Question 1

All stars on the main sequence

Accepted Answer

A)  generate energy by hydrogen fusion in their centers. 
B)  have approximately the same age, to within a few million years. 
C)  are changing slowly in size, by gravitational contraction. 
D)  are at a late stage of evolution, after the red giant stage. 
A)  generate energy by hydrogen fusion in their centers. 
B)  have approximately the same age, to within a few million years. 
C)  are changing slowly in size, by gravitational contraction. 
D)  are at a late stage of evolution, after the red giant stage.

Question 2

The Pleiades cluster consists of a number of bright stars wrapped in a cloud of gas and dust that appears blue. This cluster is an example of

Accepted Answer

A)  a giant molecular cloud. 
B)  a dark nebula. 
C)  a reflection nebula. 
D)  a stellar "nursery." 
A)  a giant molecular cloud. 
B)  a dark nebula. 
C)  a reflection nebula. 
D)  a stellar "nursery."

Question 3

Horizontal-branch stars have a wide range of temperatures and luminosities between 50 and 100 times that of the Sun, so they are in what stage of their lives?

Accepted Answer

A)  gravitational contraction before the start of core hydrogen burning 
B)  hydrogen shell burning, with a degenerate helium core 
C)  core helium burning and shell hydrogen burning 
D)  core helium burning only 
A)  gravitational contraction before the start of core hydrogen burning 
B)  hydrogen shell burning, with a degenerate helium core 
C)  core helium burning and shell hydrogen burning 
D)  core helium burning only

Question 4

Some protostars, when they evolve onto the main sequence, are fully convective and use convection to transport material all the way from the core to the surface. Which stars show this characteristic?

Accepted Answer

A)  only the smallest, of less than about 0.4 solar mass 
B)  intermediate stars, of about 0.4 solar mass up to about 4 solar masses 
C)  the largest, of more than about 4 solar masses 
D)  all protostars 
A)  only the smallest, of less than about 0.4 solar mass 
B)  intermediate stars, of about 0.4 solar mass up to about 4 solar masses 
C)  the largest, of more than about 4 solar masses 
D)  all protostars

Question 5

After it leaves the main sequence, a star of more than 1 solar mass moves generally to the right on the H-R diagram because the star's

Accepted Answer

A)  surface temperature is increasing while its radius is decreasing. 
B)  surface temperature is decreasing while its radius is increasing. 
C)  core is expanding while its outer layers are contracting. 
D)  core is expanding, causing its outer layers to expand as well. 
A)  surface temperature is increasing while its radius is decreasing. 
B)  surface temperature is decreasing while its radius is increasing. 
C)  core is expanding while its outer layers are contracting. 
D)  core is expanding, causing its outer layers to expand as well.

Question 6

In the first stage after main-sequence hydrogen fusion, the envelope of the star is pushed outward to expand. The nuclear reactions that produce the outward pressure for this expansion are

Accepted Answer

A)  hydrogen fusion in the core. 
B)  hydrogen fusion in the shell. 
C)  helium fusion in the core. 
D)  helium fusion in the shell. 
A)  hydrogen fusion in the core. 
B)  hydrogen fusion in the shell. 
C)  helium fusion in the core. 
D)  helium fusion in the shell.

Question 7

The "evolutionary track" of a star represents

Accepted Answer

A)  its orbit around the center of the galaxy in which it resides. 
B)  changes in its luminosity and temperature, as the star ages, on a graph of these two parameters. 
C)  its path across Earth's sky as a consequence of its true motion in space. 
D)  changes in its size and mass, as the star ages, on a graph of these two parameters. 
A)  its orbit around the center of the galaxy in which it resides. 
B)  changes in its luminosity and temperature, as the star ages, on a graph of these two parameters. 
C)  its path across Earth's sky as a consequence of its true motion in space. 
D)  changes in its size and mass, as the star ages, on a graph of these two parameters.

Question 8

In a list of the 100 brightest stars in the sky, MOST of them are

Accepted Answer

A)  white dwarfs. 
B)  main-sequence stars. 
C)  giants and supergiants. 
D)  brown dwarfs. 
A)  white dwarfs. 
B)  main-sequence stars. 
C)  giants and supergiants. 
D)  brown dwarfs.

Question 9

Suppose that an astronomy news item announces the discovery of a brown dwarf. What is it that has been discovered?

Accepted Answer

A)  prestellar object undergoing gravitational collapse 
B)  Plutolike object in the Kuiper belt, beyond the edge of the planetary system 
C)  object too large to be a planet but too small to be a star 
D)  protostar still embedded in the cloud of gas and dust from which it formed 
A)  prestellar object undergoing gravitational collapse 
B)  Plutolike object in the Kuiper belt, beyond the edge of the planetary system 
C)  object too large to be a planet but too small to be a star 
D)  protostar still embedded in the cloud of gas and dust from which it formed

Question 10

Main-sequence stars apparently are not larger than a few hundred solar masses. The reason stars of larger mass do NOT exist is that

Accepted Answer

A)  their temperatures becomes so high that their outer envelopes are expelled by the pressure of radiation inside them. 
B)  the thermonuclear reactions in such stars proceed so rapidly that the stars explode. 
C)  such stars contract directly to become planetlike objects. 
D)  interstellar clouds of greater mass break up to become binary or multiple-star systems, not single stars. 
A)  their temperatures becomes so high that their outer envelopes are expelled by the pressure of radiation inside them. 
B)  the thermonuclear reactions in such stars proceed so rapidly that the stars explode. 
C)  such stars contract directly to become planetlike objects. 
D)  interstellar clouds of greater mass break up to become binary or multiple-star systems, not single stars.

Question 11

An open cluster has

Accepted Answer

A)  a few hundred members, often very young and still embedded in the gas and dust from which they were formed. 
B)  hundreds of thousands of members, all very old, surrounded by very little interstellar gas and dust. 
C)  a few dozen members, the remnant of a globular cluster of stars from which most of the members have escaped. 
D)  many thousands of members of different ages. 
A)  a few hundred members, often very young and still embedded in the gas and dust from which they were formed. 
B)  hundreds of thousands of members, all very old, surrounded by very little interstellar gas and dust. 
C)  a few dozen members, the remnant of a globular cluster of stars from which most of the members have escaped. 
D)  many thousands of members of different ages.

Question 12

What physical mechanism is responsible for the oscillations in brightness that a Cepheid variable star undergoes?

Accepted Answer

A)  the fusion rate in the star's core varies periodically, changing the energy generation rate 
B)  the amount of ionized helium in the star's outer layers vary, changing the opacity 
C)  the fusion rate in the shell burning hydrogen varies, changing the energy generation rate 
D)  the star's outer layers cycle between convection and radiative transport, changing the temperature 
A)  the fusion rate in the star's core varies periodically, changing the energy generation rate 
B)  the amount of ionized helium in the star's outer layers vary, changing the opacity 
C)  the fusion rate in the shell burning hydrogen varies, changing the energy generation rate 
D)  the star's outer layers cycle between convection and radiative transport, changing the temperature

Question 13

Which of these mechanisms is NOT a common way in which star formation is triggered or started?

Accepted Answer

A)  collisions between interstellar clouds 
B)  heating of an interstellar cloud by radiation from embedded young stars 
C)  compression of an interstellar cloud by the shock waves from a supernova explosion 
D)  compression of an interstellar cloud by the pressure of light from nearby stars 
A)  collisions between interstellar clouds 
B)  heating of an interstellar cloud by radiation from embedded young stars 
C)  compression of an interstellar cloud by the shock waves from a supernova explosion 
D)  compression of an interstellar cloud by the pressure of light from nearby stars

Question 14

Which of these properties is NOT a characteristic of T Tauri stars?

Accepted Answer

A)  variations in brightness 
B)  ejection of mass into space 
C)  nuclear reactions in the core 
D)  emission lines in the spectrum 
A)  variations in brightness 
B)  ejection of mass into space 
C)  nuclear reactions in the core 
D)  emission lines in the spectrum

Question 15

How does a dense core collapse to become a star?

Accepted Answer

A)  The innermost part collapses first; then the outer part is drawn in by the gravity of the inner part. 
B)  The collapse is turbulent and chaotic, with no overall pattern. 
C)  The outer, less dense part falls in first and its weight accelerates the collapse of the inner part. 
D)  All parts of the cloud accelerate inward more or less smoothly and evenly. 
A)  The innermost part collapses first; then the outer part is drawn in by the gravity of the inner part. 
B)  The collapse is turbulent and chaotic, with no overall pattern. 
C)  The outer, less dense part falls in first and its weight accelerates the collapse of the inner part. 
D)  All parts of the cloud accelerate inward more or less smoothly and evenly.

Question 16

After the helium flash in a low-mass star,

Accepted Answer

A)  all nuclear reactions cease. 
B)  helium burning ceases in the core, but hydrogen burning continues in the layers around the core. 
C)  helium burning begins in the core, and hydrogen burning ceases in the layers around the core. 
D)  helium burning begins in the core, and hydrogen burning continues in the layers around the core. 
A)  all nuclear reactions cease. 
B)  helium burning ceases in the core, but hydrogen burning continues in the layers around the core. 
C)  helium burning begins in the core, and hydrogen burning ceases in the layers around the core. 
D)  helium burning begins in the core, and hydrogen burning continues in the layers around the core.

Question 17

In the H-R diagram shown in Figure 13-31b in the text, the brightest stars in the Pleiades cluster are not on the main sequence but away from it toward the upper right. Explain.

Accepted Answer

A)  The brightest stars have not yet reached the main sequence and are in the T Tauri phase. 
B)  The brightest stars have already evolved through the red giant phase and have now returned to the blue giant phase on their way to the white dwarf phase. 
C)  The brightest stars have already become white dwarf stars, as shown by their position. 
D)  These blue supergiant stars have already begun to evolve toward the red supergiant phase. 
A)  The brightest stars have not yet reached the main sequence and are in the T Tauri phase. 
B)  The brightest stars have already evolved through the red giant phase and have now returned to the blue giant phase on their way to the white dwarf phase. 
C)  The brightest stars have already become white dwarf stars, as shown by their position. 
D)  These blue supergiant stars have already begun to evolve toward the red supergiant phase.

Question 18

What process is involved in the helium flash?

Accepted Answer

A)  An increase in temperature causes an increase in the nuclear reaction rate but has no effect on pressure. 
B)  An increase in the pressure causes a decrease in the temperature and the nuclear reaction rate. 
C)  An increase in temperature causes an increase in the pressure with no increase in the nuclear reaction rate. 
D)  An increase in the nuclear reaction rate causes an increase in the temperature and the pressure. 
A)  An increase in temperature causes an increase in the nuclear reaction rate but has no effect on pressure. 
B)  An increase in the pressure causes a decrease in the temperature and the nuclear reaction rate. 
C)  An increase in temperature causes an increase in the pressure with no increase in the nuclear reaction rate. 
D)  An increase in the nuclear reaction rate causes an increase in the temperature and the pressure.

Question 19

What wavelengths have astronomers used to map and study the distribution of the giant molecular clouds in space?

Accepted Answer

A)  X-ray 
B)  visible 
C)  ultraviolet 
D)  radio 
A)  X-ray 
B)  visible 
C)  ultraviolet 
D)  radio

Question 20

Consider stars of these masses (in solar masses). Which one would NOT be expected to experience a helium flash?

Accepted Answer

A)  0.2 
B)  0.8 
C)  1.2 
D)  1.8 
A)  0.2 
B)  0.8 
C)  1.2 
D)  1.8

All stars on the main sequence

The Pleiades cluster consists of a number of bright stars wrapped in a cloud of gas and dust that appears blue. This cluster is an example of

Horizontal-branch stars have a wide range of temperatures and luminosities between 50 and 100 times that of the Sun, so they are in what stage of their lives?

Some protostars, when they evolve onto the main sequence, are fully convective and use convection to transport material all the way from the core to the surface. Which stars show this characteristic?

After it leaves the main sequence, a star of more than 1 solar mass moves generally to the right on the H-R diagram because the star's

In the first stage after main-sequence hydrogen fusion, the envelope of the star is pushed outward to expand. The nuclear reactions that produce the outward pressure for this expansion are

The "evolutionary track" of a star represents

In a list of the 100 brightest stars in the sky, MOST of them are

Suppose that an astronomy news item announces the discovery of a brown dwarf. What is it that has been discovered?

Main-sequence stars apparently are not larger than a few hundred solar masses. The reason stars of larger mass do NOT exist is that

An open cluster has

What physical mechanism is responsible for the oscillations in brightness that a Cepheid variable star undergoes?

Which of these mechanisms is NOT a common way in which star formation is triggered or started?

Which of these properties is NOT a characteristic of T Tauri stars?

How does a dense core collapse to become a star?

After the helium flash in a low-mass star,

In the H-R diagram shown in Figure 13-31b in the text, the brightest stars in the Pleiades cluster are not on the main sequence but away from it toward the upper right. Explain.

What process is involved in the helium flash?

What wavelengths have astronomers used to map and study the distribution of the giant molecular clouds in space?

Consider stars of these masses (in solar masses). Which one would NOT be expected to experience a helium flash?

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 Death of Stars

Black Holes: Matters of Gravity

The Milky Way Galaxy

Galaxies

Quasars and Other Active Galaxies

Cosmology

Astrobiology

Filters

Exam 13: The Lives of Stars From Birth Through Middle Age

All stars on the main sequence

The Pleiades cluster consists of a number of bright stars wrapped in a cloud of gas and dust that appears blue. This cluster is an example of

Horizontal-branch stars have a wide range of temperatures and luminosities between 50 and 100 times that of the Sun, so they are in what stage of their lives?

Some protostars, when they evolve onto the main sequence, are fully convective and use convection to transport material all the way from the core to the surface. Which stars show this characteristic?

After it leaves the main sequence, a star of more than 1 solar mass moves generally to the right on the H-R diagram because the star's

In the first stage after main-sequence hydrogen fusion, the envelope of the star is pushed outward to expand. The nuclear reactions that produce the outward pressure for this expansion are

The "evolutionary track" of a star represents

In a list of the 100 brightest stars in the sky, MOST of them are

Suppose that an astronomy news item announces the discovery of a brown dwarf. What is it that has been discovered?

Main-sequence stars apparently are not larger than a few hundred solar masses. The reason stars of larger mass do NOT exist is that

An open cluster has

What physical mechanism is responsible for the oscillations in brightness that a Cepheid variable star undergoes?

Which of these mechanisms is NOT a common way in which star formation is triggered or started?

Which of these properties is NOT a characteristic of T Tauri stars?

How does a dense core collapse to become a star?

After the helium flash in a low-mass star,

In the H-R diagram shown in Figure 13-31b in the text, the brightest stars in the Pleiades cluster are not on the main sequence but away from it toward the upper right. Explain.

What process is involved in the helium flash?

What wavelengths have astronomers used to map and study the distribution of the giant molecular clouds in space?

Consider stars of these masses (in solar masses). Which one would NOT be expected to experience a helium flash?

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 Death of Stars

Black Holes: Matters of Gravity

The Milky Way Galaxy

Galaxies

Quasars and Other Active Galaxies

Cosmology

Astrobiology

Filters