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  3. The temperature of the Sun is over 5,000 degrees Fahrenheit at the surface, but it rises to perhaps more than 16 million degrees

The temperature of the Sun is over 5,000 degrees Fahrenheit at the surface, but it rises to perhaps more than 16 million degrees

admin2010-08-04  97
问题     The temperature of the Sun is over 5,000 degrees Fahrenheit at the surface, but it rises to perhaps more than 16 million degrees at the center. The Sun is so much hotter than the Earth that matter can exist only as a gas, except all the core. In the core of the Sun, the pressures are so great against the gases that, despite the high temperature, there may be a small solid core. However, no one really knows, since the center of the Sun can never be directly observed.
    Solar astronomers do know that the Sun is divided into five layers or zones. Starting at the outside and going down into the Sun, the zones are the corona (光环圈), chromospheres (色环层), photosphere, convection zone, and finally the core. The first three zones are regarded as the Sun’s atmosphere. But since the Sun has no solid surface, it is hard to tell where the atmosphere ends and the main body of the Sun begins.
    The sun’s outermost layer begins about 10,000 miles above the visible surface and goes outward for millions of miles. This is the only part of the Sun that can be seen during an eclipse. such as the one in February 1979. At any other time, the corona can be seen only when special instruments are used on cameras and telescopes to shut out the glare of the Sun’s rays.
    The corona is a brilliant, pearly white, filmy light, about as bright as the full Moon. Its beautiful rays are a sensational sight during an eclipse. The corona’s rays flash out in a brilliant fan that has wispy (稀疏的) spikelike (穗状的) rays near the Sun’s north and south poles. The corona is the thickest at the sun’s equator.
    The corona rays are made up of gases streaming outward at tremendous speeds and reaching a temperature of more than 2 million degrees Fahrenheit.  The rays of gas thin out as they reach the space around the planets. By the time the Sun’s corona rays reach the Earth, they are weak and invisible.
As it is used in the passage, the word "photosphere’’ (Line 2, Para. 2) means ______.
选项 A、a scarlet gaseous envelope surrounding the Sun
B、the luminous envelope of gas surrounding the Sun
C、the mixture of gasses that surrounds any planet or star
D、the luminous irregular envelope of highly ionized gas outside the chromospheres of the Sun
答案B
解析 语义题。文中关于“photosphere”的说明只在第二段后半部分见到：作者指出，太阳从外到内分别是corona(日冕)，chromospheres(色环层)，和photosphere，然后作者又指出“The first three zones are regarded as the Sun’s atmosphere．”photosphere也是太阳大气层中的一层，所以它应该是一种气体。A说它是一种“气体状包层”，不够准确。C内容与本文无关，错误。D选项将 photosphere和chromospheres的位置搞反了，也错。
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