(单词翻译:单击)
Question 9-19
Stars may be spheres,but not every celestial1 object is spherical2.Objects in the universe show a variety of shapes:round planets (some with rings),tailed comets,wispy cosmic gas and dust clouds,ringed nebulae,pinwheel-shaped spiral galaxies3,and so on.But none of the shapes on this list describes the largest single entities4 in the universe.These are the double radio sources,galaxies with huge clouds of radio emission5 that dwarf6 the visible galaxies,sometimes by a factor of a hundred or more.Stretching over distances greater than a million light-years,these radio-emitting regions resemble twin turbulent gas clouds,typically forming dumbbell-like shapes with the visible galaxy7 (when it is visible)in the center.
These double radio sources present astronomers8 with a puzzle.Their radio emission arises from the synchrotron process,in which electrons accelerated to nearly the speed of light move through magnetic fields.However,in view of the rate at which the radio sources emit energy,they should disappear in a few million years as their electrons slow down and cease producing radiation.Somehow new electrons must be continually accelerated to nearly the speed of light,otherwise,by now almost none of the double radio sources would be observed.
With the advent9 of high-resolution radio interferometers during the late 1970's,part of the answer became clear:the electrons are produced in jets that are shot out in opposite directions from the center of galaxy.Remarkably10 narrow and highly directional,the jets move outward at speeds close to the speed of light.When the jets strike the highly rarefied gas that permcales intergalactic space,the fast-moving electrons lose their highly directional motion and form vast clouds of radio-emitting gas.
Cosmic jets have ranked among the hottest topics of astronomical11 research in recent years as astronomers strive to understand where they come from.Why should a galaxy eject matter at such tremendous speeds in two narrow jets?And why are such jets not seen in the Milky12 Way?
9.The word "celestial"in line 1could best be replaced by(A)visible
(B)astronomical
(C)glowing
(D)scientific
10.The word "entities"in line 4is closest in meaning to
(A)factors
(B)processes
(C)objects
(D)puzzles
11.In the first paragraph,the author describes objects in the universe in terms of their
(A)color
(B)origin
(C)location
(D)shape
12.Which of the following is the best representation of the clouds of radio emission described in the first paragraph?
(A)(图)
(B)(图)
(C)(图)
(D)(图)
13.According to the passage,scientists do not fully13 understand why double radio sources(A)have not eventually disappeared
(B)cannot be observed with a telescope
(C)are beginning to slow down
(D)are not as big as some planets and stars
14.The word "their"in line 22refers to
(A)speeds
(B)directions
(C)electrons
(D)clouds
15.According to the passage,what happens when electrons and gas collide in space?
(A)The gas becomes more condensed
(B)The gas becomes less radiated
(D)The electrons become negatively charged
16.The author suggests that astronomers consider the study of cosmic jets to be
(A)an obsolete15 scientific field
(B)an unprofitable venture
(C)an intriguing16 challenge
(D)a subjective17 debate
17.In what lines does the passage compare the size of double radio sources with that of other galaxies?
(A)Lines 4-6
(B)Lines 12-14
(C)Lines 19-20
(D)Lines 23-24
18.Where in the passage does the author mention a technology that aided in the understanding of double radio sources?
(A)Line 2
(B)Line 7
(C)Line 17
(D)Line 21
1
celestial
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adj.天体的;天上的 | |
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2
spherical
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adj.球形的;球面的 | |
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3
galaxies
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星系( galaxy的名词复数 ); 银河系; 一群(杰出或著名的人物) | |
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4
entities
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实体对像; 实体,独立存在体,实际存在物( entity的名词复数 ) | |
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5
emission
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n.发出物,散发物;发出,散发 | |
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6
dwarf
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n.矮子,侏儒,矮小的动植物;vt.使…矮小 | |
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7
galaxy
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n.星系;银河系;一群(杰出或著名的人物) | |
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8
astronomers
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n.天文学者,天文学家( astronomer的名词复数 ) | |
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9
advent
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n.(重要事件等的)到来,来临 | |
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10
remarkably
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ad.不同寻常地,相当地 | |
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11
astronomical
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adj.天文学的,(数字)极大的 | |
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12
milky
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adj.牛奶的,多奶的;乳白色的 | |
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fully
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adv.完全地,全部地,彻底地;充分地 | |
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14
disperse
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vi.使分散;使消失;vt.分散;驱散 | |
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obsolete
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adj.已废弃的,过时的 | |
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intriguing
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adj.有趣的;迷人的v.搞阴谋诡计(intrigue的现在分词);激起…的好奇心 | |
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17
subjective
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a.主观(上)的,个人的 | |
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