nuclear reactions in the interior of a star must provide energy at a rate that equals the star's
A output of radiation
B surface temperature
C chemical composition
D age
a star ten times the mass of the sun will have a main sequence lifetime, compared to the sun's, that is
A shorter
B about the same
C longer
D dependent on additional factors
which of the following is true?
A compared to the length of a star's main sequence life, its proto star stage is relatively short in duration.
B proto stars are surrounded by cocoons of gas and dust.
C proto stars radiate mainly in the infrared.
D all of the above.
as the sun ages, the chemical composition of its core changes so that it contains a lower percentage of ______ and a greater percentage of ______.
A helium, hydrogen
B hydrogen, helium
C uranium, lead
D oxygen, carbon
which of the following is not true of red giants
A their average density is very low
B molecules are prominent in their spectra
C most are variable stars
D most are pre-main sequence stars?
when the sun goes from the main sequence to the red giant stage
A the core gets hotter and the surface gets hotter
B the core gets hotter and the surface gets cooler
C the core gets cooler and the surface gets hotter
D the core gets cooler and the surface gets cooler
as a one solar mass star evolves to the red giant stage:
A its surface temperature and its luminosity increase.
B its surface temperature and its luminosity decrease.
C its luminosity decreases and its surface temperature increases.
D its luminosity increases and its surface temperature decreases.
our knowledge of the stellar evolutionary paths on the H-R diagram is derived from
A observation of changes in stellar brightnesses with time
B calculations of models on high-speed electronic computers
C observations of the main sequence
D experiments with hydrogen, helium, and carbon fusion reactions conducted on Earth
main sequence evolution
A hydrogen shell burning.
B hydrogen core burning.
C helium shell burning.
D ejection of planetary nebula.
the kinds of thermonuclear reactions that will eventually occur in a star' core depend on its
A mass
B radius
C Doppler shift
D abundance of carbon atoms when it formed
after a star's core runs out of fuel, how does the core get to a high enough temperature to ignite the next stage of fusion reactions?
A by chemical reactions.
B by other fusion reactions.
C by gravitational contraction.
D none of these; the fusion reactions stop.
what observation leads us to the inference that stars evolve?
A they have different spectral classes.
B they have different luminosity classes.
C they have different masses.
D they shine.
E we can directly see them evolve.
the longest phase of a star's life is spent as a
A proto star
B main sequence star
C cepheid variable star
D red giant star
which of the following stars will spend the most time on the main sequence
A a 3 solar mass star
B a 10 solar mass star
C the sun
D a 0.5 solar mass star
as the sun ages it will
A continue to get smaller forever
B temporarily expand and engulf the Earth
C stay unchanged forever
D change in totally unpredictable ways
which of the following stars will have the longest lifetime (from pre-main sequence to death)
A 100 times the mass of the sun
B 10 times the mass of the sun
C sun
D one half the mass of the sun
when the core of a star shrinks after hydrogen fusion stops,
A the core cools and the star expands.
B the core cools and the star contracts.
C the core heats and the star expands.
D the core heats and the star contracts.
E Vana turns another letter.
the average time taken for energy generated by thermonuclear fusion in the center of the sun to reach the surface layers and escape is calculated to be
A about 1 billion years
B only a few seconds
C about 1 year
D about 1 million years
when a star exhausts its hydrogen, it
A becomes hotter and brighter.
B becomes cooler and brighter.
C becomes hotter and fainter.
D becomes cooler and fainter.
the reason for the above answer is that the 5mo star burns hydrogen at a ______ through the ______.
A slower rate, p-p cycle
B faster rate, cno cycle
C similar rate, triple alpha process
the evolution of a star is determined uniquely by its ______ and ______.
A size, density.
B mass, composition.
C mass, temperature.
D shape, velocity.
after a star has left the main sequence the star
A contracts throughout
B expands throughout
C contracts at the center while the surface expands
D expands at the center while the surface contracts
the helium burning phase of a given star is much shorter than its hydrogen burning phase because
A there is less helium available
B helium releases less energy per reaction
C it contracts rapidly throughout helium burning
D the star dies before it has a chance to use most of its helium
after it leaves the main sequence, which of the following would not be possible for a very massive star
A black hole
B neutron star
C supernova
D proto star
the fusion of helium to carbon in a star's core
A only takes place during the helium flash
B requires higher temperatures than the fusion of hydrogen to helium since nuclei with greater numbers of protons repel each other more strongly
C doesn't require as high a temperature as does the carbon cycle, since greater mass nuclei repel each other less strongly
D causes the star's core to become degenerate
a shell source is which of the following?
A the luminous shell of gas around a nova.
B a planetary nebula.
C a shell of fusing material such as those found around the hydrogen depleted core of post-main-sequence stars.
D a shell radiating gravitational energy around a star that has exhausted its nuclear fuel.
what is the primary difference between a star and a planet?
A age.
B mass.
C volume.
D chemical composition.
E velocity.
the temperature in the center of a post-main sequence red giant, compared to when it was on the main sequence, is
A higher
B the same
C lower
D unpredictable
which of the following stars is probably youngest
A hot main sequence star
B cool main sequence star
C red giant star
D sun
during the main sequence stage, the fuel that keeps a star like the sun shining is
A helium being converted to carbon
B hydrogen being converted to helium
C the triple-alpha process
D a large supply of free neutrons
the length of time a star spends on the main sequence is determined by its
A size
B mass
C position in the galaxy
D rate of rotation
during the main-sequence phase of its life, a star fuses
A hydrogen to helium in its core.
B hydrogen to helium in a shell.
C helium to carbon in its core.
D helium to carbon in a shell.
which of the following are old stars with no current nuclear reactions
A red giants
B main sequence stars
C white dwarfs
D proto stars
the nuclear reactions in a star's core are kept under control so long as
A the star's luminosity depends on its mass.
B the pressure of a gas depends on its temperature.
C the star's density depends on its mass.
D the star's mass depends on its temperature.
main sequence o stars are more luminous than the sun because they
A have more weight pressing on their cores.
B contain more fuel.
C have higher surface temperatures.
D have lower densities.
massive stars have short lifetimes because they
A have little available fuel
B can't sustain high enough temperatures
C are too large
D consume their fuel more rapidly
a star evolves off the main sequence when
A nuclear reactions begin in the star
B hydrogen is exhausted in the center of the star
C hydrogen is exhausted throughout the star
D the star expands overall
for a star with the sun's mass, you expect that after all the hydrogen in the core is used up, the star will next become
A a nova.
B a supernova.
C a supergiant.
D a red giant.
E a white dwarf.
which of the following is the single most important indicator of how a star will evolve?
A radius (size).
B chemical composition.
C mass.
D surface temperature.
a star which is burning hydrogen and helium in shells is probably a
A white dwarf
B main sequence star
C red giant
D binary
which of the following is not one of the four laws of stellar structure?
A hydrostatic equilibrium
B continuity of mass
C conservation of angular momentum
D energy transport
suppose a white dwarf was formed 15 billion years ago. about what must its mass be
A 100 m-sun
B 10 m-sun
C 1 m-sun
D 0.1 m-sun
a star converting hydrogen to helium in the center of the star moves in the H-R diagram as it ages
A to the main sequence
B along the main sequence
C off the main sequence
D not at all
the main sequence phase of a star's life ends when
A helium reactions begin
B hydrogen is exhausted in the center of the star
C all nuclear reactions cease permanently in the star
D hydrogen is exhausted throughout the star
which of the following stars is probably oldest
A a one solar mass main sequence star
B a one solar mass white dwarf
C a ten solar mass main sequence star
D a ten solar mass red giant
which of the following is not a necessary ingredient in the construction of a theoretical stellar model?
A a balance between gravity and gas pressure.
B a knowledge of the star's position and motion in space.
C a knowledge of the star's mass and chemical composition.
D a balance between the star's luminosity and the amount of energy generated.
which of the following stars is probably the oldest
A a main sequence star ten times more massive than the sun
B a main sequence star the same mass as the sun
C a red giant star ten times more massive than the sun
D a red giant star the same mass as the sun
which of the following is not a necessary ingredient in the construction o a theoretical star model?
A a balance between gravity and gas pressure
B a knowledge of the star's position and motion in space
C a knowledge of the star's mass and chemical composition
D a balance between the star's luminosity and the amount of energy generated
the central temperature of a star like the sun is typically
A 100 k
B 10,000 k
C 10 million k
D 10 billion k
the more massive a main sequence star is, then the
A redder it is.
B more luminous it is.
C more time it spends on the main sequence.
D greater percentage of heavy elements it contains.
the sun's source of energy at the preset time is thought to be
A the chemical burning of hydrogen gas with oxygen
B gravitational contraction
C thermonuclear fission of heavy elements into hydrogen
D thermonuclear fusion of hydrogen atoms
the factor that determines the length of a star's main sequence lifetime is the star's
A content of carbon.
B distance from the center of the galaxy.
C surface temperature.
D mass.
E spectral type.
after a star becomes a red giant, hydrogen burning
A does not occur
B occurs in the center of the core
C occurs in a shell
D occurs only during novae
why does the surface temperature of a star drop as it is evolving toward t red giant stage?
A the core is contracting and cooling
B fusion occurs in the inner core
C fusion occurs in the envelope
D the envelope is expanding
as the material in the galaxy evolves, the new stars being created would be expected
A to be mostly blue stars
B to have higher concentrations of the heavier elements
C to have lower concentrations of the heavier elements
D to have no hydrogen at all
the fundamental quality which determines a star's central pressure and temperature is
A mass
B luminosity
C surface temperature
D radius
why do stars of great mass live longer on the main sequence than stars of lesser mass?
A the massive stars have more hydrogen fuel.
B the massive stars burn their fuel more slowly.
C the massive stars go through many stages of fusion.
D more than one of the above.
E none of the above; the statement in the question is false.
what balances the force of gravity during most of the lifetime of a star
A nothing
B light
C pressure force of the gas
D relativistic forces
the evolution of stars in a binary system may differ from that of a single star because
A two stars are more massive than one star
B one star may transfer mass to the other
C two stars have a higher combined temperature than single stars
D two stars have a higher luminosity than single stars
consider two regions of the sun where the number density of the gas is the same but the temperature of one region is twice that of the other. what can you say about the gas particles of the hotter region?
A they have much more mass.
B they move around half as fast on the average.
C they move around twice as fast on the average.
D they move around four times as fast on the average.
E they collide with each other less frequently.
as a star changes from a main sequence star to become a red giant,
A it moves across the sky.
B it gets larger and cooler.
C it leaves behind remnants.
D both (a) and (b) above.
E both (a) and (c) above.
as a star becomes a red giant its core contracts because
A the temperature is decreasing
B the star is getting larger
C no energy source is available to support it
D the electrons are not yet rigid
as a star evolves toward the red giant phase its total size
A increases
B decreases
C stays about the same
D changes in unpredictable ways
which of these stars will end its main sequence lifetime most rapidly?
A a very massive star, since more massive stars consume their hydrogen more rapidly
B a low-mass star, since less massive stars have less hydrogen "fuel"
C an intermediate-mass star (like the sun), since the combination of fuel-us rate and available fuel amount peaks at spectral class g
D none of the above; stars' main sequence lifetimes are unknown
for the sun, which stage of its lifetime will be the shortest
A main sequence
B post-main sequence
C pre-main sequence
D white dwarf
most stars will spend the greatest portions of their lives in which section of the HR diagram?
A supergiant
B main sequence
C white dwarf
D red giant
E Beverly hills
an evolutionary track is
A a representation of the star's brightness and temperature at various times
B the path the star takes in the sky as it evolves
C the paths followed by hydrogen atoms as the star collapses
D the line representing the main sequence
which of the following is not considered to be one of the death stages of a star?
A black hole
B white dwarf
C t tauri
D neutron star
when during the life of a star is it smallest
A pre-main sequence
B white dwarf
C red giant
D main sequence?
when during the life of a star does it have the lowest average density
A on main sequence
B as a red giant
C as a white dwarf
D as a neutron star
an important difference between the evolution of a massive star and a 1-solar-mass star is
A the massive star has a shorter lifetime.
B the massive star does not have periods when it has hydrogen-burning or helium-burning shells.
C the massive star does not have a red giant phase.
D the massive star does not go through a wide range of temperatures over its evolution.
the two processes by which most energy is transferred from the sun's core to the photosphere are
A conduction and convection.
B radiation and convection.
C radiation and conduction.
D radiation and neutrino emission.
E neutrino emission and convection.
stars in the red-giant stage
A have small cores with low densities
B have small, high-density cores of helium or carbon
C are uniform in composition
D have large, low density cores
the sun's core temperature is roughly
A a few hundred degrees k.
B a few thousand degrees k.
C a few million degrees k.
D a few billion degrees k.
the two forces producing hydrostatic equilibrium in the sun to determine its size are
A electrical forces and gravity.
B nuclear forces and gravity.
C electrical forces and gas pressure.
D electrical forces and nuclear forces.
E gravity and gas pressure.
stars more massive than the sun obtain their energy while on the main sequence from
A the proton-proton cycle
B the cno cycle
C the triple-alpha reaction
D gravitational contraction
when a cool main sequence star has exhausted its fuel, it will become a
A neutron star
B black hole
C quasar
D white dwarf
one important source of energy in all post-main sequence stars is
A helium reactions
B hydrogen reactions in a shell
C gravity
D such stars are dead and have no source of energy
the event that marks the end of the main-sequence lifetime of a star is
A nova
B planetary nebula
C end of hydrogen burning in the core
D helium flash
the radius of the largest of the red giant stars is of the order of
A the radius of our sun
B the radius of Jupiter
C the distance from Jupiter to the sun
D the distance to the nearest star, alpha centauri
the central temperature of a star on the main sequence is about
A 10,000 deg f
B 100,000 deg f
C ten million deg f
D ten trillion deg f
on the average, how long does it take for energy created in the sun's cent to make it to the sun's surface?
A about 8 minutes
B a few hours
C a year
D about a million years
most stars will spend the greatest part of their lifetimes in which section of the H-R diagram?
A supergiant
B white dwarf
C subgiant
D red giant
E main sequence
the size of a red giant is about
A 1 light year
B 1 solar radius
C the radius of the Earth's orbit
D the radius of the Earth
when a star evolves from the main sequence
A the core gets hotter and the surface gets hotter
B the core gets hotter and the surface gets cooler
C the core gets cooler and the surface gets hotter
D the core gets cooler and the surface gets cooler
in the absence of a balancing force gravity would cause the sun to
A collapse
B explode
C no change in size would occur
D gravity would also vanish
for a star like our sun, once fusion reactions in the main- sequence phase stop, the star will next become a
A white dwarf.
B black dwarf.
C red giant.
D red supergiant.
E blue supergiant.
why do stars age?
A all things must age and stars are just following the natural way.
B the gravitational collapse of a star must eventually reach its limit.
C all stars have a finite amount of fuel and it eventually runs out.
D astronomers really do not know why stars age.
the greatest difference between the evolution of a 5 solar mass star and that of a 1 solar mass star is that
A the 5 solar mass star never burns helium.
B the 5 solar mass star stays on the main sequence forever.
C the 5 solar mass star evolves much more quickly.
D the 5 solar mass star evolves much more slowly.
after hydrogen fusion stops in a massive star's core, the core
A collapses until helium fusion begins within it.
B collapses until it cools to a cinder.
C expands and heats until it causes helium fusion around it.
D expands and heats until helium fusion begins within it.
E expands and cools.
the nuclear reactions in a star's core remain under control so long as
A luminosity depends on mass
B pressure depends on temperature
C density depends on mass
D weight depends on temperature
when a star reaches a stable condition where the outward pressure of fusion balances the inward pressure of gravity, astronomers say that the star
A reaches the red giant stage
B reaches the brown dwarf stage
C reaches the main sequence
D will stop evolving
thermal equilibrium is
A the fusion of hydrogen to form helium
B the contraction of matter to form stars
C chemical conversion to form heavy elements
D the balance between the inflow and outflow of radiant energy inside a star
for stars on the main sequence there is a direct correlation between mass and
A luminosity
B composition
C velocity
D iron abundance
the density in the center of an old red giant is
A much less than that of water
B about the same as that of water
C much greater than that of water
D undefinable
there is a relation between the masses of stars and their
A volumes
B densities
C distances from us
D brightnesses
on the H-R diagram, a star spends most of its lifetime
A getting to the main sequence.
B on the main sequence.
C as a variable.
D as a red giant.
which of the following occurs during the phase of the hydrogen burning she
A the core shrinks until the star becomes a white dwarf
B the core temperature decreases while the envelope temperature increases
C the star becomes a supernova
D the envelope expands and cools, and the star becomes a red giant
a star evolves off the main sequence when
A all of its hydrogen has been depleted
B the hydrogen in the central, high temperature region has been depleted
C the temperature in the central region drops too low
D the force of gravity becomes too weak
the life of a 5mo is ______ that of a 1mo star.
A longer than
B shorter than
C equal to
a star evolves off the main sequence when
A hydrogen is exhausted in the core of the star
B hydrogen is completely exhausted throughout the star
C helium reactions begin in the center of the star
D the star dies
a star like the sun will have _____ percent of its mass in the form of heavy elements (elements heavier than hydrogen or helium)
A 1 (traces of heavier elements)
B 10
C 30
D 50
in the thermonuclear process which is thought to heat the sun, which nuclei of chemical elements are converted to other nuclei to produce the requisite energy?
A hydrogen to helium
B iron, in a chain reaction, eventually to hydrogen
C uranium to lead
D helium to hydrogen
a red giant is most likely getting its energy from
A gravity
B helium reactions alone
C hydrogen and helium reactions
D degenerate reactions
which one of the following is true about two stars of different mass?
A the more massive star survives longer because it has more fuel
B the less massive star survives longer because it actually has more usable hydrogen in its core
C the less massive star survives longer because it uses a different chain reaction chain than the more massive one
D the less massive star survives longer because it uses its fuel at a slower rate
the sun generates energy in the ______ through the process of______
A corona, nuclear fission.
B core, gravitational collapse.
C corona, triple alpha process.
D core, nuclear fusion.
red giant stars are large because
A nuclear reactions are occurring at the surface
B the core has contracted
C little insulating material remains between the surface layers and the nuclear reactions
D gravity has weakened
a star near the lower end of the main sequence gets most of its energy from
A gravitational contraction
B the proton-proton chain
C the carbon cycle
D the triple alpha process.
star a and star b compose a visual binary star. star a is a white dwarf w a mass of 1.2 solar masses. star b is a main sequence star with a mass 2 times the sun's. which of the following is true?
A star a is older than star b
B star a must be less massive now than it once was
C star a will eventually explode as a supernova
D the mass measurement must be wrong
fusion in the core of a stable massive star cannot proceed beyond iron because:
A that requires temperatures even stars cannot generate.
B iron nuclei are the most tightly bound of all nuclei so fusion does not release energy.
C iron is the "ultimate" element.
D the chandrasekhar limit has been reached.
consider two main-sequence stars that have different masses. you can correctly infer that the more massive star will have a
A lower luminosity and shorter lifetime.
B higher luminosity and shorter lifetime.
C higher luminosity and longer lifetime.
D lower luminosity and longer lifetime.
the properties of a star at any given age depend completely upon the star'
A luminosity and radius
B mass and luminosity
C mass, chemical composition, and radius
D mass and chemical composition
the main sequence lifetime of a star ten times more massive than the sun, compared to the main sequence lifetime of the sun, is
A much shorter
B slightly shorter
C about the same
D much longer
the most massive stars, when they first become stable are usually
A hot and luminous
B cool and dim
C cool and luminous
D any of the above
what occurs immediately following the main sequence phase of a star's life
A hydrogen shell burning
B helium flash
C overall contraction of the star
D contraction on the inside but expansion on the outside?
which of the following lists the stages in a star's life in correct order?
A main sequence, proto star, white dwarf, red giant.
B proto star, red giant, main sequence, white dwarf.
C proto star, main sequence, white dwarf, red giant.
D white dwarf, proto star, main sequence, red giant.
E proto star, main sequence, red giant, white dwarf.
why do massive stars run out of hydrogen in their cores faster than less massive stars?
A their hydrogen fuses faster because of greater pressure.
B there is less hydrogen in their cores.
C the cores of less massive stars contain a greater percentage of helium, which slows hydrogen fusion.
D the cores of less massive stars contain a lesser percentage of helium, which slows hydrogen fusion.
E the statement is false; more massive stars do not run out of hydrogen faster than stars of
less mass.
if the rate of hydrogen fusion within the sun were to increase somehow, the core would
A collapse and the sun would grow cool.
B collapse and heat up further.
C expand and therefore tend to slow the fusion.
D expand and therefore increase in temperature.
E stay the same size but become hotter.
after the sun's core hydrogen is depleted the core will consist primarily of:
A carbon.
B deuterium.
C helium.
D oxygen.
which of the following stars has the shortest total lifetime from birth to death
A a cool main sequence star
B a supernova
C a white dwarf
D a red giant in an old cluster
which of the following is always occurring during the life cycle of all stars
A nuclear reactions are occurring in the center of the star
B nuclear reactions are occurring somewhere in the star
C the force of gravity attempts to force the contraction of the star
D the star is getting smaller
Sirius is a double star. the component designated Sirius a is an a type stars of 2 solar masses. Sirius b is a white dwarf with half that much mass. we presume that
A Sirius b has always been of lower mass than Sirius a and has never been ve bright
B Sirius b was originally the more massive and more luminous of the pair
C Sirius b was originally of low mass but very high luminosity
D Sirius b has been formed by material ejected from Sirius a and hence is a younger star
the main sequence life of a star ends when
A the star runs complete out of hydrogen.
B hydrogen fusion stops in the core.
C helium fusion stops in the core.
D the star cools down so much that fusion can no longer take place.
E two of the above.
compared to cool main sequence stars, hot main sequence stars have lifetimes that are
A longer
B shorter
C about the same
D dependent on other factors
what causes a star to swell up as a red giant?
A increased energy produced within it.
B a decrease in the energy produced within it.
C the nearby passage of a massive star.
D the formation of a cocoon around it.
a stellar model is
A useful in studying the interiors of stars.
B useful in studying the evolution of stars.
C a table of numbers.
D all of these.
basically, stars evolve because they
A are made of hydrogen.
B are gases.
C give off energy.
D are larger than planets.
E none of the above.
comparing the lives of stars of different masses, we can conclude that
A more massive stars probably never burn helium.
B less massive stars spend less time in hydrogen-burning phases.
C more massive stars evolve faster.
D less massive stars are likely to become giant stars sooner than stars with greater mass.
the sun
A has contracted in the past, before fusion began
B will probably remain a main sequence star about 5 million more years
C will never be any larger than it is now
D is likely to become a supernova rather than a white dwarf when it dies
the main sequence exists because
A a given star spends most of its life at one place in the H-R diagram
B stars move up the main sequence as they age
C stars move down the main sequence as they age
D stars are not allowed to move below it
as a gas is heated, it will
A expand
B contract
C neither expand nor contract
D oscillate
normal chemical reactions cannot explain the amount of energy released by stars because
A stars are not made of normal chemical elements
B stars are too hot for such reactions to occur
C chemical reactions release too little energy to explain the amount of energy released by stars
D none of the above
a star's core does not contract while
A it is a proto star
B it is undergoing fusion
C it is producing hydrogen from helium
D it is evolving toward the red giant stage
stars evolve because of changes in
A chemical composition of the core
B luminosity of the star
C mass of the star
D chemical composition of the surface
hydrogen burning for a sun-like star lasts approximately
A ten million years
B one hundred million years
C one billion years
D ten billion years
since the gravity of the outer layers pressing in is equal to the pressure set up by the gas inside the sun, we say that our star is in a state of
A hydrostatic equilibrium
B thermal convection
C radiative diffusion
D differential rotation
stars on the upper end of the main sequence next evolve into
A lower main sequence stars
B solar-type stars
C white dwarfs
D red giants
the minimum mass for main-sequence stars is set by
A the minimum mass fragments of star-forming nebulae
B the mass-luminosity relation
C the ignition temperature of hydrogen
D the density requirements of the carbon cycle
the sun
A has a predicted main sequence lifetime of about ten billion years and thus will remain about as it is for another ten billion years
B has a predicted main sequence lifetime of about five billion years and thus will remain about as it is for another five billion years
C has a predicted main sequence lifetime of about ten billion years, roughly half of which is over
D will become a main sequence star in about 4.6 billion years
when a solar-mass star exhausts the hydrogen in its core, it will move on an HR diagram to the
A upper right
B lower right
C upper left
D lower left
the primary property that influences the kind of death a star will experience is its
A diameter
B temperature
C color
D mass
when the core hydrogen has been converted to helium, the core will next
A collapse
B expand
C burn helium
D decrease in temperature
the total time which the sun will spend as a main sequence star is
A about 4.5 million years
B about 10 billion years
C about 1 million years
D at least 200 billion years
the force of gravity is continually trying to change a star as follows
A make it larger
B make it smaller
C make it cooler
D none of these
which of the following objects does not represent the end-point of a star' evolutionary life?
A neutron star
B supernova
C red giant
D black hole
the evolution of a star depends primarily on the star's
A radius
B mass
C luminosity
D density
when a star exhausts its central hydrogen, it
A becomes hotter and brighter
B becomes cooler and brighter
C becomes hotter and fainter
D becomes cooler and fainter
the evolution of a star depends predominantly upon
A its surface temperature
B its location in the galaxy
C its chemical composition
D its initial mass
the longest stage in the life cycle of a star is
A red giant
B proto star
C black hole
D main sequence
a 1 solar mass star eventually dies because
A it cannot burn hydrogen
B it cannot burn helium
C it is so dense that it must "shrink"
D its nuclear reactions cease
when a star runs out of hydrogen fuel in its core
A its burned-out hydrogen contracts until the protons stick together to form helium nuclei
B its helium core contracts, causing the star to shrink
C its helium core contracts, causing the rest of the star to expand and become a red giant
D the "turnoff point" is reached, since hydrogen fusion has been "turned off
what is an evolutionary track?
A the path of a star through space
B a dark filamentary feature on the surface of a star
C a graph of temperature at various positions inside a star
D the sequence of positions in the H-R diagram that the star occupies as it undergoes
evolutionary changes
a nova explosion is
A a small-scale supernova explosion
B the source of the "crab nebula"
C temporary fusion reactions on the surface of a white dwarf star in a binary system
D temporary fusion reactions on the surface of a solitary white dwarf star
new red giant stars generate their energy from
A overall collapse of the star
B helium reactions in the core
C hydrogen reactions in a shell around the core
D both b and c
the factor that determines a star's main sequence lifetime is the star's
A content of carbon
B distance from the center of the galaxy
C surface temperature
D mass
a star like the sun will spend the largest fraction of its life
A contracting from an interstellar cloud
B as a main sequence star
C as a red giant
D as a planetary nebula
a compelling reason for stating that a hot, bright star must be relatively young is that such a star
A is giving out enough light to illuminate its birth processes
B is using up fuel at a great rate and cannot exist for long
C is bright because of friction with other bodies in the region from which it came
D is pulsating
hot main sequence stars are more luminous than the sun because they
A have stronger gravity pressing on their cores
B contain more fuel
C have higher surface temperatures
D have lower densities
at the present time, the energy of the sun is generated
A throughout the sun, by gravitational collapse
B in the center by fusion of helium nuclei, and in an outer shell by fusion of hydrogen nuclei
C in its center only, by fusion of hydrogen nuclei
D in its center only, by fission of heavy nuclei
from its initial position on the main sequence, the sun will
A move to the upper left along the main sequence
B move to the lower right along the main sequence
C move directly to the white dwarf region of the H-R diagram
D become a red giant
during the time a star fuses hydrogen into helium in its core its position on the H-R diagram is
A above and to the left of the main sequence
B on the main sequence
C in the area of the red giants
D among the white dwarfs
although we don't see most stars change very much, we know that stars must evolve because
A all stars do not look the same
B objects on Earth age, so objects in space must also age
C stars lose energy to space
D the HR diagram shows evolutionary paths of stars
hydrostatic equilibrium is an equilibrium between
A hydrogen and carbon
B water, hydrogen, and oxygen
C gravity and outward pressure
D water and electric (static) charge
if the interior temperature of a main sequence star decreases, the interior of the star will
A do nothing - that is, remain the same
B contract
C expand
D explode
in a star,
A the gas is densest in the core
B the gas is densest near the surface
C the temperature is hottest at its surface
D hydrogen in produced by the thermonuclear burning of helium
as a star ages, the chemical makeup of its interior changes. what happens to the chemical makeup of the outside?
A we have no way of finding out
B the chemical makeup of the outside changes very little
C the same changes occur on the outside as on the inside
D the outside becomes richer in hydrogen
giant and supergiant stars are rare because
A they do not form as often as main-sequence stars
B the giant and supergiant stage is unstable
C the giant and supergiant stage is very short compared to the main sequence stage
D helium is very rare
for a star with the sun's mass, you expect that after all the hydrogen in the core is used up, the star will next become
A a nova
B a supernova
C a red giant
D a white dwarf
the increase in apparent brightness of a nova
A is about a factor of 2
B is about a factor of 1000
C is about a factor of 100,000,000
D depends on the distance.
the helium burning phase of a star's life is relatively short because
A very little of the helium is used
B the temperature never rises high enough for complete helium burning
C most of the helium is consumed in the helium flash
D each reaction of the helium releases much less energy than a hydrogen reaction.
which of the following conditions is not necessary for a nova
A an aged star
B a star less massive than the sun
C a binary star
D a star contracting toward the white dwarf stage.
which of the following objects undergo a relatively mild surface explosion
A cepheid variable
B red giant variable
C nova
D supernova?
the helium flash occurs when
A hydrogen first becomes exhausted in the center
B catastrophic gravitational collapse of the star is reversed
C helium reactions begin in the center
D extra hydrogen is added to the surface
the helium flash occurs because
A fusion of helium releases much more energy than other reactions
B the rigid structure of the electrons does not allow the star to readjust
C the star has become so large that it collapses violently
D the intermediate product of the helium reactions is unstable.
cepheid variables are located
A on the main sequence
B below the main sequence
C above the main sequence
D in no particular place in the H-R diagram.
the relative number of stars observed in different parts of the H-R diagram is a measure of
A their ages
B their mass
C the length of time stars spend in different parts of the diagram
D the number of stars which are currently forming in the galaxy
as the sun ages it will eventually
A throw off its outer layers to form a planetary nebula
B explode into a violent supernova
C contract into a black hole
D remain the same forever
the major source of energy in a "typical" cepheid variable is
A gravitational contraction
B hydrogen reactions at the center
C hydrogen reactions in a shell
D electrons in a magnetic field.
the helium flash is
A a flash of light seen when helium begins to react in a star
B an explosion at the center of a star which is not seen at the surface
C the explosion which leads to the formation of a planetary nebula
D the flash seen when a star disappears into a black hole
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