Question 1

Which of these statements about the rate of stellar evolution is true?

Accepted Answer

A)  The more massive the original star, the faster is the evolution. 
B)  The chemical makeup of the original nebula is the major factor in deciding the rate of evolution, whatever the mass of the star. 
C)  Star mass has no bearing on stellar evolution since all stars evolve at the same rate, controlled by nuclear fusion. 
D)  The more massive the original star, the slower is the evolution since there is more material for thermonuclear burning. 
A)  The more massive the original star, the faster is the evolution. 
B)  The chemical makeup of the original nebula is the major factor in deciding the rate of evolution, whatever the mass of the star. 
C)  Star mass has no bearing on stellar evolution since all stars evolve at the same rate, controlled by nuclear fusion. 
D)  The more massive the original star, the slower is the evolution since there is more material for thermonuclear burning.

Question 2

The end of the life of a red dwarf star is predicted to be a sphere of almost pure helium. But no such spheres have been detected. What do astronomers believe is the reason?

Accepted Answer

A)  These helium stars are very dim and consequently hard to detect. 
B)  There are very few red dwarfs, so their end products are expected to be rare. 
C)  The evolution rate for red dwarfs is so slow that none has yet evolved to its end stage. 
D)  Helium is a relatively light material, so these helium spheres are expected to dissipate in a short time. 
A)  These helium stars are very dim and consequently hard to detect. 
B)  There are very few red dwarfs, so their end products are expected to be rare. 
C)  The evolution rate for red dwarfs is so slow that none has yet evolved to its end stage. 
D)  Helium is a relatively light material, so these helium spheres are expected to dissipate in a short time.

Question 3

Which of these important atomic or molecular species is particularly difficult to detect in the interstellar medium?

Accepted Answer

A)  molecular hydrogen (H2) 
B)  atomic hydrogen (H) 
C)  carbon monoxide (CO) 
D)  water vapor (H2O) 
A)  molecular hydrogen (H2) 
B)  atomic hydrogen (H) 
C)  carbon monoxide (CO) 
D)  water vapor (H2O)

Question 4

What characteristic of Cepheid variables makes them extremely useful to astronomers?

Accepted Answer

A)  The absolute magnitude of Cepheid variables is related directly to their period of pulsation. 
B)  The absolute magnitude of Cepheid variables is directly related to their diameter. 
C)  The absolute magnitude of Cepheid variables is related directly to their metal content (heavy element abundance). 
D)  The absolute magnitude of Cepheid variables is related directly to their surface temperature. 
A)  The absolute magnitude of Cepheid variables is related directly to their period of pulsation. 
B)  The absolute magnitude of Cepheid variables is directly related to their diameter. 
C)  The absolute magnitude of Cepheid variables is related directly to their metal content (heavy element abundance). 
D)  The absolute magnitude of Cepheid variables is related directly to their surface temperature.

Question 5

Where are emission nebulae (also known as H II regions) found?

Accepted Answer

A)  in or near old open clusters 
B)  around hot stars 
C)  in globular star clusters 
D)  around low-mass stars 
A)  in or near old open clusters 
B)  around hot stars 
C)  in globular star clusters 
D)  around low-mass stars

Question 6

What does the term "hydrostatic equilibrium" mean in reference to stars?

Accepted Answer

A)  The pressure throughout a star is constant. 
B)  The pressure within a star is sufficient to cause the star to expand at a constant rate. 
C)  The gravitational force within a star is sufficient to cause the star to collapse inward at a steady rate. 
D)  Each layer within a star is in balance with respect to pressure and gravity. 
A)  The pressure throughout a star is constant. 
B)  The pressure within a star is sufficient to cause the star to expand at a constant rate. 
C)  The gravitational force within a star is sufficient to cause the star to collapse inward at a steady rate. 
D)  Each layer within a star is in balance with respect to pressure and gravity.

Question 7

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 hydrogen 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 hydrogen 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 8

What is the MOST important use of Cepheid variables for astronomers?

Accepted Answer

A)  The distance to a Cepheid variable can be found very easily. 
B)  The characteristics of the pulsation of a Cepheid variable can be used to investigate conditions in the core of the star. 
C)  The diameter of a Cepheid variable can be found very easily. 
D)  The metal content of a Cepheid variable can be found very easily. 
A)  The distance to a Cepheid variable can be found very easily. 
B)  The characteristics of the pulsation of a Cepheid variable can be used to investigate conditions in the core of the star. 
C)  The diameter of a Cepheid variable can be found very easily. 
D)  The metal content of a Cepheid variable can be found very easily.

Question 9

A brown dwarf is a(n)

Accepted Answer

A)  object intermediate between a planet and a star, with not enough mass to begin normal nuclear reactions in its core. 
B)  general name for an object similar to the planet Jupiter. 
C)  star whose blackbody spectrum peaks in the brown region of the visible spectrum. 
D)  star of less than about 1.5 solar masses at the very end of its life, after it has cooled to near invisibility. 
A)  object intermediate between a planet and a star, with not enough mass to begin normal nuclear reactions in its core. 
B)  general name for an object similar to the planet Jupiter. 
C)  star whose blackbody spectrum peaks in the brown region of the visible spectrum. 
D)  star of less than about 1.5 solar masses at the very end of its life, after it has cooled to near invisibility.

Question 10

Which of these facts referring to stars in a cluster is NOT particularly useful for interpreting the evolution of these stars?

Accepted Answer

A)  The stars are all at the same distance from Earth, so one can easily relate their apparent magnitudes to their true luminosities. 
B)  The stars all formed at about the same time. 
C)  The stars formed from the same mix of chemical elements but with a mix of original masses. 
D)  The majority of the material in these stars is hydrogen. 
A)  The stars are all at the same distance from Earth, so one can easily relate their apparent magnitudes to their true luminosities. 
B)  The stars all formed at about the same time. 
C)  The stars formed from the same mix of chemical elements but with a mix of original masses. 
D)  The majority of the material in these stars is hydrogen.

Question 11

What is the difference between an extrasolar planet and a sub-brown dwarf?

Accepted Answer

A)  There is no difference. These are two different names for the same object. 
B)  In its core a sub-brown dwarf generates a limited amount of energy through fusion of deuterium into helium. An extrasolar planet generates no fusion energy. 
C)  In its core a sub-brown dwarf generates a limited amount of energy through fusion of lithium into helium. An extrasolar planet generates no fusion energy. 
D)  An extrasolar planet orbits a star; a sub-brown dwarf does not. Otherwise, they are the same. 
A)  There is no difference. These are two different names for the same object. 
B)  In its core a sub-brown dwarf generates a limited amount of energy through fusion of deuterium into helium. An extrasolar planet generates no fusion energy. 
C)  In its core a sub-brown dwarf generates a limited amount of energy through fusion of lithium into helium. An extrasolar planet generates no fusion energy. 
D)  An extrasolar planet orbits a star; a sub-brown dwarf does not. Otherwise, they are the same.

Question 12

Red dwarfs are fully convective. In this, they are like

Accepted Answer

A)  white dwarfs. 
B)  brown dwarfs. 
C)  the Sun. 
D)  variable stars. 
A)  white dwarfs. 
B)  brown dwarfs. 
C)  the Sun. 
D)  variable stars.

Question 13

What is the "safety valve" that prevents normal (nondegenerate) stars from self-destructing?

Accepted Answer

A)  If the pressure rises, the volume occupied by the matter decreases, reducing the nuclear reaction rate. 
B)  If a part of a star where thermonuclear reactions are occurring is suddenly heated, it expands and cools. 
C)  If thermonuclear reactions proceed too quickly, the star runs out of fuel before anything drastic happens. 
D)  If the temperature rises, the thermonuclear reaction rate increases to match it. 
A)  If the pressure rises, the volume occupied by the matter decreases, reducing the nuclear reaction rate. 
B)  If a part of a star where thermonuclear reactions are occurring is suddenly heated, it expands and cools. 
C)  If thermonuclear reactions proceed too quickly, the star runs out of fuel before anything drastic happens. 
D)  If the temperature rises, the thermonuclear reaction rate increases to match it.

Question 14

In which one of these locations are clumps of gas MOST likely to be collapsing to form stars?

Accepted Answer

A)  outer part of the solar system 
B)  globular cluster 
C)  reflection nebulae 
D)  giant molecular clouds 
A)  outer part of the solar system 
B)  globular cluster 
C)  reflection nebulae 
D)  giant molecular clouds

Question 15

Consider stars of these masses (in solar masses). Which one would be expected to experience a helium flash?

Accepted Answer

A)  0.2 
B)  1.2 
C)  2.6 
D)  4.2 
A)  0.2 
B)  1.2 
C)  2.6 
D)  4.2

Question 16

Over which of these stages of stellar evolution does the radius of a star remain approximately constant?

Accepted Answer

A)  main-sequence phase 
B)  red giant phase 
C)  birth and initial formation 
D)  The radius of a star is approximately constant in ALL of these phases. 
A)  main-sequence phase 
B)  red giant phase 
C)  birth and initial formation 
D)  The radius of a star is approximately constant in ALL of these phases.

Question 17

In terms of the mass and lifetime of a star, which of these statements is true?

Accepted Answer

A)  The mass of a star has no bearing on the length of a star's life or the speed of its evolution. 
B)  Stars of about 1 solar mass have the shortest lives; less massive stars evolve slowly and live a longer time, while more massive stars have long lives because of the large amount of fuel they contain. 
C)  The less massive the star, the shorter is its life because it has less hydrogen "fuel" to burn. 
D)  The more massive the star, the faster it evolves through its life. 
A)  The mass of a star has no bearing on the length of a star's life or the speed of its evolution. 
B)  Stars of about 1 solar mass have the shortest lives; less massive stars evolve slowly and live a longer time, while more massive stars have long lives because of the large amount of fuel they contain. 
C)  The less massive the star, the shorter is its life because it has less hydrogen "fuel" to burn. 
D)  The more massive the star, the faster it evolves through its life.

Question 18

The solar system could have formed from a

Accepted Answer

A)  nonrotating Bok globule with a relatively low density. 
B)  rotating Bok globule with a relatively low density. 
C)  nonrotating Bok globule with a relatively high density. 
D)  rotating Bok globule with a relatively high density. 
A)  nonrotating Bok globule with a relatively low density. 
B)  rotating Bok globule with a relatively low density. 
C)  nonrotating Bok globule with a relatively high density. 
D)  rotating Bok globule with a relatively high density.

Question 19

When a star like the Sun expands to become a red giant, its surface will move outward at about 10 km/s. For an observer looking directly at the Sun, what will be the Doppler-shifted wavelength of the H $\alpha$  line (in nm)? From a source at rest, the H $\alpha$  wavelength is 656.28 nm.

Accepted Answer

A)  646.28 
B)  656.26 
C)  656.30 
D)  666.28 
A)  646.28 
B)  656.26 
C)  656.30 
D)  666.28

Question 20

What is unique about a low-mass red dwarf star compared with stars at other stages of evolution, such as main-sequence stars?

Accepted Answer

A)  A low-mass red dwarf is the smallest in size of any star. 
B)  Nuclear fusion occurs not in the core of a red dwarf but in a region just beneath its surface. 
C)  A red dwarf has the lowest surface temperature of any star. 
D)  Convection occurs throughout the interior of a red dwarf such that the star does not develop separate core and outer layer regions. 
A)  A low-mass red dwarf is the smallest in size of any star. 
B)  Nuclear fusion occurs not in the core of a red dwarf but in a region just beneath its surface. 
C)  A red dwarf has the lowest surface temperature of any star. 
D)  Convection occurs throughout the interior of a red dwarf such that the star does not develop separate core and outer layer regions.

Which of these statements about the rate of stellar evolution is true?

The end of the life of a red dwarf star is predicted to be a sphere of almost pure helium. But no such spheres have been detected. What do astronomers believe is the reason?

Which of these important atomic or molecular species is particularly difficult to detect in the interstellar medium?

What characteristic of Cepheid variables makes them extremely useful to astronomers?

Where are emission nebulae (also known as H II regions) found?

What does the term "hydrostatic equilibrium" mean in reference to stars?

How is an H II region formed?

What is the MOST important use of Cepheid variables for astronomers?

A brown dwarf is a(n)

Which of these facts referring to stars in a cluster is NOT particularly useful for interpreting the evolution of these stars?

What is the difference between an extrasolar planet and a sub-brown dwarf?

Red dwarfs are fully convective. In this, they are like

What is the "safety valve" that prevents normal (nondegenerate) stars from self-destructing?

In which one of these locations are clumps of gas MOST likely to be collapsing to form stars?

Consider stars of these masses (in solar masses). Which one would be expected to experience a helium flash?

Over which of these stages of stellar evolution does the radius of a star remain approximately constant?

In terms of the mass and lifetime of a star, which of these statements is true?

The solar system could have formed from a

When a star like the Sun expands to become a red giant, its surface will move outward at about 10 km/s. For an observer looking directly at the Sun, what will be the Doppler-shifted wavelength of the H _$\alpha$ line (in nm)? From a source at rest, the H _$\alpha$ wavelength is 656.28 nm.

What is unique about a low-mass red dwarf star compared with stars at other stages of evolution, such as main-sequence stars?

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

Which of these statements about the rate of stellar evolution is true?

The end of the life of a red dwarf star is predicted to be a sphere of almost pure helium. But no such spheres have been detected. What do astronomers believe is the reason?

Which of these important atomic or molecular species is particularly difficult to detect in the interstellar medium?

What characteristic of Cepheid variables makes them extremely useful to astronomers?

Where are emission nebulae (also known as H II regions) found?

What does the term "hydrostatic equilibrium" mean in reference to stars?

How is an H II region formed?

What is the MOST important use of Cepheid variables for astronomers?

A brown dwarf is a(n)

Which of these facts referring to stars in a cluster is NOT particularly useful for interpreting the evolution of these stars?

What is the difference between an extrasolar planet and a sub-brown dwarf?

Red dwarfs are fully convective. In this, they are like

What is the "safety valve" that prevents normal (nondegenerate) stars from self-destructing?

In which one of these locations are clumps of gas MOST likely to be collapsing to form stars?

Consider stars of these masses (in solar masses). Which one would be expected to experience a helium flash?

Over which of these stages of stellar evolution does the radius of a star remain approximately constant?

In terms of the mass and lifetime of a star, which of these statements is true?

The solar system could have formed from a

When a star like the Sun expands to become a red giant, its surface will move outward at about 10 km/s. For an observer looking directly at the Sun, what will be the Doppler-shifted wavelength of the H α\alphaα line (in nm)? From a source at rest, the H α\alphaα wavelength is 656.28 nm.

What is unique about a low-mass red dwarf star compared with stars at other stages of evolution, such as main-sequence stars?

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

When a star like the Sun expands to become a red giant, its surface will move outward at about 10 km/s. For an observer looking directly at the Sun, what will be the Doppler-shifted wavelength of the H _$\alpha$ line (in nm)? From a source at rest, the H _$\alpha$ wavelength is 656.28 nm.