Which two processes can generate energy to help a star maintain its internal thermal pressure?
Nuclear fusion and gravitational contraction
Our Sun is considered to be a ______.
Which process is required to allow a gravitationally-collapsing gas cloud to continue to collapse?
The cloud must radiate much of its thermal energy
Angular momentum plays an important role in star formation. Which of the following characeristics of a protostellar system is probably not strongly affected by the star's angular momentum?
The onset of core hydrogen fusion
Generally speaking, how does the surface temperature and luminosity of a protostar compare to the surface temperature and luminosity of the main-sequence star it becomes?
The main-sequence star is hotter and dimmer than it was as a protostar
Consider a large molecular cloud that will give birth to a cluster of stars. Which of the following would you expect to be true?
A few massive stars will form, live, and die before the majority of the star's clusters even complete their protostar stage.
We do not know for certain whether the general trends we observe in stellar birth masses also apply to brown dwarfs. But if they do, then which of the following would be true?
Brown dwarfs would outnumber all ordinary stars
Where would a brown dwarf be located on an H-R diagram?
below and to the right of the lowest part of the main sequence
Which of the following types of data provide evidence that helps us understand the life tracks of low-mass stars?
H-R diagrams of globular clusters
Why is a 1 solar-mass red giant more luminous than a 1 solar-mass main sequence star?
Fusion reacions are producing energy at a greater rate in the red giant
Carbon fusion occur in high-mass stars but not in low-mass stars because ________.
The cores of low-mass stars never get hot enough for carbon fusion
Which of the following statements about various stages of core nuclear burning (hydrogen, helium, carbon, and so on) in a high-mass star is not true?
Each successive stage lasts for approximately the same amount of time.
Which event marks the beginning of a supernova?
The sudden collapse of an iron core into a compact ball of neutrons
Suppose that the star Betelgeuse (the upper left shoulder of Orion) were to supernova tomorrow (as seen here on Earth). What would it look like to the naked eye?
Betelgeuse would remain a dot of light, but would suddenly become so bright that, for a few weeks, we'd be able to see this dot in the daytime.
Observations show that elements with atomic mass numbers divisible by 4 (such as oxygen-16, neon-20, and magnesium-24) tend to be more abundant in the universe than elements with atomic mass numbers in between. Why do we think this is the case?
At the end of a high-mass star's life, it produces new elements through a series of helium capture reactions.
A spinning neutron star has been observed at the center of a _________.
Which is more common: a star blows up as a supernova, or a star forms a planetary nebula/white dwarf system?
Planetary nebula formation is more common
You discover a binary star system in which one star is a 15 MSun main-sequence star and the other is a 10 MSun giant. How do we think that a star system such as this might have come to exist?
The giant must once have been the more massive star, but is now less massive because it transferred some of its mass to its companion.