Astronomy Exam 3 – Flashcards
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How does the Sun's mass compare with that of the planets?
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It is a thousand times more massive than all the planets combined.
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Which planet has a ring system? Jupiter Saturn Uranus Neptune All of the above
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all of the above
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Which planet could an astronaut visit without the need for a spacesuit (and survive)? Mercury Venus the Moon Mars None; an astronaut would need a spacesuit to survive a visit to any other planet in the solar system.
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None; an astronaut would need a spacesuit to survive a visit to any other planet in the solar system.
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What are the main constituents of the jovian planets?
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hydrogen and helium
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Some astronomers suggest that, rather than being a planet, Pluto is really just a large member of
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Kuiper belt
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Why did the solar nebula heat up as it collapsed?
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As the cloud shrank, its gravitational potential energy was converted to thermal energy.
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What percentage of the solar nebula's mass consisted of hydrogen and helium gases?
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98%
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Approximately how many other planetary systems have been discovered to date?
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100
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How many of the planets orbit the Sun in the same direction as Earth does?
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all
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Planetary orbits in our solar system are:
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fairly circular and in the same plane.
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The composition of the solar nebula was 98%
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hydrogen and helium
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Are there any exceptions to the rule that planets rotate with small axis tilts and in the same direction as they orbit the Sun?
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Venus and Uranus are exceptions.
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Leftover ice-rich planetesimals are called
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comets.
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What's unusual about our Moon?
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It's surprisingly large relative to the planet it orbits.
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About how old is the solar system?
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4.5 billion years
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On average, Venus has the hottest surface temperature of any planet in the solar system.
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true
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Our Moon is about the same size as moons of the other terrestrial planets.
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false
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The weather conditions on Mars today are much different than they were in the distant past.
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true
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Moons cannot have atmospheres, active volcanoes, or liquid water.
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false
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Saturn is the only planet in the solar system with rings.
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false
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Neptune orbits the Sun in the opposite direction of all the other planets.
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false
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If Pluto were as large as the planet Mercury, we would classify it as a terrestrial planet.
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false
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Asteroids are made of essentially the same materials as the terrestrial planets.
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true
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When scientists say that our solar system is about 4 billion years old, they are making a rough estimate based on guesswork about how long it should have taken planets to form.
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false
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Is carbon-14 useful for establishing Earth's age? Why or why not?
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Carbon-14 is not useful for establishing the age of Earth because its half-life is too short in comparison to Earths age
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Rank the five terrestrial worlds in order of size from smallest to largest:
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Moon, Mercury, Mars, Venus, Earth.
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Spacecraft have landed on all the terrestrial worlds except:
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mercury
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Which of the following worlds has the most substantial atmosphere?
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venus
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What do we mean by a runaway greenhouse effect?
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a greenhouse effect that keeps getting stronger until all of a planet's greenhouse gases are in its atmosphere
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What is the importance of the carbon dioxide (CO2) cycle?
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It regulates the carbon dioxide concentration of our atmosphere, keeping temperatures moderate.
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Suppose we use a baseball to represent Earth. On this scale, the other terrestrial worlds (Mercury, Venus, the Moon, and Mars) would range in size approximately from that of _________.
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a golf ball to a baseball
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The two most important processes in heating the interiors of the terrestrial worlds are __________.
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(1) heat deposited by the process of formation; (2) heat released by radioactive decay
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The processes responsible for virtually all surface geology are _________.
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impact cratering, volcanisms, tectonics, and erosion
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Which of the following is the most basic definition of a greenhouse gas?
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a gas that absorbs infrared light
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Suppose we represent Earth with a basketball. On this scale, most of the air in Earth's atmosphere would fit in a layer that is _________.
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about the thickness of a sheet of paper
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Which of the following does NOT provide evidence that Mars once had abundant liquid water on its surface?
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the presence of canali, discovered in the late 1800s by Giovanni Schiaparelli and mapped by Percival Lowell
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Earth has been gradually warming over the past few decades. Based on a great deal of evidence, scientists believe that this warming is caused by _____.
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human activities that are increasing the concentration of greenhouse gases in Earth's atmosphere
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Which heat source continues to contribute to Earth's internal heat?
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radioactive decay
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In general, what kind of terrestrial planet would you expect to have the thickest lithosphere?
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a small planet
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What do we conclude if a planet has few impact craters of any size?
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Other geological processes have wiped out craters.
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How many of the five terrestrial worlds are considered "geologically dead"?
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two
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skip
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water vapor
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Which describes our understanding of flowing water on Mars?
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It was important once, but no longer.
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Which terrestrial world has the most atmospheric gas?
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venus
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What, if anything, do you think we should be doing to alleviate the threat of global warming?
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improve energy efficiency reduce the emissions of greenhouse gases replace fossil fuels with alternative energy sources
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Which of the following is a general characteristic of the four jovian planets in our solar system?
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They are lower in average density than are the terrestrial planets
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Which of the following best describes the internal layering of Jupiter, from the center outward?
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core of rock, metal, and hydrogen compounds; thick layer of metallic hydrogen; layer of liquid hydrogen; layer of gaseous hydrogen; cloud layer
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How do typical wind speeds in Jupiter's atmosphere compare to typical wind speeds on Earth?
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They are much faster than hurricane winds on Earth.
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What atmospheric constituent is responsible for the blue color of Uranus and Neptune?
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methane
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Which of the following statements about the moons of the jovian planets is NOT true? Most of the moons are large enough to be spherical in shape, but a few have the more potato-like shapes of asteroids. Many of the moons are made largely of ices. Some of the moons are big enough that we'd call them planets (or dwarf planets) if they orbited the Sun. One of the moons has a thick atmosphere.
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Most of the moons are large enough to be spherical in shape, but a few have the more potato-like shapes of asteroids.
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Which statement about Io is true?
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It is the most volcanically active body in our solar system.
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Which moon has a thick atmosphere made mostly of nitrogen?
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Titan
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Suppose you could float in space just a few meters above Saturn's rings. What would you see as you looked down on the rings?
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countless icy particles, ranging in size from dust grains to large boulders
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Which moon is considered likely to have a deep, subsurface ocean of liquid water?
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europa
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A rock found on Earth that crashed down from space is called _________.
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meteorite
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The asteroid belt is located _________.
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between the orbits of mars and jupiter
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Which of the following statements about asteroids, Kuiper belt objects, and Oort cloud objects is true?
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Objects in the asteroid belt and Kuiper belt orbit the Sun in nearly the same plane as the planets, but objects in the Oort cloud do not.
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Which direction do a comet's dust and plasma tails point?
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generally away from the sun
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According to current evidence, Pluto is best explained as ______.
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a large member of the Kuiper belt
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Which moon shows evidence of rainfall and erosion by some liquid substance?
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titan
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Io experiences tidal heating primarily because __________.
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Io's elliptical orbit causes the tidal force on Io to vary as it orbits Jupiter
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From Part A, Io's elliptical orbit is necessary to its tidal heating. This elliptical orbit, in turn, is a result of the orbital resonance among Io, Europa, and Ganymede. This orbital resonance causes Io to have a more elliptical orbit than it would otherwise, because __________.
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Io periodically passes Europa and Ganymede in the same orbital position
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We cannot see tidal forces or tidal heating; rather, we predict that they must occur based on the orbital characteristics of the moons. What observational evidence confirms that tidal heating is important on Io?
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active volcanoes on Io
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The orbital resonance also gives Europa an elliptical orbit, so it also experiences tidal heating. However, Europa experiences less tidal heating than Io, because Europa __________ than Io.
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is farther from jupiter
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We now know of many Jupiter-size planets around other stars. Suppose that future observations show that one of these planets has two orbiting moons. What additional information, if any, would we need to decide whether these moons experience tidal heating?
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we need to know their orbital periods
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Saturn's rings are composed of __________.
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lots of individual particles of ice and rock
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Saturn's rings look bright because __________.
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light from the Sun reflects off the material in the rings
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Which of the following statements correctly describes the motion of the particles in Saturn's rings?
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Particles in the inner rings orbit Saturn at a faster speed than particles in the outer rings.
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The main ingredients of most satellites of the jovian planets are
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hydrogen compound ices.
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Some jovian planets give off more energy than they receive because of
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ongoing contraction or differentiation.
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Why does Neptune appear blue and Jupiter red?
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Methane in Neptune's atmosphere absorbs red light.
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The asteroid belt lies between the orbits of
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mars and jupiter
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Did a large terrestrial planet ever form in the region of the asteroid belt?
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No, because Jupiter prevented one from accreting
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How big an object causes a typical shooting star?
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a grain of sand or a small pebble
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Which are thought to have formed farthest from the Sun?
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Kuiper belt comets
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A comet entering the inner solar system from afar will __________.
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form a coma and some time later form a tail
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During the time that a comet passes through the inner solar system, the comet can appear quite bright because __________.
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sunlight reflects off the comet's tail and coma
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A comet's plasma tail always points directly away from the Sun because __________.
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of pressure exerted by the fast-moving charged particles in the solar wind
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What does Pluto most resemble?
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a comet
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From the viewpoint of an alien astronomer, how does Jupiter affect observations of our Sun?
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It causes the Sun to move in a small ellipse with an orbital period of about 12 years.
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Suppose you are using the Doppler method to look for planets around another star. What must you do?
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Compare many spectra of the star taken over a period of many months or years.
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In general, which type of planet would you expect to cause the largest Doppler shift in the spectrum of its star?
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a massive planet that is close to its star
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Suppose a planet is discovered by the Doppler method and is then discovered to have transits. In that case, we can determine all the following about the planet except __________.
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its rotation period
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The transit method allows us in principle to find planets around __________.
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only a small fraction of stars that have planets
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You observe a star very similar to our own Sun in size and mass. This star moves very slightly back and forth in the sky once every 4 months, and you attribute this motion to the effect of an orbiting planet. What can you conclude about the orbiting planet?
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The planet must be closer to the star than Earth is to the Sun.
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Which of the following will allow you to learn something about a transiting planet's atmospheric composition?
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Compare spectra obtained before and during an eclipse.
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Very few of the known extrasolar planets have sizes as small as Earth. The most likely reason for this fact is that __________.
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small planets are more difficult to detect than larger planets
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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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To date, we've found very few planets orbiting their stars at distances comparable to the distances of the jovian planets in our solar system. Why do astronomers think this is the case?
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We have not yet been searching for planets at such distances for a long enough time.
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Current evidence suggests that some massive jovian planets orbit at very close orbital distances to their stars. How do we think these planets ended up on these close orbits?
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These planets migrated inward after being born on orbits much farther from their stars.
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Assuming that our ideas about how "hot Jupiters" ended up on their current orbits are correct, why didn't our own solar system end up with any hot Jupiters?
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Our solar nebula must have been blown into space shortly after the formation of the jovian planets.
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When is the soonest we are likely to have moderate-resolution images and spectra of Earthlike planets around other stars?
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In a decade or two, through space observatories now in the early planning stages.
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What is an extrasolar planet?
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A planet that orbits a star that is not our own Sun
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The first confirmed detections of extrasolar planets occurred in ____________.
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the 1990's
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What do the astrometric, Doppler, and transit methods share in common?
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They all search for planets by measuring properties of a star rather than of the planets themselves.
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The astrometric method looks for planets with careful measurements of a star's _________.
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position in the sky
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In essence, the Kepler mission searched for extrasolar planets by ____________.
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monitoring stars for slight dimming that might occur as unseen planets pass in front of them
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Can we determine orbital distances for extrasolar planets using the astrometric, Doppler, or transit methods?
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Yes: All three methods give us direct information about a planet's orbital period, from which we can use Newton's version of Kepler's third law to calculate the planet's distance.
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Why do we say that the Doppler method gives a planet's "minimum mass"?
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The size of the Doppler shift that we detect depends on the tilt of a planet's orbit.
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Which of the following statements is not true about the planets so far discovered around other stars?
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Photographs reveal that most of them have atmospheres much like that of Jupiter.
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What do we mean by a "hot Jupiter"?
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a planet that is Jupiter-like in size but orbits very close to its star
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Overall, what do current data suggest about planetary types in other planetary systems?
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Planets come in a wider range of types than the planets in our solar system.
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Based on current data, about what fraction of stars have one or more planets?
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at least about 70%
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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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Jovian planets can migrate from the orbits in which they are born.
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Which of the following might explain the lack of "water worlds"—small planets made mostly of water or other hydrogen compounds—in our own solar system?
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In our solar system, the solar wind did not clear out gas until relatively late.
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How is the GAIA mission relevant to the search for extrasolar planets?
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It can detect planets through the astrometric method.
