AST 105 Exam 2 Ch 13

25 July 2022
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10^LSun
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What will the Sun's approximate luminosity be during the subgiant stage? https://session.masteringastronomy.com/problemAsset/2539469/2/Bennett_ch13.jpg
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3500 K
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When the Sun is a red giant, what will its approximate surface temperature be? https://session.masteringastronomy.com/problemAsset/2539469/2/Bennett_ch13.jpg
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10^4^LSun
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Just before the Sun produces a planetary nebula, what will its approximate luminosity be? https://session.masteringastronomy.com/problemAsset/2539469/2/Bennett_ch13.jpg
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10^βˆ’4^LSun
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When the Sun becomes a white dwarf with a surface temperature similar to its current surface temperature, what will its luminosity be? https://session.masteringastronomy.com/problemAsset/2539469/2/Bennett_ch13.jpg
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shrink and heat
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When the core of a star like the Sun uses up its supply of hydrogen for fusion, the core begins to ________.
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Degeneracy pressure and Fusion of another element.
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When a star exhausts its core fusion fuel so that the core begins to contract, which of the following can stop the contraction?
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It has the lowest mass per nuclear particle.
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In what way is iron unique among the elements?
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supernova
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When it dies, a high-mass star explodes as a _______________.
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inert helium core
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A star that is expanding (into a subgiant and then a giant) has a(n) ________________________.
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high-mass stars
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Stars with mass greater than about 8 solar masses are considered _____________.
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hydrogen shell fusion
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The energy that drives the expansion of a star into a subgiant or red giant comes from ___________________________.
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helium fusion
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The final stage of core fusion in a low-mass star is ___________________.
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low-mass stars
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Stars with masses less than about two solar masses are considered ______________.
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planetary nebula
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When it dies, a low-mass star expels a _________________________.
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main-sequence stars
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Stars that are fusing hydrogen in their cores are _______________________.
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Nuclear fusion and gravitational contraction
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Which two processes can generate energy to help a star maintain its internal thermal pressure?
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low-mass star
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Our Sun is considered to be a _________.
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The cloud must radiate much of its thermal energy.
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Which process is required to allow a gravitationally collapsing gas cloud to continue to collapse?
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The onset of core hydrogen fusion
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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?
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hotter and dimmer
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Generally speaking, a main-sequence star is __________ than it was during the time it was a protostar.
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A few massive stars will form, live, and die before the majority of the star's clusters even complete their protostar stage.
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Consider a large molecular cloud that will give birth to a cluster of stars. Which of the following would you expect to be true?
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Brown dwarfs would outnumber all ordinary stars.
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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?
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Below and to the right of the lowest part of the main sequence
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Where would a brown dwarf be located on an H-R diagram?
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H-R diagrams of globular clusters
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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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stage 2
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This diagram represents the life track of a 1 solar mass star from its pre-main-sequence stages to just before its final death. Refer to the life stages labeled with roman numerals. The figure schematically shows an HR-diagram with the main sequence of stars. Spectral classes O, B, A, F, G, K, and M are labeled along the x-axis from left to right. Luminosity divided by the Sun's luminosity is measured on the y-axis. The life track of a star contains eight labeled stages. The first stage is the starting point and lays in the region beyond the main sequence area. At the second stage, luminosity decreases and the spectral class changes from M to G. The star reaches the main sequence, where it remains for the third stage. At the fourth stage luminosity increases and the spectral class changes back to M. At this configuration, the star goes through the fifth stage. At the sixth stage, luminosity slightly decreases and the spectral class changes to G, again, not reaching the main sequence. At this configuration, the star goes through the seventh stage. At the eighth stage, luminosity increases while spectral class G is contained. During which stage is the star's energy supplied by primarily by gravitational contraction? https://session.masteringastronomy.com/problemAsset/2639961/5/ch12_Q_8_12.jpg
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stage 4
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This diagram represents the life track of a 1 solar mass star from its pre-main-sequence stages to just before its final death. Refer to the life stages labeled with roman numerals. The figure schematically shows an HR-diagram with the main sequence of stars. Spectral classes O, B, A, F, G, K, and M are labeled along the x-axis from left to right. Luminosity divided by the Sun's luminosity is measured on the y-axis. The life track of a star contains eight labeled stages. The first stage is the starting point and lays in the region beyond the main sequence area. At the second stage, luminosity decreases and the spectral class changes from M to G. The star reaches the main sequence, where it remains for the third stage. At the fourth stage luminosity increases and the spectral class changes back to M. At this configuration, the star goes through the fifth stage. At the sixth stage, luminosity slightly decreases and the spectral class changes to G, again, not reaching the main sequence. At this configuration, the star goes through the seventh stage. At the eighth stage, luminosity increases while spectral class G is contained. During which stage does the star have an inert (non-burning) helium core? https://session.masteringastronomy.com/problemAsset/2639961/5/ch12_Q_8_12.jpg
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stage 3
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This diagram represents the life track of a 1 solar mass star from its pre-main-sequence stages to just before its final death. Refer to the life stages labeled with roman numerals. The figure schematically shows an HR-diagram with the main sequence of stars. Spectral classes O, B, A, F, G, K, and M are labeled along the x-axis from left to right. Luminosity divided by the Sun's luminosity is measured on the y-axis. The life track of a star contains eight labeled stages. The first stage is the starting point and lays in the region beyond the main sequence area. At the second stage, luminosity decreases and the spectral class changes from M to G. The star reaches the main sequence, where it remains for the third stage. At the fourth stage luminosity increases and the spectral class changes back to M. At this configuration, the star goes through the fifth stage. At the sixth stage, luminosity slightly decreases and the spectral class changes to G, again, not reaching the main sequence. At this configuration, the star goes through the seventh stage. At the eighth stage, luminosity increases while spectral class G is contained. Which stage lasts the longest? https://session.masteringastronomy.com/problemAsset/2639961/5/ch12_Q_8_12.jpg
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stage 8
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This diagram represents the life track of a 1 solar mass star from its pre-main-sequence stages to just before its final death. Refer to the life stages labeled with roman numerals. The figure schematically shows an HR-diagram with the main sequence of stars. Spectral classes O, B, A, F, G, K, and M are labeled along the x-axis from left to right. Luminosity divided by the Sun's luminosity is measured on the y-axis. The life track of a star contains eight labeled stages. The first stage is the starting point and lays in the region beyond the main sequence area. At the second stage, luminosity decreases and the spectral class changes from M to G. The star reaches the main sequence, where it remains for the third stage. At the fourth stage luminosity increases and the spectral class changes back to M. At this configuration, the star goes through the fifth stage. At the sixth stage, luminosity slightly decreases and the spectral class changes to G, again, not reaching the main sequence. At this configuration, the star goes through the seventh stage. At the eighth stage, luminosity increases while spectral class G is contained. During which stage does the star have an inert (non-burning) carbon core surrounded by shells of helium and hydrogen burning? https://session.masteringastronomy.com/problemAsset/2639961/5/ch12_Q_8_12.jpg
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Its outer layers will be ejected as a planetary nebula and its core will become a white dwarf.
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This diagram represents the life track of a 1 solar mass star from its pre-main-sequence stages to just before its final death. Refer to the life stages labeled with roman numerals. The figure schematically shows an HR-diagram with the main sequence of stars. Spectral classes O, B, A, F, G, K, and M are labeled along the x-axis from left to right. Luminosity divided by the Sun's luminosity is measured on the y-axis. The life track of a star contains eight labeled stages. The first stage is the starting point and lays in the region beyond the main sequence area. At the second stage, luminosity decreases and the spectral class changes from M to G. The star reaches the main sequence, where it remains for the third stage. At the fourth stage luminosity increases and the spectral class changes back to M. At this configuration, the star goes through the fifth stage. At the sixth stage, luminosity slightly decreases and the spectral class changes to G, again, not reaching the main sequence. At this configuration, the star goes through the seventh stage. At the eighth stage, luminosity increases while spectral class G is contained. What will happen to the star after stage viii? https://session.masteringastronomy.com/problemAsset/2639961/5/ch12_Q_8_12.jpg
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Fusion reactions are producing energy at a greater rate in the red giant.
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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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the cores of low-mass stars never get hot enough for carbon fusion
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Carbon fusion occur in high-mass stars but not in low-mass stars because _________.
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Each successive stage lasts for approximately the same amount of time.
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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?
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The sudden collapse of an iron core into a compact ball of neutrons
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Which event marks the beginning of a supernova?
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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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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?
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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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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?
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supernova remnant
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A spinning neutron star has been observed at the center of a _________.
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Planetary nebula formation is more common.
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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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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
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You discover a binary star system in which one star is a 15 M Sun main-sequence star and the other is a 10 M Sun giant. How do we think that a star system such as this might have come to exist?
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the cool clouds in which stars form
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The interstellar clouds called molecular clouds are _________.
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A star that is still in the process of forming
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What is a protostar?
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thermal pressure
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Most interstellar clouds remain stable in size because the force of gravity is opposed by _______ within the cloud.
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infrared
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Which part of the electromagnetic spectrum generally gives us our best views of stars forming in dusty clouds?
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A cold, dense gas cloud
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What kind of gas cloud is most likely to give birth to stars?
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Intense ultraviolet radiation coming from a protostar
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Which of the following phenomena is not commonly associated with the star-formation process?
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When the rate of hydrogen fusion becomes high enough to balance the rate at which the star radiates energy into space
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When does a protostar become a main-sequence star?
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10 million K
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Approximately what core temperature is required before hydrogen fusion can begin in a star?
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A 1 solar mass star
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Which star spends the longest time in the protostellar phase of life?
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0.1 to 150 solar masses
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What is the approximate range of masses that newborn main-sequence stars can have?
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less massive than the Sun
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The vast majority of stars in a newly formed star cluster are _________.
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Brown dwarfs eventually collapse to become white dwarfs.
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Which of the following statements about brown dwarfs is not true?
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The surface temperature and luminosity the star will have at each stage of its life
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What can we learn about a star from a life track on an H-R diagram?
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The pillars are clouds of gas and dust in which many new stars are forming; the edges of the pillars are sculpted by ultraviolet radiation from stars outside the pillars.
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This famous image from the Hubble Space Telescope shows what is sometimes called the "pillars of creation." Which of the following best describes what it shows? https://session.masteringastronomy.com/problemAsset/2640049/4/VQ_13.png
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It is flowing outward in two opposite directions from the protostar.
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This photo shows gas associated with a protostar. What is this gas doing? https://session.masteringastronomy.com/problemAsset/2640049/4/16_15_Figure.jpg
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Low-mass stars are much more common than higher-mass stars.
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What is the main idea captured by this graph? https://session.masteringastronomy.com/problemAsset/2640049/4/16_10_VQ.jpg
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Fusion of helium into carbon
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In this diagram, red balls represent protons and gray balls represent neutrons. What reaction is being shown? https://session.masteringastronomy.com/problemAsset/2640049/4/17_01_VQ.jpg
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Point 4
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This H-R diagram shows the life track of a 1 M Sun star from the time it first becomes a main-sequence star. Which numbered point represents the star when it has both hydrogen-fusing and helium-fusing shells around an inert carbon core? https://session.masteringastronomy.com/problemAsset/2640049/4/17_03_VQ.jpg
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A white dwarf
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This Hubble Space Telescope photo shows a planetary nebula. What is the white dot in the center (indicated by the arrow)? https://session.masteringastronomy.com/problemAsset/2640049/4/12-04-vq.jpg
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greater than 8 times the mass of the Sun
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Suppose a particular star has a core that is undergoing multiple stages of fusion simultaneously to give it the structure shown in this diagram. Based on your understanding of stellar lives, the mass of this star is __________. https://session.masteringastronomy.com/problemAsset/2640049/4/17_12_Figure.jpg
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Hydrogen is about 10,000 times as abundant as nitrogen.
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According to this diagram, how much more abundant is hydrogen in the universe than nitrogen? https://session.masteringastronomy.com/problemAsset/2640049/4/12_07_VQ.jpg
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An expanding cloud of remains from a star that died in a supernova.
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This photo shows the famous Crab Nebula. What is it? https://session.masteringastronomy.com/problemAsset/2640049/4/12_08_VQ.jpg
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It was a high-mass star with at least 8 times the mass of the Sun.
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The arrow in the photo on the left points to the star that we see as a supernova in the photo on the right. What can we conclude about this star? https://session.masteringastronomy.com/problemAsset/2640049/4/17_18_Figure.jpg
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protostar, main-sequence star, red giant, planetary nebula, white dwarf
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Which of the following lists the stages of life for a low-mass star in the correct order?
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The core shrinks while the rest of the star expands.
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What happens when a main-sequence star exhausts its core hydrogen fuel supply?
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hydrogen fusion in a shell surrounding the central 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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three helium nuclei fuse to form one carbon nucleus
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The overall helium fusion reaction is __________.
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The sudden onset of helium fusion in the core of a low-mass star
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What is a helium flash?
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Gas ejected from a low-mass star in the final stage of its life
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What is a planetary nebula?
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become a white dwarf that will slowly cool with time
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The ultimate fate of our Sun is to _________.
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A set of steps by which four hydrogen nuclei fuse into one helium nucleus
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What is the CNO cycle?
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its mass
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To predict whether a star will eventually fuse oxygen into a heavier element, you mainly want to know what fact about the star?
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Iron cannot release energy either by fission or fusion.
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Why is iron significant to understanding how a supernova occurs?
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may be either a neutron star or a black hole
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After a supernova explosion, the remains of the stellar core _________.
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It is the nearest supernova to have occurred at a time when we were capable of studying it carefully with telescopes.
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Why is Supernova 1987A particularly important to astronomers?
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The two stars should be the same age, so we'd expect the subgiant to be more massive than the main-sequence star.
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Algol consist of a 3.7 MSun main-sequence star and a 0.8 MSun subgiant. Why does this seem surprising, at least at first?