问题 问答题 简答题

什么是星系?

答案

参考答案:

由无数恒星和星际物质构成的巨大集合体称为星系。它们的尺度可以从几千到几十万光年。星系或称恒星系,是宇宙系统中的重要一环。星系数量众多。到目前为止,人们已在宇宙中观测到了约1000亿个星系。地球就处在由1000多亿颗恒星以及银河星云组成银河系中。有的星系离银河系较近,可以清楚地观测到它们的结构。离银河系最近的星系——大麦哲伦星云和小麦哲伦星云,距离为十几万光年。有的非常遥远,目前所知最远的星系离我们有近150亿光年。

人们把目前所认识到的宇宙部分,包括已观测到的所有星系,称为总星系。

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     As science develops rapidly in the direction of technology,it supplies man a better and more comfortable   1  . Men will be   2  shorter and shorter hours,    3    housewives will also be able to have   4    time.
Can you     5    doing housework without a housewife? Scientists believe this will     6   into realities in not
very long time,and perhaps during your life time house-robots will take   7   of housewives.
    When  I     8    this kind of machine with housewives,some 90 percent of them replied     9     ,"     10   
 can I buy one?"      11     10 percent said,"I would be terrified to see it     12     about my house. " But
when I     13     to them that it could be turned    14    or stopped,they quickly realized that it is a    15    
object.
      In my own  16  we have found that the washing-up machine is regarded as a good     17    in the room. There's no greater   18    than to go to bed in the evening and     19    that the washing-up is being done
downstairs after we are   20   .
      Some families would   21   to have their robot slaves   22   all the downstairs housework after they
were in   23   at night,while others would have it   24   in the momings. But this would be entirely matter
of   25   .
( )1. A. machine    
( )2. A. living      
( )3. A. even though
( )4. A. more free  
( )5. A. think      
( )6. A. be made    
( )7. A. place      
( )8. A. discussed  
( )9. A. coolly      
( )10.  A.  How long
( )11. A. Other      
( )12. A. moving    
( )13. A. wrote      
( )14. A. into      
( )15. A. terrible  
( )16. A. home      
( )17. A. furniture  
( )18. A. trouble    
( )19. A. know      
( )20. A. home      
( )21. A. use        
( )22. A. to do      
( )23. A. work      
( )24. A. to do      
( )25. A. choice    
B. house      
B. resting    
B. while      
B. shorter    
B. enjoy      
B. be tumed    
B. places      
B. supplied    
B. immediately
B.  How much  
B. Another    
B. talking    
B. showed      
B. on          
B. useful      
B. opimon      
B. pet        
B. pleasure    
B. feel        
B. tired      
B. rather      
B. doing      
B. bed        
B. doing      
B. practice    
C. life      
C. working  
C. however  
C. busier    
C. infer    
C. go        
C. a place  
C. helped    
C. politely  
C.  How soon
C. The other
C. jumping  
C. spoke    
C. over      
C. real      
C. future    
C. hand      
C. choice    
C. notice    
C. out      
C. feellike  
C. done      
C. need      
C. done      
C. idea      
D. sleep        
D. sleeping    
D. so          
D. a good      
D. imagine      
D. be produced  
D. the place    
D. sold        
D. slowly      
D.  How often  
D. Others      
D. playing      
D. explained    
D. off          
D. future      
D. time        
D. person      
D. object      
D. find        
D. asleep      
D. like        
D. wash        
D. house        
D. do          
D. quality