Question 1

How do magnetars form?

Accepted Answer

A)  from strong jets near supermassive black holes 
B)  from the merger of two neutron stars 
C)  from the brightest supernovae 
D)  from acceleration of cosmic rays in supernova remnants 
A)  from strong jets near supermassive black holes 
B)  from the merger of two neutron stars 
C)  from the brightest supernovae 
D)  from acceleration of cosmic rays in supernova remnants

Question 2

What is the origin of millisecond pulsars?

Accepted Answer

A)  As a pulsar cools, it collapses further. This causes its rotation rate to increase. 
B)  Pulsars in binary systems can draw mass from the binary companion. This mass, impacting the pulsar's surface, causes its rotation rate to increase. 
C)  The jets that radiate energy away from a pulsar cause it to become smaller and to rotate faster. 
D)  The rotation period for most pulsars is actually less than a millisecond. So, the natural slowing as it loses energy moves it into the millisecond range. 
A)  As a pulsar cools, it collapses further. This causes its rotation rate to increase. 
B)  Pulsars in binary systems can draw mass from the binary companion. This mass, impacting the pulsar's surface, causes its rotation rate to increase. 
C)  The jets that radiate energy away from a pulsar cause it to become smaller and to rotate faster. 
D)  The rotation period for most pulsars is actually less than a millisecond. So, the natural slowing as it loses energy moves it into the millisecond range.

Question 3

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. 
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 4

In astronomical terms, planetary nebulae are

Accepted Answer

A)  very long-lived objects, having been in existence since just after the Big Bang at the beginning of the universe. 
B)  relatively short-lived, existing around the central white dwarf star for millions of years before slowly spreading into space. 
C)  relatively long-lived since they form when the original stars form and remain as slowly rotating shells for the whole of their lifetimes of several billion years. 
D)  very short-lived, with lifetimes of about 20,000 years. 
A)  very long-lived objects, having been in existence since just after the Big Bang at the beginning of the universe. 
B)  relatively short-lived, existing around the central white dwarf star for millions of years before slowly spreading into space. 
C)  relatively long-lived since they form when the original stars form and remain as slowly rotating shells for the whole of their lifetimes of several billion years. 
D)  very short-lived, with lifetimes of about 20,000 years.

Question 5

A binary system is formed with a neutron star and another star that has overflowed its Roche lobe. How does the detection of this binary differ from the detection of an isolated neutron star?

Accepted Answer

A)  The outer layers of the larger star envelop the neutron star, so only the spectrum of the larger star is detected. 
B)  This binary may emit intense X-rays while an isolated neutron star emits radio waves. 
C)  The interaction of the larger star with the neutron star may slow the neutron star's rotation to the point where it no longer rotates. One then sees a steady radio beam rather than the series of pulses that the lighthouse model predicts for an isolated neutron star. 
D)  The spectrum of the larger star swamps the spectrum of the neutron star, thus showing a standard thermal blackbody spectrum. An isolated neutron star produces a nonthermal radiation spectrum. 
A)  The outer layers of the larger star envelop the neutron star, so only the spectrum of the larger star is detected. 
B)  This binary may emit intense X-rays while an isolated neutron star emits radio waves. 
C)  The interaction of the larger star with the neutron star may slow the neutron star's rotation to the point where it no longer rotates. One then sees a steady radio beam rather than the series of pulses that the lighthouse model predicts for an isolated neutron star. 
D)  The spectrum of the larger star swamps the spectrum of the neutron star, thus showing a standard thermal blackbody spectrum. An isolated neutron star produces a nonthermal radiation spectrum.

Question 6

A star ascending the red-giant branch for the second time in the asymptotic giant branch (AGB) phase will have

Accepted Answer

A)  no nuclear reactions in the core, but a helium-fusion shell outside the core, which itself is surrounded by a shell of hydrogen. 
B)  no fusion reactions; the star has used up all its nuclear fuel. 
C)  hydrogen-fusion reactions occurring in the core. 
D)  no nuclear reactions occurring in the core but hydrogen fusion in a shell outside the core. 
A)  no nuclear reactions in the core, but a helium-fusion shell outside the core, which itself is surrounded by a shell of hydrogen. 
B)  no fusion reactions; the star has used up all its nuclear fuel. 
C)  hydrogen-fusion reactions occurring in the core. 
D)  no nuclear reactions occurring in the core but hydrogen fusion in a shell outside the core.

Question 7

Consider a group of stars with masses up to 8 times the mass of the Sun. Stars of which masses will pass along the horizontal branch?

Accepted Answer

A)  less than 0.4 MSun 
B)  0.4 MSun to 2 MSun only 
C)  2 MSun to 8 MSun only 
D)  all stars 0.4 MSun to 8 MSun 
A)  less than 0.4 MSun 
B)  0.4 MSun to 2 MSun only 
C)  2 MSun to 8 MSun only 
D)  all stars 0.4 MSun to 8 MSun

Question 8

How is it that white dwarfs, which are relatively small, can have surface temperatures of several tens of thousands of kelvins?

Accepted Answer

A)  They are actually very similar in size and temperature to small main-sequence stars like red dwarfs. 
B)  The nuclear fusion in the core of a white dwarf involves carbon and oxygen, and this produces more energy and heat than either hydrogen or helium fusion. 
C)  The surface of the white dwarf is actually the core since the cooler outer layers have been blown off. 
D)  Because white dwarfs are fully convective, the nuclear fusion takes place on the surface. 
A)  They are actually very similar in size and temperature to small main-sequence stars like red dwarfs. 
B)  The nuclear fusion in the core of a white dwarf involves carbon and oxygen, and this produces more energy and heat than either hydrogen or helium fusion. 
C)  The surface of the white dwarf is actually the core since the cooler outer layers have been blown off. 
D)  Because white dwarfs are fully convective, the nuclear fusion takes place on the surface.

Question 9

The shell of a planetary nebula is measured by the Doppler shift of emission lines to be expanding outward at a speed of 104 m/s, while its radius is measured to be 1 ly, or about 1016 m. Roughly how long has the shell been expanding? (Hint: 1 year = 3.15 *107 sec.)

Accepted Answer

A)  30 years 
B)  30,000 years 
C)  30 million years 
D)  1012 years 
A)  30 years 
B)  30,000 years 
C)  30 million years 
D)  1012 years

Question 10

How many neutrinos from SN 1987A were detected on Earth?

Accepted Answer

A)  none 
B)  about 400,000 
C)  8 * 1017 
D)  20 
A)  none 
B)  about 400,000 
C)  8 * 1017 
D)  20

Question 11

The one characteristic shared by all solitary white dwarf stars is that they

Accepted Answer

A)  have stopped generating thermonuclear energy but continue to shrink, thereby releasing gravitational energy as heat. 
B)  have never generated either thermonuclear or gravitational energy but are slowly cooling after their production in a supernova explosion. 
C)  are generating thermonuclear energy but are maintaining a constant radius and hence are not releasing gravitational energy. 
D)  have ceased to generate energy by thermonuclear processes or gravitational contraction and are slowly cooling down. 
A)  have stopped generating thermonuclear energy but continue to shrink, thereby releasing gravitational energy as heat. 
B)  have never generated either thermonuclear or gravitational energy but are slowly cooling after their production in a supernova explosion. 
C)  are generating thermonuclear energy but are maintaining a constant radius and hence are not releasing gravitational energy. 
D)  have ceased to generate energy by thermonuclear processes or gravitational contraction and are slowly cooling down.

Question 12

What prevents a neutron star from collapsing and becoming a black hole?

Accepted Answer

A)  Gravity in the neutron star is balanced by an outward force due to neutron degeneracy. 
B)  Gravity is balanced in neutron stars by the outward centrifugal force produced by their rapid rotation. 
C)  Gravity in the neutron star is balanced by an outward force due to gas pressure, as in the Sun. 
D)  Neutron stars are solid, and, like any solid sphere, they are held up by the repulsive forces between atoms in the solid matter. 
A)  Gravity in the neutron star is balanced by an outward force due to neutron degeneracy. 
B)  Gravity is balanced in neutron stars by the outward centrifugal force produced by their rapid rotation. 
C)  Gravity in the neutron star is balanced by an outward force due to gas pressure, as in the Sun. 
D)  Neutron stars are solid, and, like any solid sphere, they are held up by the repulsive forces between atoms in the solid matter.

Question 13

Which of these statements about white dwarfs is FALSE?

Accepted Answer

A)  They generate energy by core fusion of carbon and hydrogen to produce oxygen. 
B)  Novae are generated by white dwarfs in close binary systems. 
C)  A white dwarf can be the source of more than one nova. 
D)  The Chandrasekhar limit restricts the maximum mass of a white dwarf. 
A)  They generate energy by core fusion of carbon and hydrogen to produce oxygen. 
B)  Novae are generated by white dwarfs in close binary systems. 
C)  A white dwarf can be the source of more than one nova. 
D)  The Chandrasekhar limit restricts the maximum mass of a white dwarf.

Question 14

A white dwarf star, as it evolves, undergoes which of these changes?

Accepted Answer

A)  Its temperature remains constant, but its radius and therefore its luminosity decrease. 
B)  Luminosity and size decrease while its temperature remains constant. 
C)  It shrinks in size, the resulting release of gravitational energy keeping both luminosity and temperature constant. 
D)  Luminosity and temperature decrease. 
A)  Its temperature remains constant, but its radius and therefore its luminosity decrease. 
B)  Luminosity and size decrease while its temperature remains constant. 
C)  It shrinks in size, the resulting release of gravitational energy keeping both luminosity and temperature constant. 
D)  Luminosity and temperature decrease.

Question 15

A pulsar is a(n)

Accepted Answer

A)  rapidly spinning neutron star. 
B)  type of variable star, pulsating rapidly in size and brightness. 
C)  very precise interstellar beacon perhaps operated by intelligent life-forms. 
D)  accretion disk around a black hole, emitting light as matter is accumulated on the disk. 
A)  rapidly spinning neutron star. 
B)  type of variable star, pulsating rapidly in size and brightness. 
C)  very precise interstellar beacon perhaps operated by intelligent life-forms. 
D)  accretion disk around a black hole, emitting light as matter is accumulated on the disk.

Question 16

A planetary nebula is a

Accepted Answer

A)  cloud of gas surrounding a very young star in which planets are expected to form. 
B)  spherical, rapidly expanding cloud of gas produced by a supernova explosion. 
C)  gas cloud surrounding a planet after its formation. 
D)  shell of gases ejected from the surface of red giant star. 
A)  cloud of gas surrounding a very young star in which planets are expected to form. 
B)  spherical, rapidly expanding cloud of gas produced by a supernova explosion. 
C)  gas cloud surrounding a planet after its formation. 
D)  shell of gases ejected from the surface of red giant star.

Question 17

In units of the Sun's mass, the original mass of the star that exploded to form supernova 1987A was probably about

Accepted Answer

A)  1.4. 
B)  40. 
C)  less than 1. 
D)  20. 
A)  1.4. 
B)  40. 
C)  less than 1. 
D)  20.

Question 18

Which of these properties does NOT characterize a massive supergiant star?

Accepted Answer

A)  high mass-loss rates caused by enormous stellar winds 
B)  longer and longer time periods required to complete each stage in nucleosynthesis because of the large amount of fuel to be consumed 
C)  circumstellar shells of ejected gas 
D)  fusion in concentric shells surrounding the core 
A)  high mass-loss rates caused by enormous stellar winds 
B)  longer and longer time periods required to complete each stage in nucleosynthesis because of the large amount of fuel to be consumed 
C)  circumstellar shells of ejected gas 
D)  fusion in concentric shells surrounding the core

Question 19

A neutron star is detected from Earth as a pulsar by its regular radio pulses only if Earth lies

Accepted Answer

A)  in the neutron star's "equator," the plane perpendicular to its spin axis. 
B)  within the path of the narrow beam of radiation being generated by the neutron star along its magnetic axis as the star rotates rapidly. 
C)  in the plane of the neutron star's magnetic equator, halfway between its magnetic poles. 
D)  directly above the rotation axis of the rotating neutron star. 
A)  in the neutron star's "equator," the plane perpendicular to its spin axis. 
B)  within the path of the narrow beam of radiation being generated by the neutron star along its magnetic axis as the star rotates rapidly. 
C)  in the plane of the neutron star's magnetic equator, halfway between its magnetic poles. 
D)  directly above the rotation axis of the rotating neutron star.

Question 20

White dwarf stars are supported from gravitational collapse by

Accepted Answer

A)  centrifugal force due to rapid rotation. 
B)  degenerate-electron pressure. 
C)  nuclear fusion reactions in their cores. 
D)  nuclear fusion reactions in a shell around the core. 
A)  centrifugal force due to rapid rotation. 
B)  degenerate-electron pressure. 
C)  nuclear fusion reactions in their cores. 
D)  nuclear fusion reactions in a shell around the core.

How do magnetars form?

What is the origin of millisecond pulsars?

Do neutron stars have atmospheres?

In astronomical terms, planetary nebulae are

A binary system is formed with a neutron star and another star that has overflowed its Roche lobe. How does the detection of this binary differ from the detection of an isolated neutron star?

A star ascending the red-giant branch for the second time in the asymptotic giant branch (AGB) phase will have

Consider a group of stars with masses up to 8 times the mass of the Sun. Stars of which masses will pass along the horizontal branch?

How is it that white dwarfs, which are relatively small, can have surface temperatures of several tens of thousands of kelvins?

The shell of a planetary nebula is measured by the Doppler shift of emission lines to be expanding outward at a speed of 10⁴ m/s, while its radius is measured to be 1 ly, or about 10¹⁶ m. Roughly how long has the shell been expanding? (Hint: 1 year = 3.15 *10⁷ sec.)

How many neutrinos from SN 1987A were detected on Earth?

The one characteristic shared by all solitary white dwarf stars is that they

What prevents a neutron star from collapsing and becoming a black hole?

Which of these statements about white dwarfs is FALSE?

A white dwarf star, as it evolves, undergoes which of these changes?

A pulsar is a(n)

A planetary nebula is a

In units of the Sun's mass, the original mass of the star that exploded to form supernova 1987A was probably about

Which of these properties does NOT characterize a massive supergiant star?

A neutron star is detected from Earth as a pulsar by its regular radio pulses only if Earth lies

White dwarf stars are supported from gravitational collapse by

Discovering the Night Sky

Gravitation and the Motion of the Planets

Light and Telescopes

Atomic Physics and Spectra

Exoplanets and the Formation of Planetary Systems

Formation of the Solar System

Earth and the Moon

The Other Terrestrial Planets

The Outer Planets

Vagabonds of the Solar System

The Sun: Our Extraordinary Star

Characterizing Stars

The Lives of Stars From Birth Through Middle Age

Black Holes: Matters of Gravity

The Milky Way Galaxy

Galaxies

Quasars and Other Active Galaxies

Cosmology

Astrobiology

Filters

Exam 14: The Death of Stars

How do magnetars form?

What is the origin of millisecond pulsars?

Do neutron stars have atmospheres?

In astronomical terms, planetary nebulae are

A binary system is formed with a neutron star and another star that has overflowed its Roche lobe. How does the detection of this binary differ from the detection of an isolated neutron star?

A star ascending the red-giant branch for the second time in the asymptotic giant branch (AGB) phase will have

Consider a group of stars with masses up to 8 times the mass of the Sun. Stars of which masses will pass along the horizontal branch?

How is it that white dwarfs, which are relatively small, can have surface temperatures of several tens of thousands of kelvins?

The shell of a planetary nebula is measured by the Doppler shift of emission lines to be expanding outward at a speed of 104 m/s, while its radius is measured to be 1 ly, or about 1016 m. Roughly how long has the shell been expanding? (Hint: 1 year = 3.15 *107 sec.)

How many neutrinos from SN 1987A were detected on Earth?

The one characteristic shared by all solitary white dwarf stars is that they

What prevents a neutron star from collapsing and becoming a black hole?

Which of these statements about white dwarfs is FALSE?

A white dwarf star, as it evolves, undergoes which of these changes?

A pulsar is a(n)

A planetary nebula is a

In units of the Sun's mass, the original mass of the star that exploded to form supernova 1987A was probably about

Which of these properties does NOT characterize a massive supergiant star?

A neutron star is detected from Earth as a pulsar by its regular radio pulses only if Earth lies

White dwarf stars are supported from gravitational collapse by

Discovering the Night Sky

Gravitation and the Motion of the Planets

Light and Telescopes

Atomic Physics and Spectra

Exoplanets and the Formation of Planetary Systems

Formation of the Solar System

Earth and the Moon

The Other Terrestrial Planets

The Outer Planets

Vagabonds of the Solar System

The Sun: Our Extraordinary Star

Characterizing Stars

The Lives of Stars From Birth Through Middle Age

Black Holes: Matters of Gravity

The Milky Way Galaxy

Galaxies

Quasars and Other Active Galaxies

Cosmology

Astrobiology

Filters

The shell of a planetary nebula is measured by the Doppler shift of emission lines to be expanding outward at a speed of 10⁴ m/s, while its radius is measured to be 1 ly, or about 10¹⁶ m. Roughly how long has the shell been expanding? (Hint: 1 year = 3.15 *10⁷ sec.)