7232949
Questão 1
Questão
Stars with masses below a certain threshold produce most of their energy via the proton-proton chain. What is that threshold?
Responda
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0.01 solar masses
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0.1 solar masses
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1.1 solar masses
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11 solar masses
Questão 2
Questão
Which of the following is considered to be the best explanation for the missing solar neutrinos?
Responda
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The Sun is fusing helium but not hydrogen
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Nuclear reactions do not produce neutrinos as fast as theory predicts
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The Sun may contain matter we haven't yet identified
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Neutrinos may oscillate between three different flavours
Questão 3
Questão
How did observations at the Sudbury Neutrino Observatory solve the solar neutrino problem?
Responda
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They showed that the “missing neutrinos” had changed into a different type
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They showed that other experiments had miscounted the number of solar neutrinos
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They showed that models for the number of neutrinos produced by the Sun were wrong
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They showed that neutrinos were not escaping from the core of the Sun
Questão 4
Questão
Why does the main sequence have a limit at the lower end?
Responda
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Low mass stars form from the interstellar medium very rarely
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Low mass objects are composed primarily of solids, not gases
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The lower limit represents a star with zero radius
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A minimum temperature is required for hydrogen nuclear fusion to take place
Questão 5
Questão
Why is there a main sequence mass-luminosity relation?
Responda
-
because helium fusion produces carbon
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because more massive stars support their larger weight by making more energy
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because the helium flash occurs in degenerate matter
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because all stars on the main sequence have about the same radius
Questão 6
Questão
What is the approximate mass of the lowest mass object that can initiate the thermonuclear fusion of hydrogen?
Responda
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0.08 solar mass
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1 solar mass
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8 solar masses
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80 solar masses
Questão 7
Questão
Which of the following is most similar in size to a brown dwarf?
Responda
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the planet Jupiter
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a red dwarf
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a white dwarf
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a Bok globule
Questão 8
Questão
Which of the following are star-like objects that contain less than 0.08 solar masses and will never raise their core temperatures high enough that the proton-proton chain can begin?
Responda
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brown dwarfs
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Herbig-Haro objects
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Bok globules
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T Tauri stars
Questão 9
Questão
What would happen if the nuclear reactions in a star began to produce too much energy?
Responda
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The star would shrink
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The star would expand
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The star would collapse
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Nothing would happen
Questão 10
Questão
How much of its lifetime does the average star spend on the main sequence?
Responda
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1%
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10%
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20%
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90%
Questão 11
Questão
The lower edge of the main-sequence band represents the location in the H-R diagram at which stars begin their lives as main-sequence stars. What is it called?
Responda
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the zero-age main sequence
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the birth line
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the Coulomb barrier
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the evolutionary track
Questão 12
Questão
On the H-R diagram, the line indicates the location of the main sequence. Which of the four labeled locations on the H-R diagram indicates a luminosity and temperature similar to that of a T Tauri star?
Responda
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1
-
2
-
3
-
4
Questão 13
Questão
Refer to the H-R diagram. Which point represents a star in which the proton-proton chain is occurring?
Responda
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1
-
2
-
3
-
4
Questão 14
Questão
The Sun has an expected main-sequence lifetime of about 10^10 years. What is the lifetime on the main sequence of a 2 solar mass star?
Responda
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1.8×10^6 years
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1.8×10^9 years
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1.8×10^10 years
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1.8×10^11 years
Questão 15
Questão
What type of star is our Sun?
Responda
-
intermediate-mass star
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yellow giant
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low-mass star
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high-mass star
Questão 16
Questão
What is the lifetime of a 10 solar mass star on the main sequence?
Responda
-
3.2×10^7 years
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1×10^9 years
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1×10^11 years
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3.2×10^12 years
Questão 17
Questão
What characteristic of a star primarily determines its location on the main sequence?
Responda
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age
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distance from the galactic centre
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mass
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radius
Questão 18
Questão
In which option below are the stellar types sorted from shortest to longest main-sequence lifetime?
Responda
-
O, A, K, M
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A, B, F, G
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K, F, B, O
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B, A, M, G
Questão 19
Questão
Consider two stars of the same mass: star 1 has just moved on to the main sequence, and star 2 is about to leave it. How are these two stars different?
Responda
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Star 2 has more helium in its core and a hotter surface
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Star 2 has more helium in its core and a cooler surface
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Star 1 is more luminous and has a hotter surface
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Star 1 is more luminous and has a cooler surface
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