Question 1

The interior of a neutron star is believed to contain

Accepted Answer

A)   neutrons compressed into a crystalline lattice structure by very high pressure.
B)   a dense gas consisting mostly of neutrons.
C)   a metallic fluid of almost pure iron.
D)   neutrons in a superfluid state.E) A) and D)
F) All of the above

Question 2

Which one of these phenomena is NOT associated with a rotating neutron star?

Accepted Answer

A)   magnetar
B)   soft gamma-ray repeater
C)   rotating radio transient
D)   weakly interacting massive particlesE) A) and C)
F) A) and D)

Question 3

The end states of low-mass stars differ dramatically from high-mass stars. In this context, what is the boundary between these two classifications?

Accepted Answer

A)   0.4 MSun
B)   2.0 MSun
C)   8.0 MSun
D)   16.0 MSunE) B) and D)
F) C) and D)

Question 4

What will be the mass of the Sun at the end of its asymptotic giant branch (AGB)  phase, due to mass loss to space by its stellar wind?

Accepted Answer

A)   still almost 1 solar mass since mass loss is negligible for a low-mass star like the Sun
B)   between 0.1 and 0.2 solar mass
C)   about 0.8 solar mass
D)   about 0.5 solar massE) A) and B)
F) All of the above

Question 5

A planetary nebula is

Accepted Answer

A)   a shell of ejected gases.
B)   the formation stages of planets around stars.
C)   a gas cloud surrounding a planet after its formation.
D)   the spherical cloud of gas produced by a supernova explosion.E) B) and D)
F) A) and D)

Question 6

What happens to the outer layers of a low-mass star after the helium core and shell fusion stages are completed?

Accepted Answer

A)   The star stabilizes at the size of a red giant star, radiation pressure from below balancing gravity from the core, and slowly cools for the rest of its life.
B)   The outer layers are spun off into space to make a spiral structure known as a spiral galaxy.
C)   The outer layers are propelled slowly away from the core to form a planetary nebula.
D)   The star contracts back onto the core and becomes hot enough to undergo further hydrogen fusion, leading to a very hot and active, white dwarf star.E) None of the above
F) A) and C)

Question 7

Why do astronomers believe a magnetar can have a much stronger magnetic field than that of an ordinary neutron star?

Accepted Answer

A)   Magnetars were formed from supergiant stars many times larger than the stars that produced ordinary neutron stars.
B)   When first formed as neutron stars, magnetars were spinning rapidly enough that the magnetic fields produced by convection amplified the magnetic field of the original star.
C)   Magnetars are superconducting throughout.
D)   Magnetars have a higher proportion of protons and thus have stronger electric currents.E) All of the above
F) A) and C)

Question 8

Electron degeneracy occurs when the carbon core of a white dwarf becomes dense enough. Neutron degeneracy occurs when a neutron star becomes dense enough. Why is there no "proton degeneracy" in some density range between electron and neutron degeneracy?

Accepted Answer

A)   These degeneracies can occur only for neutral particles, and protons carry an electric charge.
B)   The pressure at which the electron degeneracy is overcome (so that the core collapses)  is also sufficient to combine electrons and protons to form neutrons. Thus, most protons disappear when the electron degeneracy ends.
C)   Protons are too large and heavy to exert degeneracy pressure. This concept applies only to smaller, lighter particles like electrons.
D)   Protons are not governed by the Pauli exclusion principle, as are electrons and neutrons.E) All of the above
F) A) and D)

Question 9

Near the end of its life a high-mass star has six active fusion shells surrounding its core. How many such shells did it have when it was on the main sequence?

Accepted Answer

A)   none
B)   one
C)   three
D)   sixE) None of the above
F) A) and B)

Question 10

Which force induces the core to contract inward and get hotter in massive stars at the conclusion of each episode of nuclear fusion, such as the carbon-, oxygen-, and silicon- fusion cycles?

Accepted Answer

A)   gravity
B)   gas pressure produced by the very high gas temperatures
C)   electron degeneracy pressure
D)   nuclear attractive force between nuclei and between neutrons and protonsE) A) and B)
F) A) and C)

Question 11

Supernovae have been detected

Accepted Answer

A)   in both the Milky Way Galaxy and other galaxies.
B)   only at X-ray wavelengths.
C)   only in elliptical galaxies, never in spirals.
D)   only in the Milky Way Galaxy.E) A) and B)
F) A) and C)

Question 12

What important event was recorded by ancient Chinese astronomers in A.D. 1054?

Accepted Answer

A)   brilliant worldwide auroral display
B)   appearance of a nearby nova explosion in the Milky Way Galaxy
C)   bright binary star undergoing eclipse
D)   appearance of a supernova in the Crab NebulaE) A) and B)
F) B) and C)

Question 13

A white dwarf star is supported from collapse under gravity by

Accepted Answer

A)   pressure of the gas heated by nuclear fusion reactions in its core.
B)   centrifugal force due to rapid rotation.
C)   degenerate-electron pressure in the compact interior.
D)   pressure of the gas heated by nuclear fusion reactions in a shell around its core.E) All of the above
F) C) and D)

Question 14

Which of these astronomical objects is MOST closely associated with a pulsar?

Accepted Answer

A)   red giant star
B)   neutron star
C)   black hole
D)   white dwarf starE) C) and D)
F) A) and B)

Question 15

The magnetic fields of planets demonstrate that rotation is a requirement for an object to produce a magnetic field. It is not surprising, then, that when a massive star collapses the rotation rate

Accepted Answer

A)   and the magnetic field strength both increase.
B)   increases but the magnetic field strength decreases.
C)   decreases but the magnetic field strength increases.
D)   and the magnetic field strength both decrease.E) C) and D)
F) A) and B)

Question 16

How did SN 1987A differ from most other observed supernovae?

Accepted Answer

A)   SN 1987A occurred in an external galaxy, not the Milky Way Galaxy.
B)   SN 1987A reached a maximum luminosity several times that of a normal supernova, because it exploded as a red supergiant.
C)   SN 1987A declined in brightness much faster than most supernovae.
D)   SN 1987A reached a maximum luminosity much later than a normal supernova, because it exploded as a blue supergiant.E) A) and C)
F) B) and C)

Question 17

Which of these is a method astronomers have recently used to study the structure of white dwarfs?

Accepted Answer

A)   measuring how their light curves vary with time to study pulsations of the stars
B)   measuring gravitational waves generated by pulsations of the stars
C)   measuring neutrinos released when a cool white dwarf crystallizes
D)   capturing material ejected by novae with spacecraftE) None of the above
F) B) and C)

Question 18

The core collapse phase at the end of the life of a massive star is triggered when

Accepted Answer

A)   the helium flash and thermal pulses have expelled the star's envelope.
B)   the density reaches the threshold for electron degeneracy pressure to become important.
C)   nuclear fusion has produced a significant amount of iron in its core.
D)   the core becomes as dense as an atomic nucleus.E) C) and D)
F) A) and B)

Question 19

The sequence of thermonuclear fusion processes inside massive stars can transform elements such as carbon and oxygen into heavier elements and generate excess energy until iron has been produced. Why is it NOT possible for fusion reactions to release energy from iron nuclei?

Accepted Answer

A)   The electrostatic charge of iron nuclei is so great that other nuclei cannot approach closely enough to react with them.
B)   Iron has the largest nucleus of all elements, and fusing other nuclei with iron actually reduces the size of the nucleus.
C)   Iron is the heaviest naturally occurring element.
D)   The protons and neutrons in an iron nucleus are so tightly bound together that fusing other nuclei with iron absorbs energy rather than releases it.E) A) and D)
F) B) and C)

Question 20

What is the origin of the rings of gas that surround SN 1987A?

Accepted Answer

A)   The rings were formed by stellar winds before the supernova erupted.
B)   These were caused by the gamma rays, which also caused photodisintegration.
C)   These rings were pushed out by the core bounce.
D)   The rings were formed when the shock wave lifted the outer layers of the star.E) B) and C)
F) A) and B)

Exam 14: The Death of Stars

The end states of low-mass stars differ dramatically from high-mass stars. In this context, what is the boundary between these two classifications?

Correct AnswerverifiedShow Answer

What important event was recorded by ancient Chinese astronomers in A.D. 1054?

Correct AnswerverifiedShow Answer

The sequence of thermonuclear fusion processes inside massive stars can transform elements such as carbon and oxygen into heavier elements and generate excess energy until iron has been produced. Why is it NOT possible for fusion reactions to release energy from iron nuclei?

Correct AnswerverifiedShow Answer

The interior of a neutron star is believed to contain

Correct AnswerverifiedShow Answer

Near the end of its life a high-mass star has six active fusion shells surrounding its core. How many such shells did it have when it was on the main sequence?

Correct AnswerverifiedShow Answer

A planetary nebula is

Correct AnswerverifiedShow Answer

Which of these is a method astronomers have recently used to study the structure of white dwarfs?

Correct AnswerverifiedShow Answer

What happens to the outer layers of a low-mass star after the helium core and shell fusion stages are completed?

Correct AnswerverifiedShow Answer

A white dwarf star is supported from collapse under gravity by

Correct AnswerverifiedShow Answer

The core collapse phase at the end of the life of a massive star is triggered when

Correct AnswerverifiedShow Answer

Which one of these phenomena is NOT associated with a rotating neutron star?

Correct AnswerverifiedShow Answer

Supernovae have been detected

Correct AnswerverifiedShow Answer

The magnetic fields of planets demonstrate that rotation is a requirement for an object to produce a magnetic field. It is not surprising, then, that when a massive star collapses the rotation rate

Correct AnswerverifiedShow Answer

What will be the mass of the Sun at the end of its asymptotic giant branch (AGB) phase, due to mass loss to space by its stellar wind?

Correct AnswerverifiedShow Answer

Electron degeneracy occurs when the carbon core of a white dwarf becomes dense enough. Neutron degeneracy occurs when a neutron star becomes dense enough. Why is there no "proton degeneracy" in some density range between electron and neutron degeneracy?

Correct AnswerverifiedShow Answer

Why do astronomers believe a magnetar can have a much stronger magnetic field than that of an ordinary neutron star?

Correct AnswerverifiedShow Answer

How did SN 1987A differ from most other observed supernovae?

Correct AnswerverifiedShow Answer

What is the origin of the rings of gas that surround SN 1987A?

Correct AnswerverifiedShow Answer

Which force induces the core to contract inward and get hotter in massive stars at the conclusion of each episode of nuclear fusion, such as the carbon-, oxygen-, and silicon- fusion cycles?

Correct AnswerverifiedShow Answer

Which of these astronomical objects is MOST closely associated with a pulsar?

Correct AnswerverifiedShow Answer

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