Question 1

Cepheid stars are:

Accepted Answer

A)  giant stars that pulsate in brightness, size, and temperature. 
B)  white dwarf stars late in their evolutionary life. 
C)  members of binary systems in which one star periodically eclipses the other. 
D)  stars at an early stage in stellar evolution, pre-main-sequence. 
A)  giant stars that pulsate in brightness, size, and temperature. 
B)  white dwarf stars late in their evolutionary life. 
C)  members of binary systems in which one star periodically eclipses the other. 
D)  stars at an early stage in stellar evolution, pre-main-sequence.

Question 2

What are the stars in the lower part of the instability strip called?

Accepted Answer

A)  T Tauri stars 
B)  protostars 
C)  Cepheid variables 
D)  RR Lyrae variables 
A)  T Tauri stars 
B)  protostars 
C)  Cepheid variables 
D)  RR Lyrae variables

Question 3

The majority of the elements heavier than hydrogen and helium in the universe are believed to have originated in:

Accepted Answer

A)  the original Big Bang. 
B)  reflection nebulae. 
C)  giant molecular clouds. 
D)  the central cores of stars. 
A)  the original Big Bang. 
B)  reflection nebulae. 
C)  giant molecular clouds. 
D)  the central cores of stars.

Question 4

In Earth's solar system,a nebula is believed to have formed around the early Sun.Planetesimals gradually coalesced out of this nebula and accreted to form the planets-a process requiring a total of about 100 million years.How would you describe the Sun at the end of this process?

Accepted Answer

A)  The Sun was about halfway through its protostar phase. 
B)  The Sun had just become a pre-main-sequence star. 
C)  The Sun was at the end of its existence as a pre-main-sequence star. 
D)  The Sun had ended its pre-main-sequence phase and had become a main-sequence star. 
A)  The Sun was about halfway through its protostar phase. 
B)  The Sun had just become a pre-main-sequence star. 
C)  The Sun was at the end of its existence as a pre-main-sequence star. 
D)  The Sun had ended its pre-main-sequence phase and had become a main-sequence star.

Question 5

When any star on the main sequence was a protostar,it was:

Accepted Answer

A)  larger and hotter. 
B)  hotter but not necessarily larger. 
C)  cooler but not necessarily larger. 
D)  larger and cooler. 
A)  larger and hotter. 
B)  hotter but not necessarily larger. 
C)  cooler but not necessarily larger. 
D)  larger and cooler.

Question 6

It is now believed that MOST stars are:

Accepted Answer

A)  members of binary systems. 
B)  members of triple systems. 
C)  solitary stars. 
D)  variable stars. 
A)  members of binary systems. 
B)  members of triple systems. 
C)  solitary stars. 
D)  variable stars.

Question 7

Which important atomic or molecular species is 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 8

What causes the characteristic blue color of a reflection nebula?

Accepted Answer

A)  electrons dropping between energy levels n = 3 and n = 2 in hydrogen atoms 
B)  electrons dropping between energy levels n = 2 and n = 1 in hydrogen atoms 
C)  thermal blackbody radiation emitted by the hot gas 
D)  scattering of starlight from dust grains in the nebula 
A)  electrons dropping between energy levels n = 3 and n = 2 in hydrogen atoms 
B)  electrons dropping between energy levels n = 2 and n = 1 in hydrogen atoms 
C)  thermal blackbody radiation emitted by the hot gas 
D)  scattering of starlight from dust grains in the nebula

Question 9

Which component in the core of a star undergoing helium fusion leads to the behavior known as the "helium flash"?

Accepted Answer

A)  neutrinos since it is this component that, in interacting with helium nuclei, triggers the helium flash 
B)  helium since its density has to be above a certain limit to trigger this explosive event 
C)  electrons since they control the pressure, and pressure does not depend on temperature (Under these conditions, build-up of heat can occur without leading to the normal gas expansion and the resulting thermal equilibrium.) 
D)  remnant hydrogen since loss of this component allows uncontrolled helium burning rather than a uniform rate of energy production 
A)  neutrinos since it is this component that, in interacting with helium nuclei, triggers the helium flash 
B)  helium since its density has to be above a certain limit to trigger this explosive event 
C)  electrons since they control the pressure, and pressure does not depend on temperature (Under these conditions, build-up of heat can occur without leading to the normal gas expansion and the resulting thermal equilibrium.) 
D)  remnant hydrogen since loss of this component allows uncontrolled helium burning rather than a uniform rate of energy production

Question 10

How large was the Sun when it first formed as a protostar?

Accepted Answer

A)  about five times its present diameter 
B)  about fifteen times its present diameter 
C)  about fifty times its present diameter 
D)  same diameter it has now 
A)  about five times its present diameter 
B)  about fifteen times its present diameter 
C)  about fifty times its present diameter 
D)  same diameter it has now

Question 11

Protostars are:

Accepted Answer

A)  very young objects still contracting before becoming true stars. 
B)  old stars contracting after using up all of their available hydrogen fuel. 
C)  objects with less than about 0.08 solar mass that do not have enough mass to become true stars. 
D)  stars made almost entirely out of protons. 
A)  very young objects still contracting before becoming true stars. 
B)  old stars contracting after using up all of their available hydrogen fuel. 
C)  objects with less than about 0.08 solar mass that do not have enough mass to become true stars. 
D)  stars made almost entirely out of protons.

Question 12

The stars in an open cluster are useful for studying the early stages of stellar evolution because all the stars in a cluster have the same:

Accepted Answer

A)  age. 
B)  spectral type. 
C)  luminosity class. 
D)  radius. 
A)  age. 
B)  spectral type. 
C)  luminosity class. 
D)  radius.

Question 13

At what stage in its life does a star pass through the protostar phase?

Accepted Answer

A)  while it is converting hydrogen into helium in its core 
B)  when it is expanding in size as a red giant or supergiant 
C)  after nuclear reactions end in its core but before the red giant phase 
D)  after condensation but before nuclear reactions begin in its core 
A)  while it is converting hydrogen into helium in its core 
B)  when it is expanding in size as a red giant or supergiant 
C)  after nuclear reactions end in its core but before the red giant phase 
D)  after condensation but before nuclear reactions begin in its core

Question 14

Hydrogen in molecular form,H₂,is thought to be very abundant in gas clouds in space,but these molecules emit radiation relatively inefficiently since they are symmetrical.Which other molecule occurs in close association with H₂ and is used as a probe for molecular clouds?

Accepted Answer

A)  carbon monoxide (CO) 
B)  methane (CH₄) 
C)  water vapor (H₂O) 
D)  carbon dioxide (CO₂) 
A)  carbon monoxide (CO) 
B)  methane (CH₄) 
C)  water vapor (H₂O) 
D)  carbon dioxide (CO₂)

Question 15

In which location are clumps of gas MOST likely to be collapsing to form stars?

Accepted Answer

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

Question 16

Nuclear fusion reactions that convert helium into carbon and oxygen in the central core of a star occur during which phase of a star's life?

Accepted Answer

A)  in the red giant stage, before helium flash 
B)  during and immediately after the (first) red giant or supergiant stage 
C)  during the protostar stage 
D)  after the main-sequence phase, before the star becomes a red giant 
A)  in the red giant stage, before helium flash 
B)  during and immediately after the (first) red giant or supergiant stage 
C)  during the protostar stage 
D)  after the main-sequence phase, before the star becomes a red giant

Question 17

What is unusual about main-sequence stars about 75% the mass of the Sun?

Accepted Answer

A)  These stars fuse deuterium and lithium instead of hydrogen. 
B)  These stars are too small to develop any nuclear reactions. 
C)  None of these stars have yet evolved off the main sequence. 
D)  These stars develop fission rather than fusion reactions in their cores. 
A)  These stars fuse deuterium and lithium instead of hydrogen. 
B)  These stars are too small to develop any nuclear reactions. 
C)  None of these stars have yet evolved off the main sequence. 
D)  These stars develop fission rather than fusion reactions in their cores.

Question 18

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.

Question 19

Of all the low-mass red dwarfs (0.08 M < M < 0.4 M)that have formed since the Galaxy came into being 15 billion years ago,how many are presently on the main sequence?

Accepted Answer

A)  none 
B)  a few, less than 20% 
C)  most of them, more than 80% 
D)  all 
A)  none 
B)  a few, less than 20% 
C)  most of them, more than 80% 
D)  all

Question 20

The instability strip on the H-R diagram:

Accepted Answer

A)  includes part of the main sequence. 
B)  is passed through by stars on their way to the helium flash. 
C)  involves only giant stars. 
D)  is where stars erupt as novas and supernovas. 
A)  includes part of the main sequence. 
B)  is passed through by stars on their way to the helium flash. 
C)  involves only giant stars. 
D)  is where stars erupt as novas and supernovas.

Cepheid stars are:

What are the stars in the lower part of the instability strip called?

The majority of the elements heavier than hydrogen and helium in the universe are believed to have originated in:

In Earth's solar system,a nebula is believed to have formed around the early Sun.Planetesimals gradually coalesced out of this nebula and accreted to form the planets-a process requiring a total of about 100 million years.How would you describe the Sun at the end of this process?

When any star on the main sequence was a protostar,it was:

It is now believed that MOST stars are:

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

What causes the characteristic blue color of a reflection nebula?

Which component in the core of a star undergoing helium fusion leads to the behavior known as the "helium flash"?

How large was the Sun when it first formed as a protostar?

Protostars are:

The stars in an open cluster are useful for studying the early stages of stellar evolution because all the stars in a cluster have the same:

At what stage in its life does a star pass through the protostar phase?

Hydrogen in molecular form,H₂,is thought to be very abundant in gas clouds in space,but these molecules emit radiation relatively inefficiently since they are symmetrical.Which other molecule occurs in close association with H₂ and is used as a probe for molecular clouds?

In which location are clumps of gas MOST likely to be collapsing to form stars?

Nuclear fusion reactions that convert helium into carbon and oxygen in the central core of a star occur during which phase of a star's life?

What is unusual about main-sequence stars about 75% the mass of the Sun?

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

Of all the low-mass red dwarfs (0.08 M < M < 0.4 M)that have formed since the Galaxy came into being 15 billion years ago,how many are presently on the main sequence?

The instability strip on the H-R diagram:

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

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

Cepheid stars are:

What are the stars in the lower part of the instability strip called?

The majority of the elements heavier than hydrogen and helium in the universe are believed to have originated in:

In Earth's solar system,a nebula is believed to have formed around the early Sun.Planetesimals gradually coalesced out of this nebula and accreted to form the planets-a process requiring a total of about 100 million years.How would you describe the Sun at the end of this process?

When any star on the main sequence was a protostar,it was:

It is now believed that MOST stars are:

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

What causes the characteristic blue color of a reflection nebula?

Which component in the core of a star undergoing helium fusion leads to the behavior known as the "helium flash"?

How large was the Sun when it first formed as a protostar?

Protostars are:

The stars in an open cluster are useful for studying the early stages of stellar evolution because all the stars in a cluster have the same:

At what stage in its life does a star pass through the protostar phase?

Hydrogen in molecular form,H₂,is thought to be very abundant in gas clouds in space,but these molecules emit radiation relatively inefficiently since they are symmetrical.Which other molecule occurs in close association with H₂ and is used as a probe for molecular clouds?

In which location are clumps of gas MOST likely to be collapsing to form stars?

Nuclear fusion reactions that convert helium into carbon and oxygen in the central core of a star occur during which phase of a star's life?

What is unusual about main-sequence stars about 75% the mass of the Sun?

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

Of all the low-mass red dwarfs (0.08 M < M < 0.4 M)that have formed since the Galaxy came into being 15 billion years ago,how many are presently on the main sequence?

The instability strip on the H-R diagram:

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