Chapter 12 Flashcards
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 ________.
low mass star
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 characteristics of a protostellar system is probably not strongly affected by the star's angular momentum? the onset of core hydrogen fusion the formation of a protostellar disk the existence of protostellar jets the strength of protostellar winds
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?
A 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?
All the stars in the cluster will be of about the same mass.
A few massive stars will form, live, and die before the majority of the star’s clusters even complete their protostar stage.
All the stars in the cluster will become main-sequence stars at about the same time.
All the stars in the cluster will have approximately the same luminosity and surface temperature.
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?
observing a low-mass star over many years
H-R diagrams of open clusters
spacecraft observations of the Sun
H-R diagrams of globular clusters
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 reactions 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.
As each stage ends, the reactions that occurred in previous stages continue in shells around the core.
As each stage ends, the core shrinks and heats further.
Each successive stage creates an element with a higher atomic number and atomic mass number.
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.
