ASTR 101: TEST 2
49 Cards in this Set
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What is the purpose of interferometry?
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It allows two or more small telescopes to achieve the angular resolution of a much larger telescope.
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The spectra of most galaxies show redshifts. This means that their spectral lines _________.
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have wavelengths that are longer than normal
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Suppose you want to know the chemical composition of a distant star. Which piece of information is most useful to you?
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the wavelengths of spectral lines in the star's spectrum
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According to our present theory of solar system formation, which of the following lists the major ingredients of the solar nebula in order from the most abundant to the least abundant?
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hydrogen and helium gas; hydrogen compounds; rock; metal
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According to modern science, approximately how old is the Sun?
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4 1/2 billion years
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The Sun will exhaust its nuclear fuel in about ______.
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5 billion years
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The source of energy that keeps the Sun shining today is _________.
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nuclear fusion
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What is the solar wind?
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a stream of charged particles flowing outward from the surface of the Sun
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The proton-proton chain is _________.
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the specific set of nuclear reactions through which the Sun fuses hydrogen into helium
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What happens to energy in the Sun's convection zone?
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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?
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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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Which of the following statements about X rays and radio waves is not true?
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X rays travel through space faster than radio waves.
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Suppose you built a scale-model atom in which the nucleus is the size of a tennis ball. About how far would the cloud of electrons extend?
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Several kilometers
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Isotopes are a difference in what?
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Neutrons
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Which of the following statements about thermal radiation is always true?
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A hot object emits more radiation per unit surface area than a cool object.
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Betelgeuse is the bright red star representing the left shoulder of the constellation Orion. All the following statements about Betelgeuse are true. Which one can you infer from its red color?
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Its surface is cooler than the surface of the Sun.
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Laboratory measurements show hydrogen produces a spectral line at a wavelength of 486.1 nanometers (nm). A particular star's spectrum shows the same hydrogen line at a wavelength of 486.0 nm. What can we conclude?
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The star is moving toward us.
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How does the light-collecting area of an 8-meter telescope compare to that of a 2-meter telescope?
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The 8-meter telescope is 4 times larger in diameter, so its light collecting area is 42 = 16 times greater. (16 x greater than 2-meter)
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The Chandra X-ray Observatory must operate in space because:
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X rays do not penetrate Earth's atmosphere.
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Which of the following is always true about images captured with X-ray telescopes?
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They are always shown with colors that are not the true colors of the objects that were photographed.
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How is Einstein's famous equation, E=mc2, important in understanding the Sun?
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the Sun generates energy to shine by losing 4 million tons of mass each second
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The following statements are all true. Which one counts as an "exception to the rule" in being unusual for our solar system?
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The diameter of Earth's Moon is about 1/4 that of Earth.
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About 2% of our solar nebula consisted of elements besides hydrogen and helium. However, the very first generation of star systems in the universe probably consisted only of hydrogen and helium. Which of the following statements is most likely to have been true about these first-generatio…
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There were no comets or asteroids in these first-generation star systems.
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According to our present theory of solar system formation, which of the following best explains why the solar nebula ended up with a disk shape as it collapsed?
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It flattened as a natural consequence of collisions between particles in the nebula.
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What is the primary basis upon which we divide the ingredients of the solar nebula into four categories (hydrogen/helium; hydrogen compound; rock; metal)?
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The temperatures at which various materials will condense from gaseous form to solid form.
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According to our present theory of solar system formation, which of the following statements about the growth of terrestrial and jovian planets is not true?
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The jovian planets began from planetesimals made only of ice, while the terrestrial planets began from planetesimals made only of rock and metal.
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According to present understanding, which of the following statements about the solar wind is not true?
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It is even stronger today than it was when the Sun was young.
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According to our present theory of solar system formation, how did Earth end up with enough water to make oceans?
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The water was brought to the forming Earth by planetesimals that accreted beyond the orbit of Mars.
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According to our basic scenario of solar system formation, why do the jovian planets have numerous large moons?
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As the growing jovian planets captured gas from the solar nebula, the gas formed swirling disks around them, and moons formed from condensation accretion within these disks.
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Which of the following is not evidence supporting the idea that our Moon formed as a result of a giant impact?
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The Pacific Ocean appears to be a large crater - probably the one made by the giant impact.
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Why are terrestrial planets denser than jovian planets?
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Only dense materials could condense in the inner solar nebula.
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How do scientists determine the age of the solar system?
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Radiometric dating of meteorites
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Which new idea has been added into our theory of solar system formation as a result of the discoveries of extrasolar planets?
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Planets can migrate from the orbits in which they are born.
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In the late 1800s, Kelvin and Helmholtz suggested that the Sun stayed hot due to gravitational contraction. What was the major drawback to this idea?
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It predicted that the Sun could shine for about 25 million years, but geologists had already found that Earth is much older than this.
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When is/was gravitational contraction an important energy generation mechanism for the Sun?
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It was important when the Sun was forming from a shrinking interstellar cloud of gas.
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Which of the following is the best answer to the question, "Why does the Sun shine?"
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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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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 _________.
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converted to an amount of energy equal to 4 million tons times the speed of light squared
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Which of the following best explains why nuclear fusion requires bringing nuclei extremely close together?
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Nuclei normally repel because they are all positively charged and can be made to stick only when brought close enough for the strong force to take hold.
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If the Sun's core suddenly shrank a little bit, what would happen in the Sun?
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The core would heat up, fusion rates would increase, the core would re-expand.
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The star Alpha Centauri A is the same type of star as the Sun, but its luminosity is about 1.6 times that of the Sun. What can we conclude?
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Alpha Centauri A fuses hydrogen into helium in its core at a higher rate than our Sun.
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How can we measure the strength of magnetic fields on the Sun?
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By looking for the splitting of spectral lines in the Sun's spectrum
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According to our theory of solar system formation, what three major changes occurred in the solar nebula as it shrank in size?
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It got hotter, its rate of rotation increased, and it flattened into a disk.
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Which of the following correctly describes how the process of gravitational contraction can make a star hot?
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When a star contracts in size, gravitational potential energy is converted to thermal energy.
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What do sunspots, solar prominences, and solar flares all have in common?
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They are all strongly influenced by magnetic fields on the Sun.
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According to our present theory of solar system formation, why were solid planetesimals able to grow larger in the outer solar system than in the inner solar system?
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Because only metal and rock could condense in the inner solar system, while ice also condensed in the outer solar system.
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The region of our solar system between Mercury and Mars has very few asteroids, while the region between Mars and Jupiter has many asteroids. Based on what you have learned, what is the most likely explanation for the lack of asteroids between Mercury and Mars?
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There were very few planetary leftovers in this region, because most of the solid material was accreted by the terrestrial planets as the planets formed.
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Based on everything you have learned about the formation of our solar system, which of the following statements is probably not true?
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Only a tiny percentage of stars are surrounded by spinning disks of gas during their formation.
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Many meteorites appear to have formed very early in the solar system's history. How do these meteorites support our theory about how the terrestrial planets formed?
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The meteorites appearance and composition is just what we'd expect if metal and rock condensed and accreted as our theory suggests.
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Why does the Sun emit neutrinos?
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Fusion in the Sun's core creates neutrinos.
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Study Guide ASTR 101