AST CH 14

25 July 2022
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question
the light radiated from the Sun's surface reaches Earth in about 8 minutes, but the energy of that light was released by fusion in the solar core about tens of thousands of years ago. hundreds of thousands of years ago. a million years ago. a hundred years ago. a thousand years ago.
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hundreds of thousands of years ago.
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Sunspots are cooler than the surrounding solar surface because they are regions where convection carries cooler material downward. magnetic fields lift material from the surface of the Sun, cooling off the material faster. magnetic fields trap ionized gases that absorb light. there is less fusion occurring there. strong magnetic fields slow convection and prevent hot plasma from entering the region.
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strong magnetic fields slow convection and prevent hot plasma from entering the region.
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Studies of sunquakes, or helioseismology, have revealed that neutrinos from the solar core reach the solar surface easily. "sunquakes" are caused by similar processes that create earthquakes on Earth. our mathematical models of the solar interior are fairly accurate. the Sun vibrates only on the surface. the Sun generates energy by nuclear fusion.
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our mathematical models of the solar interior are fairly accurate.
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What happens to energy in the Sun's convection zone? Energy is produced in the convection zone by nuclear fusion. Energy is transported outward by the rising of hot plasma and sinking of cooler plasma. Energy is produced in the convection zone by thermal radiation. Energy slowly leaks outward through the radiative diffusion of photons that repeatedly bounce off ions and electrons.
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Energy is transported outward by the rising of hot plasma and sinking of cooler plasma.
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How is the sunspot cycle directly relevant to us here on Earth? Coronal mass ejections and other activity associated with the sunspot cycle can disrupt radio communications and knock out sensitive electronic equipment. The sunspot cycle strongly influences Earth's weather. The Sun's magnetic field, which plays a major role in the sunspot cycle, affects compass needles that we use on Earth. The brightening and darkening of the Sun that occurs during the sunspot cycle affects plant photosynthesis here on Earth. The sunspot cycle is the cause of global warming.
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Coronal mass ejections and other activity associated with the sunspot cycle can disrupt radio communications and knock out sensitive electronic equipment.
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What is the Sun made of (by mass)? 90% dark matter, 10% ordinary matter 50% hydrogen, 25% helium, 25% other elements 100% hydrogen and helium 70% hydrogen, 28% helium, 2% other elements
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70% hydrogen, 28% helium, 2% other elements
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In the late 1800s, Kelvin and Helmholtz suggested that the Sun stayed hot thanks to gravitational contraction. What was the major drawback of this idea? It is physically impossible to generate heat simply by making a star shrink in size. It predicted that the Sun would shrink noticeably as we watched it, and the Sun appears to be stable in size. It predicted that Earth would also shrink, which would make it impossible to have stable geology on our planet. It predicted that the Sun could last only about 25 million years, which is far less than the age of Earth. It was proposed before Einstein's theory of general relativity and was therefore incorrect.
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It predicted that the Sun could last only about 25 million years, which is far less than the age of Earth.
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What is granulation in the Sun? the bubbling pattern on the photosphere produced by the underlying convection another name for the way sunspots look on the surface of the Sun elements in the Sun other than hydrogen and helium lumps of denser material in the Sun dust particles in the Sun that haven't been turned into plasma
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the bubbling pattern on the photosphere produced by the underlying convection
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Which layer of the Sun do we normally see? radiation zone chromosphere photosphere convection zone corona
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photosphere
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What are the appropriate units for the Sun's luminosity? Newtons watts joules kilograms
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watts
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The fundamental nuclear reaction occurring in the core of the Sun is radioactive decay. nuclear fission. nuclear fusion of hydrogen into helium. nuclear fusion of helium to carbon.
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nuclear fusion of hydrogen into helium.
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From center outward, which of the following lists the "layers" of the Sun in the correct order? core, radiation zone, convection zone, corona, chromosphere, photosphere core, radiation zone, convection zone, photosphere, chromosphere, corona core, corona, radiation zone, convection zone, photosphere, chromosphere core, convection zone, radiation zone, corona, chromosphere, photosphere
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core, radiation zone, convection zone, photosphere, chromosphere, corona
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When we say that the Sun is a ball of plasma, we mean that the Sun is made of material that acts like a liquid acts on Earth. the Sun is made of atoms and molecules. the Sun is roughly the same color as blood. the Sun consists of gas in which many or most of the atoms are ionized (missing electrons).
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the Sun consists of gas in which many or most of the atoms are ionized (missing electrons).
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Which of the following best explains why the Sun's luminosity gradually rises over billions of years? The Sun's core gradually expands with time, and this expansion means there is more room for energy to be generated and hence increases the Sun's luminosity. Fusion gradually decreases the number of independent particles in the core, allowing gravity to compress and heat the core, which in turn increases the fusion rate and the Sun's luminosity. The planets need more and more energy to maintain any life on them as time goes on, and therefore the Sun must bet hotter. Nuclear reactions in the Sun become more efficient with time, so that each fusion reaction releases more energy when the Sun is old than when it is young; this in turn raises the Sun's luminosity.
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Fusion gradually decreases the number of independent particles in the core, allowing gravity to compress and heat the core, which in turn increases the fusion rate and the Sun's luminosity.
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Why are neutrinos so difficult to detect? They are extremely rare. They have no mass. They have a tendency to pass through just about any material without any interactions.
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They have a tendency to pass through just about any material without any interactions.
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Which of the following is the best answer to the question, "Why does the Sun shine?" The Sun initially began making energy through chemical reactions. These heated the interior enough to allow gravitational contraction and nuclear fusion to occur. As the Sun was forming, gravitational contraction increased the Sun's temperature until the core become hot enough for nuclear fusion, which ever since has generated the heat that makes the Sun shine. The Sun initially began generating energy through nuclear fusion as it formed, but today it generates energy primarily through the sunspot cycle. As the Sun was forming, nuclear fusion reactions in the shrinking clouds of gas slowly became stronger and stronger, until the Sun reached its current luminosity.
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As the Sun was forming, gravitational contraction increased the Sun's temperature until the core become hot enough for nuclear fusion, which ever since has generated the heat that makes the Sun shine.
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What do we mean when we say that the Sun is in gravitational equilibrium? The Sun maintains a steady temperature. There is a balance within the Sun between the outward push of pressure and the inward pull of gravity. The hydrogen gas in the Sun is balanced so that it never rises upward or falls downward. The Sun always has the same amount of mass, creating the same gravitational force.
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There is a balance within the Sun between the outward push of pressure and the inward pull of gravity.
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Which of the following best describes the current status of our understanding of the solar neutrino problem? Experimental evidence indicates that the problem is solved and the expected number of solar neutrinos are indeed being produced by the Sun. We have learned that the Sun's interior undergoes fusion at a lower rate than we had expected, and that is why we had observed fewer neutrinos than expected. The solar neutrino problem remains as perplexing as ever, and indeed makes everything we think we know about stars suspect. The problem arose only because experimental data were being misinterpreted; on re-examination, the old data showed that the expected number of neutrinos were being detected.
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Experimental evidence indicates that the problem is solved and the expected number of solar neutrinos are indeed being produced by the Sun.
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What two forces are balanced in what we call gravitational equilibrium? outward pressure and the strong force outward pressure and inward gravity the electromagnetic force and gravity the strong force and kinetic energy the strong force and gravity
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outward pressure and inward gravity
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The phase of matter in the Sun is solid. gas. plasma. liquid.
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plasma.
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Which of the following correctly describes how the process of gravitational contraction can make a star hot? When a star contracts in size, gravitational potential energy is converted to thermal energy. Gravitational contraction involves nuclear fusion, which generates a lot of heat. Heat is generated when gravity contracts, because gravity is an inverse square law force. Gravitational contraction involves the generation of heat by chemical reactions, much like the burning of coal.
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When a star contracts in size, gravitational potential energy is converted to thermal energy.
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If the Sun's core suddenly shrank a little bit, what would happen in the Sun? The core would heat up, fusion rates would increase, and the core would re-expand. The density of the core would decrease, causing the core to cool off and expand. The core would cool off and continue to shrink as its density increased. The core would heat up, causing it to radiate so much energy that it would shrink even more.
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The core would heat up, fusion rates would increase, and the core would re-expand.
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The first step in the proton-proton chain produces an antielectron, or positron. What happens to the positron? It slowly works its way to the Sun's surface, where it escapes into space. It joins with a nearby neutron to form a proton. It is rapidly converted to energy when it meets an ordinary electron, resulting in matter-antimatter annihilation. It rapidly escapes from the Sun, traveling into space at nearly the speed of light. It quickly meets an ordinary electron, forming an electron-positron pair that remains stable.
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It is rapidly converted to energy when it meets an ordinary electron, resulting in matter-antimatter annihilation.
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Suppose you put two protons near each other. Because of the electromagnetic force, the two protons will join together to form a nucleus. repel each other. remain stationary. attract each other. collide.
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repel each other.
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What are coronal holes? tunnels in the outer layers of the Sun through which photons can escape more quickly than through the radiation zone regions on the photosphere where magnetic lines poke through, creating the cooler areas of the sunspots holes in the corona of the Sun that allow us to see the photosphere areas of the corona where magnetic field lines project into space, allowing charged particles to escape the Sun, becoming part of the solar wind
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areas of the corona where magnetic field lines project into space, allowing charged particles to escape the Sun, becoming part of the solar wind
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What is the average temperature of the surface of the Sun? 6,000 K 1 million K 1,000 K 100,000 K 10,000 K
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6,000 K
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Hydrogen fusion in the Sun requires a temperature (in Kelvin) of billions of degrees. trillions of degrees. thousands of degrees. millions of degrees.
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millions of degrees.
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What is the solution to the solar neutrino problem? Not all fusion reactions create electron neutrinos. The Sun is generating energy other than by nuclear fusion. The electron neutrinos created in the Sun change into another type of neutrino that we could not detect with our original equipment. The Sun is generating much less energy than we think it is. We do not know how to detect electron neutrinos.
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The electron neutrinos created in the Sun change into another type of neutrino that we could not detect with our original equipment.
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How does the Sun generate energy today? gravitational contraction gradually expanding in size nuclear fission chemical reactions nuclear fusion
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nuclear fusion
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Why does the Sun emit neutrinos? Convection releases neutrinos, which random walk through the radiation zone. The Sun was born with a supply of neutrinos that it gradually emits into space. Fusion in the Sun's core creates neutrinos. Solar flares create neutrinos with magnetic fields.
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Fusion in the Sun's core creates neutrinos.
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What is the solar wind? the wind that causes huge arcs of gas to rise above the Sun's surface a stream of charged particles flowing outward from the surface of the Sun the strong wind that blows sunspots around on the surface of the Sun the uppermost layer of the Sun, lying just above the corona
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a stream of charged particles flowing outward from the surface of the Sun
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Which statement best describes what was called the solar neutrino problem? Early experiments designed to detect solar neutrinos found them, but in fewer numbers than had been expected. Our understanding of fusion in the Sun suggested that neutrinos should be destroyed before they arrive at Earth, yet neutrinos were being detected. It referred to the fact that neutrinos are extremely difficult to detect. No one understood how it could be possible for neutrinos to be produced in the Sun.
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Early experiments designed to detect solar neutrinos found them, but in fewer numbers than had been expected.
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The proton-proton chain is an alternative way of generating energy that is different from the fusion of hydrogen into helium. the specific set of nuclear reactions through which the Sun fuses hydrogen into helium. another name for the force that holds protons together in atomic nuclei. the linkage of numerous protons into long chains.
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the specific set of nuclear reactions through which the Sun fuses hydrogen into helium.
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Which is closest to the temperature of the core of the Sun? 10 million K 100 million K 100,000 K 10,000 K 1 million K
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10 million K
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To estimate the central temperature of the Sun, scientists monitor changes in Earth's atmosphere. send probes to measure the temperature. use hot gas to create a small Sun in a laboratory. use computer models to predict interior conditions.
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use computer models to predict interior conditions.
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Based on its surface temperature of 5,800 K, what color are most of the photons that leave the Sun's surface? blue yellow red green orange
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green
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A computer accessory salesman attempts to convince you to purchase a "solar neutrino" shield for your new computer. (It's even "on sale"!) Why do you turn down this excellent offer? There's no such thing as a solar neutrino. Solar neutrinos are generated by solar winds, but we're in a solar minimum now, so the risk of damage is very low. Neutrinos rarely, if ever, interact with your computer. The Earth's natural magnetic field already offers excellent protection against the onslaught of solar neutrinos.
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Neutrinos rarely, if ever, interact with your computer.
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Every second, the Sun converts about 600 million tons of hydrogen into 596 million tons of helium. The remaining 4 million tons of mass is ejected into space in a solar wind. converted to an amount of energy equal to 4 million tons times the speed of light squared. reabsorbed as molecular hydrogen. ejected into space by solar flares.
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converted to an amount of energy equal to 4 million tons times the speed of light squared.