Stars with masses below a certain threshold produce most of their energy via the proton-proton chain. What is that threshold?
0.01 solar masses
0.1 solar masses
1.1 solar masses
11 solar masses
Which of the following is considered to be the best explanation for the missing solar neutrinos?
The Sun is fusing helium but not hydrogen
Nuclear reactions do not produce neutrinos as fast as theory predicts
The Sun may contain matter we haven't yet identified
Neutrinos may oscillate between three different flavours
How did observations at the Sudbury Neutrino Observatory solve the solar neutrino problem?
They showed that the “missing neutrinos” had changed into a different type
They showed that other experiments had miscounted the number of solar neutrinos
They showed that models for the number of neutrinos produced by the Sun were wrong
They showed that neutrinos were not escaping from the core of the Sun
Why does the main sequence have a limit at the lower end?
Low mass stars form from the interstellar medium very rarely
Low mass objects are composed primarily of solids, not gases
The lower limit represents a star with zero radius
A minimum temperature is required for hydrogen nuclear fusion to take place
Why is there a main sequence mass-luminosity relation?
because helium fusion produces carbon
because more massive stars support their larger weight by making more energy
because the helium flash occurs in degenerate matter
because all stars on the main sequence have about the same radius
What is the approximate mass of the lowest mass object that can initiate the thermonuclear fusion of hydrogen?
0.08 solar mass
1 solar mass
8 solar masses
80 solar masses
Which of the following is most similar in size to a brown dwarf?
the planet Jupiter
a red dwarf
a white dwarf
a Bok globule
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?
brown dwarfs
Herbig-Haro objects
Bok globules
T Tauri stars
What would happen if the nuclear reactions in a star began to produce too much energy?
The star would shrink
The star would expand
The star would collapse
Nothing would happen
How much of its lifetime does the average star spend on the main sequence?
1%
10%
20%
90%
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?
the zero-age main sequence
the birth line
the Coulomb barrier
the evolutionary track
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?
1
2
3
4
Refer to the H-R diagram. Which point represents a star in which the proton-proton chain is occurring?
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?
1.8×10^6 years
1.8×10^9 years
1.8×10^10 years
1.8×10^11 years
What type of star is our Sun?
intermediate-mass star
yellow giant
low-mass star
high-mass star
What is the lifetime of a 10 solar mass star on the main sequence?
3.2×10^7 years
1×10^9 years
1×10^11 years
3.2×10^12 years
What characteristic of a star primarily determines its location on the main sequence?
age
distance from the galactic centre
mass
radius
In which option below are the stellar types sorted from shortest to longest main-sequence lifetime?
O, A, K, M
A, B, F, G
K, F, B, O
B, A, M, G
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?
Star 2 has more helium in its core and a hotter surface
Star 2 has more helium in its core and a cooler surface
Star 1 is more luminous and has a hotter surface
Star 1 is more luminous and has a cooler surface
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