Question 1

During helium burning in a star's later life,the chemical element produced by the combination of helium nuclei is:

Accepted Answer

A)  the light isotope of helium, ³He. 
B)  heavy hydrogen, ²H. 
C)  beryllium, ⁸Be. 
D)  carbon, ¹²C. 
A)  the light isotope of helium, ³He. 
B)  heavy hydrogen, ²H. 
C)  beryllium, ⁸Be. 
D)  carbon, ¹²C.

Question 2

Thermonuclear reactions convert hydrogen into helium in the core of a star during which phase of a star's life?

Accepted Answer

A)  main-sequence phase 
B)  protostar phase 
C)  horizontal-branch phase 
D)  as the star moves up the red giant branch for the first time 
A)  main-sequence phase 
B)  protostar phase 
C)  horizontal-branch phase 
D)  as the star moves up the red giant branch for the first time

Question 3

Main-sequence stars can be divided into those with more than 75% of the mass of the Sun and those with less than this amount of mass.What is different about these two groups?

Accepted Answer

A)  The less massive group does not have enough mass to undergo nuclear fusion. 
B)  Stars in the less massive group are all fully convective. 
C)  Stars in the less massive group are all free floating bodies that have never been part of a binary system. 
D)  Some of the stars in the more massive group have evolved off the main sequence, while none of the stars in the less massive group have done so. 
A)  The less massive group does not have enough mass to undergo nuclear fusion. 
B)  Stars in the less massive group are all fully convective. 
C)  Stars in the less massive group are all free floating bodies that have never been part of a binary system. 
D)  Some of the stars in the more massive group have evolved off the main sequence, while none of the stars in the less massive group have done so.

Question 4

The helium flash is another name for a sudden:

Accepted Answer

A)  release of energy at the end of helium burning due to core contraction. 
B)  onset of helium fusion reactions in red giant and supergiant stars of any mass. 
C)  onset of helium fusion reactions in the core of a low-mass red giant star. 
D)  appearance of helium during a supernova explosion (explosion of a star at the end of its life). 
A)  release of energy at the end of helium burning due to core contraction. 
B)  onset of helium fusion reactions in red giant and supergiant stars of any mass. 
C)  onset of helium fusion reactions in the core of a low-mass red giant star. 
D)  appearance of helium during a supernova explosion (explosion of a star at the end of its life).

Question 5

Why do H II regions glow?

Accepted Answer

A)  The hydrogen cannot emit radiation because it is fully ionized, so the radiation comes from neighboring molecules of carbon monoxide. 
B)  The H II region collides with a giant molecular cloud exciting the molecules in the cloud to radiate. 
C)  Some H II ions unite with electrons to re-form neutral hydrogen. In this process, the electron passes from level to level in the atom and emits a cascade of photons. 
D)  Protons, which make up H II, collide with each other, resulting in gamma-ray emission from the nuclei. 
A)  The hydrogen cannot emit radiation because it is fully ionized, so the radiation comes from neighboring molecules of carbon monoxide. 
B)  The H II region collides with a giant molecular cloud exciting the molecules in the cloud to radiate. 
C)  Some H II ions unite with electrons to re-form neutral hydrogen. In this process, the electron passes from level to level in the atom and emits a cascade of photons. 
D)  Protons, which make up H II, collide with each other, resulting in gamma-ray emission from the nuclei.

Question 6

There are several mechanisms that can trigger star formation in a cold,dark nebula.In each mechanism,the key to star formation is:

Accepted Answer

A)  bathing the cold, dark nebula in ultraviolet radiation and sweeping away some of the colder material. 
B)  compressing the gas and dust so that gravitation will overcome the gas pressure. 
C)  heating the gas so that gas pressure will overcome gravitation. 
D)  subjecting the dark nebula to an intense magnetic field so that supersonic jets will form. 
A)  bathing the cold, dark nebula in ultraviolet radiation and sweeping away some of the colder material. 
B)  compressing the gas and dust so that gravitation will overcome the gas pressure. 
C)  heating the gas so that gas pressure will overcome gravitation. 
D)  subjecting the dark nebula to an intense magnetic field so that supersonic jets will form.

Question 7

What are the typical dimensions of a giant molecular cloud in interstellar space?

Accepted Answer

A)  the mass of about 1000 solar masses in a volume with a diameter of about 1000 ly 
B)  the mass of about 1 million solar masses in a volume with a diameter of about 100 ly 
C)  the mass of about 1 million solar masses in a volume with a diameter of about 100 AU, about the size of the solar system 
D)  the mass of about 1000 solar masses in a volume with a diameter of about 100 ly 
A)  the mass of about 1000 solar masses in a volume with a diameter of about 1000 ly 
B)  the mass of about 1 million solar masses in a volume with a diameter of about 100 ly 
C)  the mass of about 1 million solar masses in a volume with a diameter of about 100 AU, about the size of the solar system 
D)  the mass of about 1000 solar masses in a volume with a diameter of about 100 ly

Question 8

RR Lyrae stars are:

Accepted Answer

A)  pulsating stars that vary regularly, all with periods of less than one day. 
B)  rotating neutron stars with very rapid and regular brightness fluctuations. 
C)  eclipsing binary stars. 
D)  pulsating stars that vary irregularly, with periods of several hundred days. 
A)  pulsating stars that vary regularly, all with periods of less than one day. 
B)  rotating neutron stars with very rapid and regular brightness fluctuations. 
C)  eclipsing binary stars. 
D)  pulsating stars that vary irregularly, with periods of several hundred days.

Question 9

A low-mass red dwarf (0.08 M < M < 0.4 M)experiences which fusion reaction as the last fusion reaction in its core?

Accepted Answer

A)  hydrogen fusion 
B)  helium fusion 
C)  carbon fusion 
D)  silicon fusion 
A)  hydrogen fusion 
B)  helium fusion 
C)  carbon fusion 
D)  silicon fusion

Question 10

If one were to look for a star at the end of its protostar stage,one might observe in which wavelength region?

Accepted Answer

A)  ultraviolet 
B)  visible 
C)  infrared 
D)  radio 
A)  ultraviolet 
B)  visible 
C)  infrared 
D)  radio

Question 11

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 12

What is believed to prevent stars from being larger than a few hundred solar masses?

Accepted Answer

A)  Stars of larger mass would collapse under their own gravity and become black holes. 
B)  No interstellar clouds have masses of more than 100 solar masses. 
C)  The cores of larger-mass stars would run through their lives and explode before the stars finish contracting as protostars. 
D)  The temperature becomes so high that the excess mass is pushed back into space by radiation from the star. 
A)  Stars of larger mass would collapse under their own gravity and become black holes. 
B)  No interstellar clouds have masses of more than 100 solar masses. 
C)  The cores of larger-mass stars would run through their lives and explode before the stars finish contracting as protostars. 
D)  The temperature becomes so high that the excess mass is pushed back into space by radiation from the star.

Question 13

The Pauli exclusion principle:

Accepted Answer

A)  prevents high-mass stars from forming in low-mass interstellar clouds. 
B)  sets a limit to the crowding together of electrons in any given small volume of space. 
C)  limits the number of atoms that can become ionized in a star. 
D)  prevents two stars of the same spectral class from occupying the same binary star system. 
A)  prevents high-mass stars from forming in low-mass interstellar clouds. 
B)  sets a limit to the crowding together of electrons in any given small volume of space. 
C)  limits the number of atoms that can become ionized in a star. 
D)  prevents two stars of the same spectral class from occupying the same binary star system.

Question 14

The Jeans instability describes the:

Accepted Answer

A)  explosion of a star at the end of its life, the supernova phenomenon. 
B)  overcoming of gas pressure by self-gravity in a cold and dense interstellar cloud to form a star. 
C)  conditions under which sufficient numbers of neutrinos can trigger the collapse of an interstellar cloud. 
D)  expansion of a gas cloud after gravitational contraction because of build-up of great heat within the cloud from gravitational potential energy. 
A)  explosion of a star at the end of its life, the supernova phenomenon. 
B)  overcoming of gas pressure by self-gravity in a cold and dense interstellar cloud to form a star. 
C)  conditions under which sufficient numbers of neutrinos can trigger the collapse of an interstellar cloud. 
D)  expansion of a gas cloud after gravitational contraction because of build-up of great heat within the cloud from gravitational potential energy.

Question 15

How is an H II region formed?

Accepted Answer

A)  In a supernova explosion, large amounts of hydrogen are ionized, and this forms the H II region. 
B)  They are remnants of the earliest period in the universe when only hygrogen existed. They were ionized when the cosmic microwave background radiation was released. 
C)  They are hydrogen clouds ionized by the radiation from hot O and B type stars. 
D)  They are hydrogen clouds ionized in the eruption of the T-Tauri phase of the star that they surround. 
A)  In a supernova explosion, large amounts of hydrogen are ionized, and this forms the H II region. 
B)  They are remnants of the earliest period in the universe when only hygrogen existed. They were ionized when the cosmic microwave background radiation was released. 
C)  They are hydrogen clouds ionized by the radiation from hot O and B type stars. 
D)  They are hydrogen clouds ionized in the eruption of the T-Tauri phase of the star that they surround.

Question 16

A relatively fast star escapes an open cluster.What does this do to the stability of the remaining cluster?

Accepted Answer

A)  The remaining cluster becomes more stable because only the slower stars are left. 
B)  The gravitational attraction of the escaping star tends to pull other stars after it, thus leading to the dissipation of the entire cluster. 
C)  The remaining cluster becomes less stable because the mass and thus the escape speed are reduced. 
D)  Because of the conservation of momentum, a second star must be expelled from the cluster in the opposite direction. The remaining cluster is then as stable as it was originally. 
A)  The remaining cluster becomes more stable because only the slower stars are left. 
B)  The gravitational attraction of the escaping star tends to pull other stars after it, thus leading to the dissipation of the entire cluster. 
C)  The remaining cluster becomes less stable because the mass and thus the escape speed are reduced. 
D)  Because of the conservation of momentum, a second star must be expelled from the cluster in the opposite direction. The remaining cluster is then as stable as it was originally.

Question 17

How do massive stars normally end their lives?

Accepted Answer

A)  Massive stars gradually shrink to the size of Earth. 
B)  We don't know how massive stars normally end their lives since their lifetimes are longer than the age of the universe. 
C)  Massive stars collapse and become black holes. 
D)  Massive stars explode. 
A)  Massive stars gradually shrink to the size of Earth. 
B)  We don't know how massive stars normally end their lives since their lifetimes are longer than the age of the universe. 
C)  Massive stars collapse and become black holes. 
D)  Massive stars explode.

Question 18

When is electron degeneracy pressure important in a star?

Accepted Answer

A)  just before the start of helium burning in the core 
B)  during core hydrogen burning 
C)  in a Cepheid variable that is burning helium in its core 
D)  in a protostar evolving toward the main sequence 
A)  just before the start of helium burning in the core 
B)  during core hydrogen burning 
C)  in a Cepheid variable that is burning helium in its core 
D)  in a protostar evolving toward the main sequence

Question 19

Our solar system could have formed from a _____ dense core.

Accepted Answer

A)  low-mass, non-rotating 
B)  low-mass, rotating 
C)  high-mass, non-rotating 
D)  high-mass, rotating 
A)  low-mass, non-rotating 
B)  low-mass, rotating 
C)  high-mass, non-rotating 
D)  high-mass, rotating

Question 20

Which object (if any)is a star in the sense that its main source of energy is nuclear fusion?

Accepted Answer

A)  a T Tauri star 
B)  a sub-brown dwarf 
C)  a brown dwarf 
D)  None of these has nuclear fusion as its main energy source. 
A)  a T Tauri star 
B)  a sub-brown dwarf 
C)  a brown dwarf 
D)  None of these has nuclear fusion as its main energy source.

During helium burning in a star's later life,the chemical element produced by the combination of helium nuclei is:

Thermonuclear reactions convert hydrogen into helium in the core of a star during which phase of a star's life?

Main-sequence stars can be divided into those with more than 75% of the mass of the Sun and those with less than this amount of mass.What is different about these two groups?

The helium flash is another name for a sudden:

Why do H II regions glow?

There are several mechanisms that can trigger star formation in a cold,dark nebula.In each mechanism,the key to star formation is:

What are the typical dimensions of a giant molecular cloud in interstellar space?

RR Lyrae stars are:

A low-mass red dwarf (0.08 M < M < 0.4 M)experiences which fusion reaction as the last fusion reaction in its core?

If one were to look for a star at the end of its protostar stage,one might observe in which wavelength region?

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:

What is believed to prevent stars from being larger than a few hundred solar masses?

The Pauli exclusion principle:

The Jeans instability describes the:

How is an H II region formed?

A relatively fast star escapes an open cluster.What does this do to the stability of the remaining cluster?

How do massive stars normally end their lives?

When is electron degeneracy pressure important in a star?

Our solar system could have formed from a _____ dense core.

Which object (if any)is a star in the sense that its main source of energy is nuclear fusion?

Discovering the Night Sky

Gravitation and the Waltz of the Planets

Light and Telescopes

Formation of the Solar System and Other Planetary Systems

Exoplanets

The Terrestrial Planets and Their Moons

The Outer Planets and Their Moons

Vagabonds of the Solar System

The Sun: Our Extraordinary Ordinary Star

Characterizing Stars

The Deaths and Remnants of Stars

The Galaxies

Cosmology

Astrobiology

Filters

Exam 11: The Lives of the Stars From Birth Through Middle Age

During helium burning in a star's later life,the chemical element produced by the combination of helium nuclei is:

Thermonuclear reactions convert hydrogen into helium in the core of a star during which phase of a star's life?

Main-sequence stars can be divided into those with more than 75% of the mass of the Sun and those with less than this amount of mass.What is different about these two groups?

The helium flash is another name for a sudden:

Why do H II regions glow?

There are several mechanisms that can trigger star formation in a cold,dark nebula.In each mechanism,the key to star formation is:

What are the typical dimensions of a giant molecular cloud in interstellar space?

RR Lyrae stars are:

A low-mass red dwarf (0.08 M < M < 0.4 M)experiences which fusion reaction as the last fusion reaction in its core?

If one were to look for a star at the end of its protostar stage,one might observe in which wavelength region?

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:

What is believed to prevent stars from being larger than a few hundred solar masses?

The Pauli exclusion principle:

The Jeans instability describes the:

How is an H II region formed?

A relatively fast star escapes an open cluster.What does this do to the stability of the remaining cluster?

How do massive stars normally end their lives?

When is electron degeneracy pressure important in a star?

Our solar system could have formed from a _____ dense core.

Which object (if any)is a star in the sense that its main source of energy is nuclear fusion?

Discovering the Night Sky

Gravitation and the Waltz of the Planets

Light and Telescopes

Formation of the Solar System and Other Planetary Systems

Exoplanets

The Terrestrial Planets and Their Moons

The Outer Planets and Their Moons

Vagabonds of the Solar System

The Sun: Our Extraordinary Ordinary Star

Characterizing Stars

The Deaths and Remnants of Stars

The Galaxies

Cosmology

Astrobiology

Filters