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CH 20 HW
What is hydrostatic equilibrium in a star?
The balance between radiation from the surface and the rotation rate |
The expansion of the core when it is heated |
The balance between the force of gravity directed in and thermal pressure directed out |
The increase in the rate of fusion when the star runs out of hydrogen |
Stars release huge amounts of radiation from their surfaces while on the main sequence. Why is this necessary if a star is to maintain hydrostatic equilibrium?
If the energy were not radiated away, the balance would be upset and the star would grow larger or explode. |
It isn’t necessary. It is just a fortunate characteristic of a star. |
Fusion in the core generates huge amounts of energy which must be radiated away. |
None of the above |
A star will evolve off the main sequence when it uses up
all of its gas. |
all of its hydrogen. |
half of its hydrogen. |
most of the hydrogen in the core. |
Compared to other stars on the H-R diagram, red-giant stars are so named because they are
cooler. |
fainter. |
denser. |
younger. |
When the Sun is on the red-giant branch, it will be found at the
upper left of the H-R diagram. |
upper right of the H-R diagram. |
lower right of the H-R diagram. |
lower left of the H-R diagram. |
After the core of a Sun-like star starts to fuse helium on the horizontal branch, the core becomes
larger with time. |
dimmer with time. |
cooler with time. |
hotter with time. |
When the Sun leaves the main sequence, it will become
more massive. |
younger. |
hotter. |
brighter. |
Compared to the Sun, stars plotted near the bottom left of the H-R diagram are much
brighter. |
younger. |
more massive. |
denser. |
A white dwarf is supported by the pressure of tightly packed
protons. |
electrons. |
photons. |
neutrons. |
A star like the Sun will end up as a
binary star. |
white dwarf. |
blue giant. |
red dwarf. |
Would you expect astronomers to have more observational evidence for the evolution of Sun-like stars or high-mass stars?
Astronomers have much more observational evidence for the evolution of Sun-like stars than that of high-mass stars. |
Astronomers have much less observational evidence for the evolution of Sun-like stars than that of high-mass stars. |
On the main sequence, massive stars
conserve their hydrogen fuel by burning helium. |
evolve into stars like the Sun. |
burn their fuel more slowly than the Sun. |
burn their hydrogen fuel more rapidly than the Sun. |
Which is used observationally to determine the age of a star cluster?
the ratio of giants to supergiants |
the total number of main sequence stars |
the luminosity of the main sequence turn-off point |
the amount of dust that lies around the cluster |
the number of white dwarfs |
As a 4-10 solar mass star leaves the main sequence on its way to becoming a red supergiant, its luminosity:
first decreases, then increases. |
decreases. |
remains roughly constant. |
first increases, then decreases. |
increases. |
NoteStudied by 10 peopleNoteStudied by 41 peopleNoteStudied by 173 peopleNoteStudied by 11 peopleNoteStudied by 4 peopleNoteStudied by 4 people