Multiple-Choice Questions
1) 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.
Page Ref: 13.1
2) 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.
Page Ref: 13.1
3) 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.
Page Ref: 13.1
4) The mass range for neutron stars is
A) .08 to .4 solar masses.
B) .4 to 3 solar masses.
C) 1.4 to 3 solar masses.
D) 3 to 8 solar masses.
E) 6 to 11 solar masses.
Page Ref: 13.1
5) Which of these does not exist?
A) a million solar mass black hole
B) a 6 solar mass black hole
C) a 1.8 solar mass neutron star
D) a 1.5 solar mass white dwarf
E) a 0.06 solar mass brown dwarf
Page Ref: 13.1
6) Most pulsars are observed only as ________ sources.
A) gamma-ray burster
B) visible lighthouse
C) ultraviolet repeating
D) radio
E) x-ray
Page Ref: 13.2
7) 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.
Page Ref: 13.2
8) What makes the Crab Nebula pulsar unusual among other pulsars?
A) It is the fastest spinning known pulsar.
B) It is a magnetar, with far more intense magnetic fields than any other.
C) It is relatively bright in shorter wavelengths, like visible and X-rays.
D) Its period is much less regular than other pulsars.
E) It is the oldest known pulsar.
Page Ref: 13.2
9) Who discovered the first four pulsars?
A) Anthony Hewish
B) Stephen Hawking
C) Carl Sagan
D) Jocelyn Bell
E) Martin Schwartzschild
Page Ref: 13.2
10) 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 radio in all directions.
Page Ref: 13.2
11) 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.
Page Ref: 13.2
12) 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.
Page Ref: 13.2
13) The supernova of 1054 produced
A) a supernova remnant still visible to the naked eye.
B) an optically visible pulsar with a period of 33 milliseconds.
C) the most famous black hole, Cygnus X-1.
D) the first known gamma-ray burster.
E) no remaining trace, like most Type I supernovae.
Page Ref: 13.2
14) 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.
Page Ref: 13.3
15) Many of the millisecond pulsars lie in ________, suggesting great stellar density.
A) emission nebulae
B) planetary nebulae
C) globular clusters
D) open clusters
E) giant molecular clouds
Page Ref: 13.3
16) X-ray bursters occur in binary systems, containing a
A) white dwarf and a neutron star.
B) pair of white dwarfs.
C) red giant and a neutron star.
D) pair of neutron stars.
E) black hole and a main sequence star.
Page Ref: 13.3
17) 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.
Page Ref: 13.3
18) 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.
Page Ref: 13.3
19) 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.
Page Ref: 13.4
20) 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.
Page Ref: 13.4
21) In a hypernova, a very energetic supernova creates a
A) very visible supernova remnant.
B) millisecond pulsar.
C) set of planets to orbit their neutron star host.
D) black hole.
E) white dwarf and its planetary nebula.
Page Ref: 13.4
22) 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.
Page Ref: 13.4
23) Which statement about gamma ray bursters is not correct?
A) They seem to be coming from far beyond our own Milky Way.
B) They are scaled up X-ray bursters, with more massive objects involved.
C) In seconds, they radiate hundreds of times more energy than even supernovae do.
D) Millisecond flickering implies they are tiny in size.
E) The beams may be bi-polar ejections from the hypernova formation of black holes.
Page Ref: 13.4
24) Which are the two most popular candidates for gamma-ray bursters?
A) hypernova making pulsars, and mergers of two white dwarfs
B) mergers of two black holes, and merger of a neutron star and a white dwarf
C) hypernova making a black hole, and merger of two neutron stars
D) collisions between a white dwarf and a giant, and merger of two neutron stars
E) formation of uranium in the core of a supergiant, and collisions of white dwarfs
Page Ref: 13.4
25) Which statement about black holes is true?
A) Their escape velocity is greater than the speed of light.
B) They form from 1.4 solar mass stars.
C) They form an event horizon at twice the Schwartzschild radius.
D) Their main sequence mass was 5-10 solar masses.
E) Their event horizon is a physical surface boundary.
Page Ref: 13.5
26) 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) not at least 25 solar masses.
Page Ref: 13.5
27) 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
Page Ref: 13.5
28) 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.
Page Ref: 13.6
29) 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
Page Ref: 13.6
30) 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.
Page Ref: 13.6
31) 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.
Page Ref: 13.6
32) What can we detect from matter that has crossed an event horizon?
A) Gamma bursts.
B) Radio waves if the matter was traveling fast enough.
C) Visible light.
D) X-rays if the matter was dense.
E) Nothing.
Page Ref: 13.7
33) 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.
Page Ref: 13.7
34) 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.
Page Ref: 13.7
35) 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
Page Ref: 13.8
36) 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.
Page Ref: 13.8
37) 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.
Page Ref: 13.8
38) 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) Spectroscopic data suggests hot gas is flowing toward the X-ray source.
C) The mass of the visible star is greater than that of the X-ray source.
D) The mass of the X-ray source is about 10 solar masses.
E) The X-rays from the compact source vary in as little as a millisecond.
Page Ref: 13.8