雅思阅读准备宇宙探索之超级地球

　　New Planet System Found—May Have Hidden "Super Earth"

　　An artist's impression of two Saturn-like planets orbiting the star Kepler-9.

　　Image courtesy NASA

　　Rachel Kaufman

　　for National Geographic News

　　Published August 26, 2010

　　A newly discovered planetary system orbiting a sunlike star may conceal a rare super-Earth, according to data from NASA's Kepler space telescope.

　　Launched last March, Kepler was designed to look for extrasolar planets, aka exoplanets, via transits—the periodic dimming of light from stars due to planets passing in front them, as seen from the telescope's vantage point. (Read about Kepler's first planet discoveries.)

　　After analyzing seven months' worth of data from Kepler, a team led by Matt Holman of the Harvard-Smithsonian Center for Astrophysics found two transiting exoplanets orbiting the star Kepler-9, which lies about 2,300 light-years from Earth.

　　One of the planets, dubbed Kepler-9b, takes just over 19 days to orbit its star. The other, Kepler-9c, takes almost 39 days to complete an orbit. (Find out how exoplanets get their names.)

　　The researchers noticed that both planets' orbital periods speed up and slow down at regular intervals. This means the two planets are locked in gravitational "resonance"—so that each planet's gravity is affecting the other's orbit.

　　Using that data, the scientists were able to calculate the masses of the planets, and they found that both worlds are slightly less massive than Saturn.

　　Newfound Planet System Includes a Hot Earth?

　　When the astronomers accounted for the amount of stellar dimming the two planets should cause, they found another, faint source of interference.

　　This signal could mean that a third planet, smaller and nearer to the host star, is transiting Kepler-9 every 1.6 days. The third planet would be about 1.5 times the mass of Earth and made of rocks rather than gas.

　　(Related: "Newfound Alien Star System Boasts Five, Maybe Seven, Planets.")

　　But the researchers aren't celebrating just yet—interference from background stars or stellar companions can look a lot like the signals of transiting exoplanets.

　　"At this point, we have a very, very interesting candidate, and I hope soon we may be able to see something more," Holman said. (Read about the search for new Earths in National Geographic magazine.)

　　And even if the unknown object turns out to be a super-Earth, humans won't likely be colonizing it: Based on its tight orbit, the planet's surface temperature would be about 2,200 Kelvin (3,500 degrees F, or 1,900 degrees C).

　　(Related: "'Super Earth' May Really Be New Planet Type: Super-Io.")

　　The newfound planetary system is described in this week's issue of the journal Science.

　　雅思阅读的题型一直是考生比较关注的问题，分析认为主要有以下两个原因：

　　1. 有相对简单和相对费时的题型;

　　2.每个考生都有自己擅长的和较害怕的题型。具体来说：对于词汇不足的考生可能最害怕段落标题匹配题及摘要归纳填空题;对于词汇量较大的考生来说，是非无判断题，段落标题匹配题和摘要归纳填空题可能是比较简单的。选择题和其它匹配题是相对来说比较费时的，所以大部分考生都很害怕这类题型。

　　那么，面对上面所提到的这些情况，考生应该在题型方面怎样备考呢?

　　首先，专家认为考生必须从心理上准备迎接所有的题型，在备考中要尽可能喜欢所有题型。有的考生会一次次地祈祷：“希望这次考试不要有选择题或段落细节信息定位题!”这样做，其实是无形中给自己制造了负面的影响。考试题型不是我们所能预料和控制的，一旦有了上述心理，很有可能一看到题型就慌了，一开始就没有一个好的状态。还有一部份考生喜欢跟着考题回忆和机经走，看到上次考了什么题就在备考中只关注那些题型。考题回忆和机经可以看看，但只能做参考，考生千万不要被它们所左右。否则就是自己给自己制造障碍。

　　其次，考生必须对各类题型的题型特点和答题注意事项了如指掌。雅思阅读考试时间之短，文章之学术性，题量之大，题型之多等特点决定了考生势必会感觉时间不够。考生要在有限的时间内答完所有的题并尽可能地保证较高的正确率确实不是一件容易的事情。考生除了要有一定的词汇量和阅读速度之外，常见的雅思阅读技巧和解题策略是必须的。而解题策略很多时候是建立在考生熟悉题型特点的基础之上的。比如说，考生拿到一篇文章绝不是从第1题接到13题，而是应该分析各组题型的特点和难易，由易到难。同样，考生也可以根据3篇各自的题型来初步判断哪一篇的题型可能对自己比较有利，那篇可能较难，以便能灵活地采取合适的策略。

　　最后，专家建议考生在考前进行练习时，不要光做套题，而应该偶尔穿插一些专题的练习，重点练习自己没什么把握的题型。注意练习时时间的掌控是很重要的，不要给自己30分钟完成6道是非无，那样不能达到训练的目的，不能保证良好的效果。