Chapter 9 – Astronomy – Flashcards
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What is the largest known asteroid in our solar system
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Ceres
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If all the material in the asteroid belt were to be combined to produce a planet, how big would it be?
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about 1500 km in diameter, less than half the diameter of the Moon
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An asteroid is
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a planetesimal moving in an orbit around the Sun.
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The asteroid belt exists between the orbits of the planets
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Mars and Jupiter.
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What is the average distance between asteroids?
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many times the distance between Earth and the Moon
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Where do the Trojan asteroids orbit the Sun?
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in circular orbits at the same orbital distance as Jupiter
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The major difference between the orbital paths of comets that we see in the inner solar system and those of the asteroids in the asteroid belt is that
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cometary orbits are highly elliptical and at random inclinations to the ecliptic plane compared with the circular orbits of asteroids in the ecliptic plane.
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The most likely origin of the "dirty snowballs" that become comets when they are deflected into orbits that bring them closer to the Sun is the
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Kuiper belt and Oort cloud surrounding the solar system.
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The Kuiper belt is
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a flat or donut-shaped distribution of distant comets around the Sun, extending out about 500 AU.
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The Oort cloud is
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a spherical distribution of distant comets around the Sun, extending out about 50,000 AU.
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Most comet nuclei are believed to be
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pieces of dusty ice left over from the formation of the solar system.
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The nucleus of Comet Halley, as seen on close-up photographs taken by the Giotto spacecraft, is
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potato-shaped and darker than coal.
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The measured diameter of the core of Comet Halley is about
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10 km
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Comet tails are the result of
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melting and evaporation of ices from the comet core.
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The gas and ion tail of a comet
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is always blown away from the comet in the anti-Sun direction by the solar wind.
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The ionized gas tail of a comet is always aligned along the
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comet-Sun line.
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Dust grains released by the melting of ice in a comet nucleus
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become a uniform, curved tail moving away from the comet under radiation pressure from sunlight.
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The orbits of periodic comets
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can extend far out beyond the orbit of Pluto and can be oriented in any direction in the solar system.
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The orbits of comets are
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randomly oriented in the solar system and can extend far beyond the orbit of Pluto
