part of the spectrum

Two important properties of young neutron stars are: a) extremely rapid rotation and a strong magnetic field. b) no rotation and a weak magnetic field. c) extremely slow rotation and a strong magnetic field. d) no rotation and no magnetic field. e) extremely rapid rotation and a weak magnetic field.

a) extremely rapid rotation and a strong magnetic field.

In contrasting the distribution of the X-ray and gamma-ray bursts, we find: a) gamma ray bursts are far beyond our Galaxy, at cosmological distances, and spread all over the sky, not in the plane of our Galaxy. b) gamma ray bursts can repeat, while the X-ray bursts do not. c) gamma ray bursts are more closely associated with open than globular clusters. d) gamma ray bursts are far closer to us, so they appear more luminous. e) gamma ray bursts can be observed from the ground, but X-rays are blocked by the ionosphere for ground based observers.

a) gamma ray bursts are far beyond our Galaxy, at cosmological distances, and spread all over the sky, not in the plane of our Galaxy.

The densely packed neutrons of a neutron star cannot balance the inward pull of gravity if the total mass is: a) greater than Schwartzschild's limit of 3 solar masses. b) less than 1.0 solar masses. c) between 1.4 and 2.0 solar masses. d) Chandrasekhar's limit of 1.4 solar masses. e) greater than 25 solar masses.

a) greater than Schwartzschild's limit of 3 solar masses.

Short duration gamma-ray bursts are thought to be caused by: a) mergers of neutron stars and/or black holes. b) supernovae. c) mergers of white dwarfs. d) hypernovae. e) novae.

a) mergers of neutron stars and/or black holes.

To which of these phenomena are X-ray busters most similar? a) novae b) planetary nebulae c) hypernovae d) type I supernovae e) type II supernovae

a) novae

You would expect millisecond pulsars to be: a) part of a binary system. b) collapsing rapidly. c) most common in open clusters. d) rotating slowly. e) isolated in space.

a) part of a binary system.

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) shorter than when they are at rest. b) the same length as when they are at rest. c) wider than when they are at rest. d) narrower than when they are at rest. e) longer than when they are at rest.

a) shorter than when they are at rest.

Pulsars: a) spin very rapidly when they're young. b) emit radio in all directions. c) generally form from 25 solar mass stars. d) spin very slowly when they're young, and gradually spin faster as they age. e) are the cause of gamma-ray bursts.

a) spin very rapidly when they're young.

A critical difference between millisecond and normal pulsars is that: a) the millisecond ones are speeding up, but normal pulsars slow down over time. b) millisecond ones are only found in globular clusters, while normal ones are not. c) the millisecond ones all have planets, while normal ones do not. d) the millisecond ones are not associated with the galaxy, but scattered everywhere. e) the millisecond ones must eventually collapse into black holes.

a) the millisecond ones are speeding up, but normal pulsars slow down over time.

What defines the event horizon of a black hole? a) the radius at which the escape speed equals the speed of light b) the point of maximum gravity c) the point at which shockwaves emanate from the strong gravitational distortion the black hole creates in the fabric of spacetime d) the radius of the original neutron star before it became a black hole

a) the radius at which the escape speed equals the speed of light

If the Sun were replaced by a 1-solar-mass black hole, what would be the gravitational pull of the black-hole "Sun" on Earth? a) the same b) much greater c) much less d) There is not enough information to answer.

a) the same

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

a)if the beam sweeps across us, we will detect a pulse of radiation.

The Schwartzschild radius for a 12 solar mass star is: a) 100 km. b) 36 km. c) 4 km. d) 15 km. e) 3000 km.

b) 36 km.

In binary neutron star systems, the orbits are expected to slowly decay, eventually resulting in a merger of the neutron stars. Where does the orbital energy go? a) It is emitted as neutrinos. b) It is emitted as gravity waves. c) It is lost to friction. d) It is emitted as gamma-rays. e) It is converted to mass.

b) It is emitted as gravity waves.

What makes the Crab Nebula supernova remnant unusual as a supernova remnant? a) It is the nearest supernova remnant. b) It is the remnant of a supernova observed by humans. c) It is the biggest supernova remnant visible. d) It is the remnant of a supernova that was observed in the 20th century. e) It is the oldest supernova remnant known.

b) It is the remnant of a supernova observed by humans.

At what stage of its life will our Sun become a black hole? a) right after its main-sequence life b) The Sun will never become a black hole. c) right after it gives off a planetary nebula d) right after its red-giant stage e) right after it explodes as a supernova

b) The Sun will never become a black hole. (not massive enough)

What do the observed locations of gamma-ray bursts tell us about them? a) Astronomers cannot make any statements about their locations because they are completely random. b) They must be extra-galactic because they occur everywhere in the sky. c) They must originate in our Galaxy because they occur predominantly along the galactic plane. d) They must originate in our solar system because they occur predominantly along the ecliptic.

b) They must be extra-galactic because they occur everywhere in the sky.

Which of the following is NOT a reason that observable pulsars are found at the centers of some, but not all, supernova remnants? a) Type I binary-induced supernovae do not leave behind rotating neutron stars. b) Type II core-collapse supernovae do not leave behind rotating neutron stars. c) The radiation responsible for a typical pulsar "blip" leaves the neutron star in narrow beams, which we can detect only if they cross our line of sight. d) Pulsars spin down and become too faint to observe after several tens of millions of years. e)All of these statements are reasons.

b) Type II core-collapse supernovae do not leave behind rotating neutron stars.

A neutron star is about the same size as a) a school bus. b) a U.S. city. c) the Moon. d) Earth.

b) a U.S. city.

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.

b) a person in space, far from any gravitational source accelerating at g.

The supernova of 1054 AD produced: a) the closest known neutron star to our Sun. b) a pulsar with a period of 33 milliseconds, visible optically. c) a remnant still visible to the naked eye, the Crab Nebula, M-1. d) the most famous black hole. e) no remaining visible trace, as it was a type I supernova.

b) a pulsar with a period of 33 milliseconds, visible optically.

Most pulsars have a measured mass of: a) between 2 and 4 solar masses. b) about 1.4 solar masses. c) 5.2 solar masses. d) greater than 10 solar masses. e) less than 1.0 solar masses.

b) about 1.4 solar masses.

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) 1.5c. b) c. c) 2.5c. d) 0.25c. e) 0.5c.

b) c.

Almost half of all known millisecond pulsars are found in what type of object? a) giant molecular clouds b) globular clusters c) supernova remnants d) open clusters e) emission nebulae

b) globular clusters

As an object falls into a black hole, it: a) passes the event horizon intact. b) is broken up and heated before it reaches the event horizon. c) falls into a stable orbit around the black hole. d) passes into a location somewhere else. e) can emit high energy (gamma-ray) electromagnetic radiation that can leave the black hole.

b) is broken up and heated before it reaches the event horizon.

A method for identifying a black hole is to: a) search for radio waves from the accretion disk. 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 their pulsar signal. e) look for voids in the star fields.

b) look for their effects on nearby companions.

In a neutron star, the core is: a) constantly expanding and contracting. b) made of compressed neutrons in contact with each other. c) primarily iron and silicon. d) no longer rotating. e) electrons and protons packed so tightly they are in contact.

b) made of compressed neutrons in contact with each other.

An object more massive than the Sun, but roughly the size of a city, is a: a) supernova remnant. b) neutron star. c) brown dwarf. d) red dwarf. e) white dwarf.

b) neutron star.

X-ray bursters are caused by a process similar to the process in which other object? a) Type I supernova b) nova c) Type II supernova d) None of the above is correct.

b) nova

The best evidence for supermassive black holes in the centers of galaxies is a) unknown visible and X-ray spectral lines. b) rapid gas motion and intense energy emission. c) gravitational redshift of radiation emitted from near the center. d) the absence of stars there.

b) rapid gas motion and intense energy emission

A spacecraft moving near the speed of light will appear ________ compared to its appearance at rest. a) narrowed b) shortened c) widened d) lengthened e) unchanged

b) shortened

The most rapidly "blinking" pulsars are those that a) are hottest. b) spin fastest. c) are oldest. d) are most massive.

b) spin fastest

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 Hubble Space Telescope. c) the Chandra X-ray observatory. d) the Keck Telescopes used as an interferometer. e) the Spitzer Infrared Space Telescope.

b) the Hubble Space Telescope.

LIGO detected gravitational waves that probably originated from: a) dark matter falling into a black hole. b) the merger of two black holes. c) the merger of two white dwarfs. d) a supermassive black hole absorbing a nearby star. e) the merger of a black hole with a companion star.

b) the merger of two black holes.

The key to identifying a black hole candidate in a binary system is that: a) the unseen star is a contact binary. one of the two stars cannot be seen. b) the unseen companion in the system must have a sufficiently high mass. c) the visible companion must be an evolving main sequence or giant star. d) the system must be a very strong source of radio emissions.

b) the unseen companion in the system must have a sufficiently high mass.

As a spaceship nears an event horizon, a clock on the spaceship will be observed: a) to run faster. b) to run slowly. c) to stop. d) to run the same as one on Earth. e) to run backwards.

b) to run slowly.

The orbit of a close binary system involving two neutron stars gradually shrinks in radius. What happens to the orbital energy? a) It increases, with the source of energy coming from the beams that come from the pulsar stage of the neutron stars. b) It decreases, with the excess energy emitted as neutrinos. c) It decreases, with the excess energy emitted as gravitational waves. d) It decreases, with the excess energy increasing the temperatures of the neutron stars. e) It increases, with the source of energy coming from a decrease in the temperatures of the neutron stars.

c) It decreases, with the excess energy emitted as gravitational waves.

Whose work with SETI led to the discovery of pulsars in 1967? a) Stephen Hawking b) Martin Schwarzschild c) Jocelyn Bell d) Anthony Hewish e) Sir Bernard Lovell

c) Jocelyn Bell

General relativity explains the observed precession of the orbit of: a) Io. b) Earth. c) Mercury. d) Jupiter. e) Pluto.

c) Mercury.

What compelling evidence links pulsars to neutron stars? a) Pulsars are known to evolve into neutron stars. b) Both pulsars and neutron stars can be found in globular star clusters. 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.

c) Only a small, very dense source could rotate that rapidly without flying apart.

Why aren't all young neutron stars seen as pulsars? a) Many neutron stars do not emit beams of radiation. b) Most neutron stars are too distant to be observed as pulsars. c) Only some neutron stars are oriented so that their beams sweep in the direction of Earth. d) Some neutron stars don't rotate.

c) Only some neutron stars are oriented so that their beams sweep in the direction of Earth.

What would happen if mass is added to a 1.4 solar mass white dwarf? a) The core would collapse as a type II supernova. b) The star's radius would increase. c) The star would erupt as a carbon detonation (type I) supernova. d) The star would explode as a nova. e) The star would immediately collapse into a black hole.

c) The star would erupt as a carbon detonation (type I) supernova.

If light from a distant star passes close to a massive body, the light beam will: a) slow down. b) continue moving in a straight line. c) bend towards the star due to gravity. d) accelerate due to gravity. e) change color to a shorter wavelength.

c) bend towards the star due to gravity.

If we were to use a telescope and a black hole passes between our line of sight and a star, we would see the image of the star in the telescope: a) remain constant because the diameter of the black hole is so small compared to the star. b) darken because the black hole would block some or all of the light. c) blur because the black hole would gravitationally deflect the light. d) sharpen because the black hole would gravitationally deflect the light.

c) blur because the black hole would gravitationally deflect the light.

What keeps light (and all other forms of radiation) from escaping a black hole? a) the event horizon, which is an opaque solid surface b) the photon sphere, which reflects all radiation c) gravity d) very strong magnetic fields

c) gravity

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 increase and its clock will run faster. c) its length will decrease and its clock will run more slowly. d) its length will decrease and its clock will run faster. e) None of these will happen.

c) its length will decrease and its clock will run more slowly.

A neutron star's immense gravitational attraction is due primarily to its small radius and a) strong magnetic field. b) high temperature. c) large mass. d) rapid rotation rate.

c) large mass.

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.

c) lie in the cores of the most massive galaxies.

If the Sun were replaced by a one solar mass black hole: a) the Earth would immediately escape into deep space, driven out by its radiation. b) all terrestrial planets would fall in immediately. c) the Earth would still orbit it in a period of one year. d) life on Earth would be unchanged. e) clocks on Earth would all stop.

c) the Earth would still orbit it in a period of one year

Which of the following is NOT an observational feature associated with the binary-star system Cygnus X-1, which is suspected of containing a black hole? a) Its visible companion star, if on the main sequence, should have a mass about 25 times that of the Sun. b) X-ray emission from this region suggests the presence of a high-temperature gas. c) Spectroscopic observations of visible light show that the binary-star system has an orbital period of less than 6 days. d) A small, dark region in the space near the visible companion indicates that light cannot escape from that region, which is the characteristic feature of a black hole. e) Rapid time variations in the X-ray radiation of Cygnus X-1 imply that the X-ray-emitting region is a few hundred kilometers across.

d) A small, dark region in the space near the visible companion indicates that light cannot escape from that region, which is the characteristic feature of a black hole.

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.

d) Both A and B are possible.

What explanation does general relativity provide for gravity? a) Gravity is inversely proportion to the radius of the body. b) Gravity can affect only massive particles, not massless photons. c) Gravity is directly proportional to the mass of the attracting body. d) Gravity is the result of curved spacetime. e) Gravity is the opposite of the electromagnetic force.

d) Gravity is the result of curved spacetime.

What makes the Crab pulsar somewhat unusual among pulsars in general? a) It is the fastest pulsar known. b) It is the oldest pulsar observed. c) It is the most intense source of X-rays in the sky. d) It is rather bright at visible wavelengths. e) Its period is not regular like other pulsars.

d) It is rather bright at visible wavelengths.

What can we detect from matter that has crossed an event horizon? a) Gamma-ray bursts b) Visible light c) X-rays if the matter was dense d) Nothing e) Radio waves if the matter was traveling fast enough

d) Nothing

Which of the following is NOT an argument for Cygnus X-1's being a true black hole? a) X-rays from Cygnus X-1 vary on time scales as short as a millisecond. b) Spectroscopic data suggests hot gas is flowing from the companion B star onto Cygnus X-1. c) X-ray observations around the object support a temperature of several million K. d) The mass of the visible B star is even greater than Cygnus X-1, at around 25 solar masses. e) Cygnus X-1's mass is estimated to be about 10 solar masses.

d) The mass of the visible B star is even greater than Cygnus X-1, at around 25 solar masses.

Why does the existence of planets around a millisecond pulsar come as a surprise? a) Theory predicts that planets should have spiraled into the pulsar long ago. b) The pulsar should have evaporated the planets many years ago. c) The pulsar's magnetic field should have thrown the planets out of their orbits long ago. d) The supernova explosion that formed the pulsar would have blown away any planets originally there.

d) The supernova explosion that formed the pulsar would have blown away any planets originally there.

Which of these does NOT exist? a) a 6 solar mass black hole b) a 1.0 solar mass white dwarf c) a million solar mass black hole d) a 6.8 solar mass neutron star e) a 0.06 solar mass brown dwarf

d) a 6.8 solar mass neutron star

If light from a distant star passes close to a massive body, the light beam will: a) change color to a shorter wavelength. b) accelerate due to gravity. c) slow down. d) bend towards the star due to gravity. e) continue moving in a straight line.

d) bend towards the star due to gravity.

The best place to search for black holes is in a region of space that a) is cooler than its surroundings. b) has recently lost some stars. c)is dark and empty. d) has strong X-ray emission.

d) has strong X-ray emission.

Relatively long duration gamma-ray bursts are produced by: a) supernovae. b) novae. c) black hole mergers. d) hypernovae. e) neutron star mergers.

d) hypernovae.

In the Lighthouse model: a) pulsars are navigational devices created by interstellar navigators as discovered by Jocelyn Bell in 1967. b) all pulsars have their poles pointed directly at us or they would be not observable. c) the period of pulsation must speed up as the neutron star continues contracting. d) if the beams sweeps across us, we can observe the pulse. e) pulsars are observable only if they lie in the galactic plane.

d) if the beams sweeps across us, we can observe the pulse.

Black holes result from stars having initial masses a) less than the mass of the Sun. b) between 1 and 2 times the mass of the Sun. c) up to 8 times the mass of the Sun. d) more than 25 times the mass of the Sun.

d) more than 25 times the mass of the Sun.

To an observer on Earth, the clock on a spaceship moving at constant, but high velocity, would: a) go backwards. b) stop. c) run fast. d) run slow.

d) run slow.

Neutron stars are formed by: a) mass transfer in binary star systems. b) the star formation process. c) novae. d) type II supernovae. e) type I supernovae.

d) type II supernovae.

Neutron stars have: a) weak or non-existent magnetic fields. b) periods of days or weeks. c) monopolar fields that switch polarity every rotation. d) very strong bi-polar magnetic fields. e) no relation to pulsars.

d) very strong bi-polar magnetic fields.

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

e) All of the above

Which of the following are attracted by gravity? a) neutrinos b) antimatter c) any object with mass d) electromagnetic radiation e) All of the above

e) All of the above

The observed slowing of a clock in the vicinity of a black hole is a prediction of: a) Special relativity. b) the Roche Limit. c) Stellar nucleosynthesis. d) the Cosmological Principle. e) General relativity.

e) General relativity.

Why do scientists describe the theory of gravity as "incomplete"? a) It does not explain the effects on time from a massive object. b) It does not agree with the expansion of the universe. c) The gravitational waves it predicts have not been observed. d) It does not explain why light bends near a dense object. e) It does not incorporate a description of matter on a very small scale.

e) It does not incorporate a description of matter on a very small scale.

Which of the following can actually escape from inside a black hole's event horizon? a) gravitons b) electrons c) neutrinos d) very high energy gamma-rays e) None of the above

e) None of the above

What are X-ray bursters? a) They are very massive stars that explode as supernovae, emitting bursts of X- rays and gamma-rays in the process. b) They are the central sources of energy for planetary nebulae. 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.

e) They are neutron stars on which accreted matter builds up, then explodes in a violent nuclear explosion.

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 contact binary system of two red giants. b) two neutron stars in a mass transfer binary. c) a white dwarf and a neutron star. d) a white dwarf and a main sequence star. e) a main sequence or giant star and a neutron star in a mass transfer binary.

e) a main sequence or giant star and a neutron star in a mass transfer binary.

Which of the following is NOT a characteristic feature of a neutron star? a) some of the highest densities possible b) a mass much greater than the Sun's. c) a powerful magnetic field d) very rapid rotation e) a radius about the size of the Earth's

e) a radius about the size of the Earth's

The vast majority of pulsars are known only from their pulses in: a) visible light. b) microwaves. c) X-rays. d) gamma-rays. e) radio waves.

e) radio waves.

Neutron stars do NOT have: a) large surface gravities, compared to the Sun. b) sizes comparable to large cities. c) masses greater than 1.4 solar masses. d) strong magnetic fields. e) rotation periods comparable to the Sun's.

e) rotation periods comparable to the Sun's.

What is Cygnus X-1? a) the brightest star in the constellation Cygnus b) the first gamma-ray burster to be spotted in other wavelengths as well c) the strongest X-ray eclipsing binary system in the sky d) a millisecond pulsar with three Earth-like planets around it e) the leading candidate for an observable black hole binary system

e) the leading candidate for an observable black hole binary system

According to the special theory of relativity, as the speed of a rocket ship increases, an observer sees the mass of a spaceship: a) increase. b) stay the same. c) fluctuate. d) decrease. e) converted to energy.

increase.