7233083
Questão 1
Questão
As a star exhausts the hydrogen in its core, what happens?
Responda
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It becomes hotter and more luminous
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It becomes hotter and less luminous
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It becomes cooler and less luminous
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It becomes cooler and more luminous
Questão 2
Questão
When does a star experience helium fusion?
Responda
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just before it enters the main sequence
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after it has become a red giant star
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when it is on the horizontal branch
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before it leaves the main sequence
Questão 3
Questão
Why are giant and supergiant stars rare?
Responda
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The giant and supergiant stages are very short
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The star blows up before the giant or supergiant stage is reached
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They do not form as often as main sequence stars
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The giant or supergiant stage is very long
Questão 4
Questão
Which of the following statements best describes why stars eventually die?
Responda
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Their lifespan is limited
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They exhaust all their fuel
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Their cores become hotter
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They become less luminous
Questão 5
Questão
Which of the following occurs during the giant stage?
Responda
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helium fusion in the core and hydrogen fusion in the surrounding shell
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hydrogen fusion in the core and helium fusion in the surrounding shell
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hydrogen and helium fusion in the core
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hydrogen flash
Questão 6
Questão
In what way are giants and supergiants similar?
Responda
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They are the main sequence stars
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They undergo a helium flash stage as they enter the main sequence
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They are very luminous
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Their cores expand rapidly to reach giant sizes
Questão 7
Questão
What is the term for a collection of 105 to 106 old stars in a region 30 to 100 light-years in diameter?
Responda
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Herbig-Haro object
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globular cluster
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open cluster
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giant cluster
Questão 8
Questão
What is the defining characteristic of stars within a cluster that are at the turnoff point?
Responda
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They are just leaving the main sequence
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They are just becoming white dwarfs
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They are just entering the main sequence
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They are about to explode in supernovae
Questão 9
Questão
What is the approximate age of the star cluster in the H-R diagram? (Hint: Main sequence stars of spectral types O and B have a core supply of hydrogen that is sufficient to last about 250 million years; types A and F, about 2 billion years; type G about 10 billion years; types K and M about 30 billion years. The apparent magnitude scale means that larger numbers are toward the bottom of the vertical axis.)
Responda
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200 million years
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2 billion years
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10 billion years
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30 billion years
Questão 10
Questão
Refer to the H-R diagram. What type of star do the two data points above spectral type “A” represent?
Responda
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massive main sequence stars
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massive supergiant stars
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white dwarfs with mass less than the sun’s mass
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white dwarfs with mass greater than twice the sun’s mass
Questão 11
Questão
Refer to the H-R diagram. What type of star do the data points above spectral type “M” represent?
Responda
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massive main sequence stars
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massive main sequence stars with mass less than the sun’s mass
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main sequence stars with luminosities higher than the sun’s luminosity
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pre-main sequence stars
Questão 12
Questão
Refer to the H-R diagram. How would the H-R diagram of an older star cluster look different
Responda
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The points would shift to the right, because all of the stars would have lower temperatures
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The lower main sequence would look the same, but the turnoff would be at spectral type K or M
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The points would shift down, because all of the stars would have lower luminosities
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The lower main sequence would look the same, but the turnoff would be at spectral type F or A
Questão 13
Questão
Refer to the H-R diagram. How would the H-R diagram of a more distant star cluster look different?
Responda
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The points would shift down, because all of the stars would have larger apparent magnitudes
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The points would shift to the right, because all of the stars would appear to be cooler
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The points would shift up, because all of the stars would have smaller apparent magnitudes
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The points would shift to the left, because all of the stars would appear to be hotter
Questão 14
Questão
Which nuclear fuels does a one solar mass star use over the course of its entire lifespan?
Responda
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hydrogen
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hydrogen and helium
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hydrogen, helium, and carbon
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hydrogen, helium, carbon, and oxygen
Questão 15
Questão
Star A is a 1 solar mass white dwarf, and star B is a 1.3 solar mass white dwarf. How would they differ?
Responda
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Star A has a smaller radius
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Star B has a smaller radius
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Star B is supported by neutron degeneracy pressure
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Star A is hotter
Questão 16
Questão
What is the source of the energy radiated by a white dwarf?
Responda
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the proton-proton chain
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the CNO cycle
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gravitational contraction after becoming a white dwarf
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gravitational contraction during the white dwarf formation phase
Questão 17
Questão
What does the Chandrasekhar-Landau limit tell us?
Responda
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Accretion disks can grow hot through friction
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Neutron stars of more than 3 solar masses are not stable
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White dwarfs more massive than 1.4 solar masses are not stable
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Stars with a mass less than 0.5 solar masses will not go through helium flash
Questão 18
Questão
What is the ultimate fate of our Sun?
Responda
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It will become a neutron star
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It will explode in a supernova
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It will become a white dwarf
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It will explode in a nova
Questão 19
Questão
Which scenario is most likely to happen when the Sun enters the red giant stage?
Responda
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Mercury, Venus, and Earth will be destroyed by the expanding Sun
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Mercury will be destroyed by the expanding Sun, but Venus and Earth will remain intact
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The Sun will engulf and destroy all planets in the Solar System
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The Sun will never expand far enough to reach Mercury or any other planets in the Soar System
Questão 20
Questão
If the stars at the turnoff point of a cluster have a mass of 3 times the mass of the Sun, what is the age of the cluster?
Responda
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6.4×10^8 years
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3.3×10^9 years
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3.0×10^10 years
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1.6×10^11 years
Questão 21
Questão
Which of the following correctly describes a relationship between pressure, temperature, and density in degenerate matter?
Responda
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Pressure depends only on the temperature
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Pressure does not depend on temperature
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Temperature depends only on density
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Pressure does not depend on density
Questão 22
Questão
What is a white dwarf composed of?
Responda
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hydrogen nuclei and degenerate electrons
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helium nuclei and normal electrons
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carbon and oxygen nuclei and degenerate electrons
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degenerate iron nuclei
Questão 23
Questão
As a white dwarf cools, its radius remains the same. Why is this?
Responda
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because pressure due to nuclear reactions in a shell just below the surface keeps it from collapsing
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because pressure does not depend on temperature for a white dwarf, since the electrons are degenerate
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because pressure does not depend on temperature, since the star has exhausted all its nuclear fuels
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because material accreting onto it from a companion maintains a constant radius
Questão 24
Questão
What are the two longest stages in the life of a one solar mass star?
Responda
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protostar, pre–main sequence
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protostar, white dwarf
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protostar, main sequence
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main sequence, white dwarf
Questão 25
Questão
Which of the following is the most important factor that determines a life cycle of a star (for example, why some stars have a short life span)?
Responda
-
mass
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temperature
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luminosity
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radius
Questão 26
Questão
What principle explains why matter flowing from one star in a binary system to its companion forms an accretion disk?
Responda
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conservation of tidal forces
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conservation of temperature
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conservation of angular momentum
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conservation of energy
Questão 27
Questão
Suppose you discover a binary star system with a 0.7 solar mass giant star and a 2 solar mass main sequence star. Why is this surprising?
Responda
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0.7 solar mass stars are not expected to become giants
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All 2 solar mass stars should have left the main sequence
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Giant stars are expected to destroy their companions, so the 2 solar mass star shouldn’t exist
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The 2 solar mass star should have become a giant before the 0.7 solar mass star
Questão 28
Questão
When material expanding away from a star in a binary system reaches the edge of its Roche lobe, what happens?
Responda
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The material will start to fall back toward the star
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All of the material will accrete on to the companion
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The material will no longer be gravitationally bound to the star
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The material will increase in temperature and eventually undergo thermonuclear fusion
Questão 29
Questão
When mass is transferred toward a white dwarf in a binary system, the material forms a rapidly growing whirlpool of material. What is that whirlpool called?
Responda
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an accretion disk
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an Algol paradox
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a planetary nebula
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a supernova remnant
Questão 30
Questão
Under what conditions are Type Ia supernovae believed to occur?
Responda
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when the core of a massive star collapses
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when a white dwarf exceeds the Chandrasekhar-Landau limit
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when hydrogen detonation occurs
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when neutrinos in a massive star form a shock wave that explodes the star
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