太阳系存在很多宜居星球
文章来源:未知 文章作者:enread 发布时间:2012-12-04 07:30 字体: [ ]  进入论坛
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Scattered1 around the Milky2 Way are stars that resemble(类似) our own sun -- but a new study is finding that any planets orbiting those stars may very well be hotter and more dynamic than Earth. That's because the interiors of any terrestrial planets in these systems are likely warmer than Earth -- up to 25 percent warmer, which would make them more geologically active and more likely to retain enough liquid water to support life, at least in its microbial form.
 
The preliminary finding comes from geologists3 and astronomers4 at Ohio State University who have teamed up to search for alien life in a new way.
 
They studied eight "solar twins" of our sun -- stars that very closely match the sun in size, age, and overall composition -- in order to measure the amounts of radioactive elements they contain. Those stars came from a dataset recorded by the High Accuracy Radial Velocity5 Planet Searcher spectrometer at the European Southern Observatory6 in Chile.
 
They searched the solar twins for elements such as thorium and uranium, which are essential to Earth's plate tectonics because they warm our planet's interior. Plate tectonics helps maintain water on the surface of Earth, so the existence of plate tectonics is sometimes taken as an indicator7 of a planet's hospitality to life.
 
Of the eight solar twins they've studied so far, seven appear to contain much more thorium than our sun -- which suggests that any planets orbiting those stars probably contain more thorium, too. That, in turn, means that the interior of the planets are probably warmer than ours.
 
For example, one star in the survey contains 2.5 times more thorium than our sun, said Ohio State doctoral student Cayman Unterborn. According to his measurements, terrestrial planets that formed around that star probably generate 25 percent more internal heat than Earth does, allowing for plate tectonics to persist longer through a planet's history, giving more time for live to arise.
 
"If it turns out that these planets are warmer than we previously8 thought, then we can effectively increase the size of the habitable zone around these stars by pushing the habitable zone farther from the host star, and consider more of those planets hospitable9 to microbial life," said Unterborn, who presented the results at the American Geophysical Union meeting in San Francisco this week.
 
"At this point, all we can say for sure is that there is some natural variation in the amount of radioactive elements inside stars like ours," he added. "With only nine samples including the sun, we can't say much about the full extent of that variation throughout the galaxy10. But from what we know about planet formation, we do know that the planets around those stars probably exhibit the same variation, which has implications for the possibility of life."


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1 scattered 7jgzKF     
adj.分散的,稀疏的;散步的;疏疏落落的
参考例句:
  • Gathering up his scattered papers,he pushed them into his case.他把散乱的文件收拾起来,塞进文件夹里。
2 milky JD0xg     
adj.牛奶的,多奶的;乳白色的
参考例句:
  • Alexander always has milky coffee at lunchtime.亚历山大总是在午餐时喝掺奶的咖啡。
  • I like a hot milky drink at bedtime.我喜欢睡前喝杯热奶饮料。
3 geologists 1261592151f6aa40819f7687883760a2     
地质学家,地质学者( geologist的名词复数 )
参考例句:
  • Geologists uncovered the hidden riches. 地质学家发现了地下的宝藏。
  • Geologists study the structure of the rocks. 地质学家研究岩石结构。
4 astronomers 569155f16962e086bd7de77deceefcbd     
n.天文学者,天文学家( astronomer的名词复数 )
参考例句:
  • Astronomers can accurately foretell the date,time,and length of future eclipses. 天文学家能精确地预告未来日食月食的日期、时刻和时长。 来自《简明英汉词典》
  • Astronomers used to ask why only Saturn has rings. 天文学家们过去一直感到奇怪,为什么只有土星有光环。 来自《简明英汉词典》
5 velocity rLYzx     
n.速度,速率
参考例句:
  • Einstein's theory links energy with mass and velocity of light.爱因斯坦的理论把能量同质量和光速联系起来。
  • The velocity of light is about 300000 kilometres per second.光速约为每秒300000公里。
6 observatory hRgzP     
n.天文台,气象台,瞭望台,观测台
参考例句:
  • Guy's house was close to the observatory.盖伊的房子离天文台很近。
  • Officials from Greenwich Observatory have the clock checked twice a day.格林威治天文台的职员们每天对大钟检查两次。
7 indicator i8NxM     
n.指标;指示物,指示者;指示器
参考例句:
  • Gold prices are often seen as an indicator of inflation.黃金价格常常被看作是通货膨胀的指标。
  • His left-hand indicator is flashing.他左手边的转向灯正在闪亮。
8 previously bkzzzC     
adv.以前,先前(地)
参考例句:
  • The bicycle tyre blew out at a previously damaged point.自行车胎在以前损坏过的地方又爆开了。
  • Let me digress for a moment and explain what had happened previously.让我岔开一会儿,解释原先发生了什么。
9 hospitable CcHxA     
adj.好客的;宽容的;有利的,适宜的
参考例句:
  • The man is very hospitable.He keeps open house for his friends and fellow-workers.那人十分好客,无论是他的朋友还是同事,他都盛情接待。
  • The locals are hospitable and welcoming.当地人热情好客。
10 galaxy OhoxB     
n.星系;银河系;一群(杰出或著名的人物)
参考例句:
  • The earth is one of the planets in the Galaxy.地球是银河系中的星球之一。
  • The company has a galaxy of talent.该公司拥有一批优秀的人才。
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