日日天干夜夜人人添,日本中文一区免费观看,久久99综合精品国产首页,中文字幕无码乱人伦

  首頁 課程  書店 學校  題庫 論壇  網(wǎng)校  地方分站: 北京 | 上海 | 鄭州 | 天津
 新托福考試網(wǎng)
 考試資訊  報考指南  備考寶典  考場經(jīng)驗  閱讀輔導  真題  模擬題   學友圈   精品網(wǎng)校課程
   聽力 | 寫作 | 閱讀 | 口試   北京新航道托福精品課程   環(huán)球雅思托福熱門課程   新東方托福網(wǎng)絡課程   啟德托福   托福考試答疑區(qū)

托福閱讀:黑洞 Black Holes

作者:不詳   發(fā)布時間:2010-04-27 15:44:50  來源:網(wǎng)絡
  • 文章正文
  • 網(wǎng)校課程
  • 資料下載
  • 熱門話題
  • 論壇

  在遙遠的外太空有許多神秘的天體,黑洞就是其中之一。至今依然有科學家對于黑洞的存在性持有質(zhì)疑的觀點,但是大部分的天文學家還是相信射電望遠鏡的觀測數(shù)據(jù),對黑洞的存在表示認同。從今天起我們將分三次連載這篇關于黑洞的科技文,希望對提高大家的閱讀能力有所幫助。

  Astronomers think the object shown in this Chandra X-ray Observatory image (in box) may be an elusive intermediate-mass black hole. Located about 32 million light-years from Earth in the Messier 74 galaxy (M74), this object emits periodic bursts of x-rays at a rate that suggests it is much larger than a stellar-mass black hole but significantly smaller than the supermassive black holes found at the centers of galaxies. Few such middling black holes have been discovered, and scientists aren't sure how they form.

  Black holes are the cold remnants of former stars, so dense that no matter—not even light—is able to escape their powerful gravitational pull.

  While most stars end up as white dwarfs or neutron stars, black holes are the last evolutionary stage in the lifetimes of enormous stars that had been at least 10 or 15 times as massive as our own sun.

  When giant stars reach the final stages of their lives they often detonate in cataclysms known as supernovae. Such an explosion scatters most of a star into the void of space but leaves behind a large "cold" remnant on which fusion no longer takes place.

熱門資料下載:
新托?荚囌搲療豳N:
【責任編輯:育路編輯  糾錯
新托福培訓咨詢電話:010-51294614
報考直通車
 
·新托福最近考試時間:2010年6月26日。
·考試內(nèi)容:閱讀、 聽力、口語、寫作。
課程推薦
                   
 新托?荚囕o導