Question 1

What is it that keeps a white dwarf from collapsing inward on itself?

Accepted Answer

A)   electron degeneracy, or "quantum crowding"
B)   the physical size of the neutrons of which this star is composed
C)   convection currents, or updrafts, from the nuclear furnace
D)   normal gas pressure

Question 2

In studying the magnetic fields of planets,we have found that rotation was a requirement for an object to produce a magnetic field.It is not surprising then that,when a massive star collapses:

Accepted Answer

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

Question 3

Why do we 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 became joined.
C)   Magnetars are superconducting throughout.
D)   Magnetars have a higher proportion of protons and thus have stronger electric currents.

Question 4

The star Sirius (α Canis Majoris) is actually a binary star in which the brighter,more massive star (Sirius A) is an A-type main-sequence star and the fainter,less massive star (Sirius B) is a white dwarf.How is this system MOST likely to have formed?

Accepted Answer

A)   Sirius A formed as a single star and later captured a passing white dwarf.
B)   Sirius B formed first and evolved to become a white dwarf; capture of gas and dust from interstellar clouds then resulted in the formation of Sirius A.
C)   Sirius B was initially more massive than Sirius A and evolved faster; it then became less massive due to mass loss to space and mass transfer to Sirius A.
D)   Sirius A was always the more massive of the two and became a red giant; then mass transfer to Sirius B accelerated the evolution of Sirius B and caused it to become a white dwarf.

Question 5

What is believed to be the maximum mass for a neutron star?

Accepted Answer

A)   150 solar masses
B)   12 solar masses
C)   1.4 solar mass
D)   3 solar masses

Question 6

What are the main products of helium nuclear fusion in red giant stars?

Accepted Answer

A)   hydrogen nuclei by nuclear fission
B)   energy from the complete transformation of the mass of helium to energy
C)   iron nuclei
D)   carbon and oxygen nuclei

Question 7

The difference between a Schwarzschild black hole (SBH) and a Kerr black hole (KBH) is:

Accepted Answer

A)   overall mass; an SBH contains about 20 solar masses, whereas a KBH is greater than 20 solar masses.
B)   that the KBH is electrically charged whereas the SBH is not.
C)   that an SBH is spinning, whereas a KBH is not.
D)   that a KBH is spinning, whereas an SBH is not.

Question 8

Black holes do not possess a magnetic field because:

Accepted Answer

A)   the magnetic field is radiated away in the form of gravitational waves during the collapse.
B)   black holes cannot have electric charge, which is needed to create a magnetic field.
C)   magnetic fields are created by spinning charges, and black holes cannot spin.
D)   an object with a magnetic field cannot collapse into a black hole.

Question 9

What is the ergoregion of a Kerr black hole?

Accepted Answer

A)   a region outside the event horizon where objects cannot remain at rest without falling into the black hole
B)   a region inside the event horizon where virtual particles are created from the vacuum of space
C)   the inner part of the accretion disk, where X-rays are generated
D)   a region between the event horizon and the singularity from which nothing can escape

Question 10

In general,how many fundamentally different types of black holes are expected to exist?

Accepted Answer

A)   only one-in which all properties but mass are destroyed when a black hole is created
B)   two-those that have electric charge and those that have no electric charge
C)   three-atomic-mass black holes, stellar-mass black holes, and supermassive black holes
D)   two-those that rotate and those that do not rotate

Question 11

From the start of collapse to the attainment of nuclear density,the process of core collapse at the end of the life of a massive star takes about:

Accepted Answer

A)   1/2000 second.
B)   8 minutes.
C)   a few hours.
D)   1/4 second.

Question 12

A white dwarf,the surviving core of a low-mass star toward the end of its life,can be found on the Hertzsprung-Russell diagram:

Accepted Answer

A)   at the upper-left end of the main sequence since its surface temperature is extremely high.
B)   at the bottom end of the main sequence, along which it has evolved throughout its life.
C)   below and to the left of the main sequence.
D)   above and to the right of the main sequence since it evolved there after its hydrogen-fusion phase.

Question 13

Do neutron stars have atmospheres?

Accepted Answer

A)   No. The gravitational pull is too great to allow anything to exist above the surface.
B)   Yes, but the "atmosphere" consists of loosely bound neutrons circling the star.
C)   Yes. Bright emission-line spectra have been observed.
D)   Yes. Dark absorption-line spectra have been observed.

Question 14

A stellar core of about 2 solar masses collapses inward in a supernova explosion.What is the result of this collapse?

Accepted Answer

A)   a neutron star supported from further collapse by neutron-degeneracy pressure
B)   a black hole with infinitely small radius since nothing can prevent such a mass from collapsing completely
C)   a star a little smaller than the size of the Sun supported from further collapse by gas pressure from the hot interior of the star
D)   a white dwarf supported from further collapse by degenerate-electron pressure

Question 15

The pulsed nature of the radiation at all wavelengths that is seen to come from a pulsar is produced by:

Accepted Answer

A)   the rapid pulsation in size and brightness of a small white dwarf.
B)   the rapid rotation of a neutron star that is producing two oppositely directed beams of radiation.
C)   the mutual eclipses of two very hot stars orbiting in a close binary system.
D)   extremely hot matter that is rapidly orbiting a black hole just prior to descending into it.

Question 16

The event that follows the asymptotic giant branch (AGB) phase in the life of a low-mass star is:

Accepted Answer

A)   the ejection of a planetary nebula.
B)   core collapse and a supernova explosion.
C)   helium flash and the start of helium fusion in the core.
D)   the onset of hydrogen fusion in the core.

Question 17

The stars that eventually become white dwarfs start life with solar masses less than:

Accepted Answer

A)   25.
B)   8.
C)   1.4.
D)   3.

Question 18

The interiors of white dwarfs are characteristically:

Accepted Answer

A)   mainly carbon and oxygen nuclei supported by electron degeneracy pressure in a volume about the size of the Sun.
B)   mostly hydrogen nuclei supported by normal gas pressure due to the very high gas temperature, in a volume about the size of the Earth.
C)   mainly carbon and oxygen nuclei supported by electron degeneracy pressure in a volume about the size of the Earth.
D)   mainly helium nuclei supported by electron degeneracy pressure in a volume with a radius about 11 times that of the Earth, about the volume of Jupiter.

Question 19

You are going to make measurements of the following entities.For which one will Newtonian physics give you answers that are precise enough for practical use?

Accepted Answer

A)   the advance of the perihelion of the orbit of Mercury
B)   the orbit of a satellite around Earth
C)   two neutron stars orbiting each other
D)   GPS locations on Earth from orbiting satellites

Question 20

What name is given to a rotating black hole?

Accepted Answer

A)   Schwarzschild black hole
B)   Hawking singularity
C)   wormhole
D)   Kerr black hole

Exam 12: The Deaths and Remnants of Stars

What are the main products of helium nuclear fusion in red giant stars?

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Black holes do not possess a magnetic field because:

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The difference between a Schwarzschild black hole (SBH) and a Kerr black hole (KBH) is:

Correct AnswerverifiedShow Answer

The interiors of white dwarfs are characteristically:

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

What name is given to a rotating black hole?

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You are going to make measurements of the following entities.For which one will Newtonian physics give you answers that are precise enough for practical use?

Correct AnswerverifiedShow Answer

The pulsed nature of the radiation at all wavelengths that is seen to come from a pulsar is produced by:

Correct AnswerverifiedShow Answer

In general,how many fundamentally different types of black holes are expected to exist?

Correct AnswerverifiedShow Answer

From the start of collapse to the attainment of nuclear density,the process of core collapse at the end of the life of a massive star takes about:

Correct AnswerverifiedShow Answer

A stellar core of about 2 solar masses collapses inward in a supernova explosion.What is the result of this collapse?

Correct AnswerverifiedShow Answer

A white dwarf,the surviving core of a low-mass star toward the end of its life,can be found on the Hertzsprung-Russell diagram:

Correct AnswerverifiedShow Answer

Do neutron stars have atmospheres?

Correct AnswerverifiedShow Answer

What is it that keeps a white dwarf from collapsing inward on itself?

Correct AnswerverifiedShow Answer

The stars that eventually become white dwarfs start life with solar masses less than:

Correct AnswerverifiedShow Answer

In studying the magnetic fields of planets,we have found that rotation was a requirement for an object to produce a magnetic field.It is not surprising then that,when a massive star collapses:

Correct AnswerverifiedShow Answer

The event that follows the asymptotic giant branch (AGB) phase in the life of a low-mass star is:

Correct AnswerverifiedShow Answer

What is the ergoregion of a Kerr black hole?

Correct AnswerverifiedShow Answer

What is believed to be the maximum mass for a neutron star?

Correct AnswerverifiedShow Answer

The star Sirius (α Canis Majoris) is actually a binary star in which the brighter,more massive star (Sirius A) is an A-type main-sequence star and the fainter,less massive star (Sirius B) is a white dwarf.How is this system MOST likely to have formed?

Correct AnswerverifiedShow Answer

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