問題詳情

請回答第 46 題至第 48 題：A brown dwarf is a dim, hypothetical type of star that astronomers have long thought must exist, but firm proof thatit does has so far eluded them. The problem is simply that, by definition, a brown dwarf is maddeningly difficult to see.So astronomers have resorted to rather indirect methods of detection. They have tried to find a dwarf whose gravity iscausing a bright star nearby to wobble. Or they have picked a bright star that should be emitting a certain amount of lightand looked to see if a dwarf companion is adding a little extra. Now the astronomer William Forrest of the University ofRochester has apparently succeeded in a direct approach: he says he has simply taken a picture of one—in fact, not just ofone but of several.It was not quite as easy as it sounds. A brown dwarf has less than 8 percent of the sun’s mass, which means it is notmassive enough to squeeze its core enough to keep fusion reactions going. In other words, it is not a proper star at all; theonly radiation it gives off is heat left over from its birth in a collapsing cloud of interstellar gas. With no internal reactor,the star quickly cools and gets too dim and brown to see.
46 According to the passage, what does a brown dwarf refer to?
(A)A bright star
(B)A star eight times larger than the sun
(C)A dim mass with no internal reactor
(D)A star with fusion reactions going

參考答案

答案：C
難度：適中0.5
統計：A(11),B(20),C(41),D(9),E(0)

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