What do astronomers mean when they say that we are all "star stuff"?
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that the carbon, oxygen, and all elements heavier than helium that are essential to life were created by nucleosynthesis in stellar cores
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Sun is considered to be a
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low-mass star.
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In the context of understanding stellar lives, "high-mass" stars have masses
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more than 8 solar masses
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In the context of understanding stellar lives, "low-mass" stars have masses
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less than 2 solar masses
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Of the listed below, which star will live longest?
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a 1 solar-mass star
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Which of the following is not involved in carrying energy outward from a main sequence star's core
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conduction
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Which stars have convective cores?
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high-mass stars
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During main sequence phase if its life star's
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Luminosity, temperature, and radius gradually increase.
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What happens when a star exhausts the hydrogen in its core?
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Its core contracts, but its outer layers expand and the star becomes bigger and brighter.
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What is happening inside a star while it expands into a subgiant?
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It is fusing hydrogen into helium in a shell outside the core.
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The main source of energy for a star as it grows in size to become a red giant is
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hydrogen fusion in a shell surrounding the central core.
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Why does a star grow larger after it exhausts its core hydrogen?
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Hydrogen fusion in a shell outside the core generates enough thermal pressure to push the upper layers outward.
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Compared to the star it evolved from, a red giant is
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cooler and brighter.
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Why is a 1 solar mass red giant more luminous than a 1 solar mass main sequence star?
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Fusion reactions are producing energy at a greater rate in the red giant.
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Which of the following pairs of atomic nuclei would feel the strongest repulsive electromagnetic force if you tried to push them together?
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helium and helium
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What is a helium flash?
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The sudden onset of helium fusion in the core.
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The helium fusion reaction (triple alpha process)
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combines three helium nuclei fuse to form one carbon nucleus.
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At approximately what temperature can helium fusion occur?
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100 million K
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What happens right after a helium flash?
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The core quickly heats up and expands.
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What is a carbon star?
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a red giant star whose atmosphere becomes carbon-rich through convection from the core
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What is a planetary nebula?
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the expanding shell of gas that was ejected in the final stages of a low-mass star's life that is no longer gravitationally bound to the remnant.
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In the end, the remaining core of a 1 solar mass star will be left behind as
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a white dwarf made primarily of carbon and oxygen.
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Right after it forms, a white dwarf is (compared to the star it evolved from)
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hotter and dimmer.
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Most interstellar dust grains are produced in
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the atmospheres of red giant stars.
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What can we learn about a star from a life track on an H-R diagram?
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what surface temperature and luminosity it will have at each stage of its life
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Which of the following types of data provide evidence that helps us understand the life tracks of low-mass stars?
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H-R diagrams of globular clusters
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How are low-mass red giant stars important to our existence?
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These stars manufactured most of the carbon and oxygen atoms in the universe.
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What is the CNO cycle
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a type of hydrogen fusion that uses carbon, nitrogen, and oxygen atoms as catalysts
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In order to predict whether a star will eventually fuse carbon, what do you need to know about the star?
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its mass
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High mass stars evolve more rapidly than low mass ones because the high mass stars
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have higher core temperatures.
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Carbon fusion occur in high-mass stars but not in low-mass stars because
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the cores of low-mass stars never get hot enough for carbon fusion.
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Which of the following statements about various stages of core nuclear burning (hydrogen, helium, carbon, etc.) in a high-mass star is not true?
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Each successive stage lasts for approximately the same amount of time.
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The temperature of a star's core will
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increase as the star fuses heavier and heavier elements.
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Observations show that elements with even numbers of protons (such as oxygen, neon, and magnesium) tend to be more abundant in the universe than elements with atomic mass numbers in between. Why do we think this is the case?
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At the end of a high-mass star's life, it produces new elements through a series of helium capture reactions.
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Which element has the lowest mass per nuclear particle and therefore cannot release energy by either fusion or fission?
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iron
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Suppose that hydrogen, rather than iron, had the lowest mass per nuclear particle. Which of the following would be true?
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Nuclear fusion could not power stars.
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What types of stars end their lives with supernovae?
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stars that are at least several times the mass of the Sun
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Why is iron significant to understanding how a supernova occurs?
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Iron cannot release energy either by fission or fusion.
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Which event marks the beginning of a supernova?
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the sudden collapse of an iron core into a compact ball of neutrons
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After a supernova event, what is left behind?
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either a neutron star or a black hole
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Suppose the star Betelgeuse (in Orion) were to become a supernova tomorrow (as seen here on Earth). What would it look like to the naked eye?
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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.
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Why is Supernova 1987A particularly important to astronomers?
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It is the nearest supernova to have occurred at a time when we were capable of studying it carefully with modern telescopes.
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Where does gold (the element) come from?
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It is produced during the supernova explosions of high-mass stars.
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Why do scientists think that our solar system must have formed sometime after nearby supernovae explosions?
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Existence of heavy elements
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What happens when the gravity of a massive star is able to overcome neutron degeneracy pressure?
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The core contracts and becomes a black hole.
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Which is more common: a star blows up as a supernova, or a star forms a planetary nebula/white dwarf system?
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Planetary nebula formation is more common.
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A spinning neutron star has been observed at the center of a
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supernova remnant.
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You discover a binary star system in which one member is a 15MSun main-sequence star and the other star is a 10MSun giant. Why should you be surprised, at least at first?
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The two stars should be the same age, so the more massive one should have become a giant first.
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You discover a binary star system in which one member is a15MSun main-sequence star and the other star is a 10MSun giant. How do we believe that a star system such as this might have come to exist?
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The giant must once have been the more massive star but transferred some of its mass to its companion.
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