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 that
it 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 is
causing a bright star nearby to wobble. Or they have picked a bright star that should be emitting a certain amount of light
and looked to see if a dwarf companion is adding a little extra. Now the astronomer William Forrest of the University of
Rochester has apparently succeeded in a direct approach: he says he has simply taken a picture of one—in fact, not just of
one 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 not
massive enough to squeeze its core enough to keep fusion reactions going. In other words, it is not a proper star at all; the
only 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.
【題組】47 Which of the following is one of the indirect approaches to detect a brown dwarf?
(A)To simply take a picture of it
(B)To compare its weight to a nearby star’s
(C)To see if a star nearby is quavered by the gravity of a dwarf
(D)To see if extra light is added to a dwarf by a certain bright star
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