2018年12月英语四级听力练习(6)

来源:步知资讯 时间:10-31 阅读:


  2018年12月英语四六级考试在即,步知网(www.buzhi.com)为大家整理了短文听力练习,真题听力练习等听力练习,希望大家认真备考,一步及格。所有听力练习音频,关注公众号点击词汇句型就可查看。

image.png

  The human eye is unable to see black holes in space. But telescopes with special tools can help find black holes by seeing how they affect nearby stars.

  In February, the Japanese space agency sent its Astro-H satellite into orbit around the Earth. The satellite's job was to examine large structures in space, like huge black holes that exist at the center of most galaxies.

  Galaxies are large groups of stars. Scientists estimate there are between 100 and 200 billion galaxies in the universe.

  The Astro-H satellite fell apart after only a month in space. But in that short time, Astro-H was able to gather important information. It sent back data about the Perseus cluster – a grouping of galaxies in the star constellation Perseus. The Perseus cluster is home to hundreds of galaxies. They are 240 million light years from Earth.

  Black holes are areas where the pull of gravity is so strong that not even light can escape. Usually they happen after very big, supergiant stars explode. The exploded star turns into something called a "supernova." It is very bright, but short-lived. Supernovas create the largest explosions in space.

  The material remaining after the supernova explosion collapses. Gravity pulls, or crushes, all the matter into a very small space. When light can no longer escape that space, it is known as a black hole.

  The Japanese satellite Astro-H was carrying an instrument called an X-ray spectrometer. It was able to measure the way gas flows at the center of the Perseus cluster.

  What it found was that the superheated gas at the center of the cluster flowed more calmly than researchers expected. And that told them something about how black holes work, and how galaxies are formed.

  Brian McNamara is an astrophysicist with the University of Waterloo in Canada.

  "And that gives us a very precise measurement of how much energy is being pumped into this gas by supermassive black holes, and so it allows us to form a more complete picture of how galaxies evolve, how the stars and the gas that will eventually cool out like rain to form the stars, evolves over cosmic time."

  The scientists are also looking at the hot plasma — another kind of matter — and gases that surround galaxies.

  "This is gas that has not cooled out and condensed out like rain in our atmosphere to form stars, planets, life, for example. So it's the potential for the future, and we're trying to understand what the future destiny of this galaxy and many other galaxies would be."

  McNamara says that supermassive black holes may change how galaxies form and change over time.

  "The energy released by these giant black holes is very tightly coupled to these atmospheres, which is the stuff out of which future stars will form."

  And what that means, he says, is that these huge black holes can affect the rate at which a galaxy grows.

  I'm Anne Ball.


  Words in This Story

  galaxy – n. 星系,银河系

  Perseus cluster – n. 英仙座星系团

  x-ray spectrometer – n. X射线光谱仪

  cosmic – adj. 宇宙的

  constellation – n. 星座,星群

  supergiant – adj. 超大的

  precise – adj. 精确的,明确的

  eventually – adv. 最后,终于

  condensed – adj. 浓缩的,扼要的

  potential – n. 潜在,可能性

责任编辑:yn

相关推荐
① "步知网"上的内容(含文章、资料、资讯等), 本网注明"来源:步知网"的,版权均为"步知网"或步知公考所有,任何公司、媒体、网站或个人未经授权不得转载、链接、转贴或以其他方式使用。已授权许可的媒体、网站,在使用时必须注明"稿件来源:步知网",违者本网站将依法追究责任。
② 未注明来源:步知网"的文章、资料、资讯等,均为网络转载稿,本网站转载出于传递更多信息之目的,并不意味着赞同其观点或证实其内容的真实和准确性。如其他媒体、网站或个人从本网站转载使用,必须保留本网站注明的"稿件来源",并自负版权等法律责任。如擅自篡改为"来源:步知网",本站将依法追究其法律责任。
③ 如本网转载稿涉及版权等问题,请原作者见稿后在两周内与步知网联系。