单项选择题

第三篇
Small But Wise
On December 14, NASA1 blasted a smallbut mighty telescope into space. The telescope is called WISE and is about aswide around as a trashcan. Don’t let its small size fool you: WISE has apowerful digital camera, and it will be taking pictures of some the wildestobjects2 in the known universe,including asteroids, faint stars, blazing galaxies3 and giant clouds of dustwhere planets and stars are born.
“I’mvery excited because we’re going to be seeing parts of the universe that wehaven’t seen before, ” said Ned Wright, a scientist who directs the WISE project.
Since arriving in space, the WISEtelescope has been circling the Earth, held by gravity in a polar orbit4( thismeans it crosses close to the north and south poles with each lap5). Its camerais pointed outward, away from the Earth, and WISE will snap a picture of adifferent part of the sky every 11 minutes. After six months it will have takenpictures across the entire sky.
The pictures taken by WISE won’t be likeeveryday digital photographs, however. WISE stands for “Wide-field InfraredSurvey Explorer. ” As its name suggests, the WISE camera takes pictures offeatures that give off infrared radiation6.
Radiation is energy that travels as awave. Visible light, including the familiar spectrum of light7 that becomesvisible in a rainbow, is an example of radiation. When an ordinary digitalcamera takes a picture of a tree, for example, it receives the waves of visiblelight that are reflected off the tree. When these waves enter the camerathrough the lens, they’re processed by the camera, which then puts the imagetogether.
Waves of infrared radiation are longerthan waves of visible light, so ordinary digital cameras don’t see them, andneither do the eyes of human beings. Although invisible to the eye, longerinfrared radiation can be detected as warmth by the skin.
That’s a key idea to why WISE will beable to see things other telescopes can’t. Not everything in the universe showsup in visible light. Asteroids, for example, are giant rocks that float throughspace — but they absorb most of the light that reaches them. They don’t reflectlight, so they’re difficult to see. But they do give off infrared radiation, soan infrared telescope like WISE will be able to produce images of them. Duringits mission WISE will take pictures of hundreds of thousands of asteroids. 　　Brown dwarfs8 are another kind ofdeep-space object that will show up in WISE’s pictures. These objects are“failed” stars — which means they are not massive enough to jump start9 thesame kind of reactions that power stars such as the sun. Instead, brown dwarfssimply shrink and cool down. They’re so dim that they’re almost impossible tosee with visible light, but in the infrared spectrum they glow.

It can beinferred from the last paragraph that brown dwarfs.（）

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