您現在的位置: Language Tips> Audio & Video> Normal Speed News  
     





     
    Scientists discover 'tail' on distant star
    [ 2007-08-21 09:11 ]

    Download

    Images captured by a NASA science satellite reveal the star Mira has left in its wake a comet-like tail that is some 13 light years long — more than 120 trillion kilometers. It's a phenomenon that's never been seen before.

    The Galaxy Evolution Explorer satellite, known as Galex, was launched four years ago with the aim of studying the history of the universe, using a telescope equipped with ultraviolet detectors. Finding a gigantic tail on a fast-moving star was not something astronomers had anticipated. Chris Martin, the principal investigator on Galex, announced the discovery.

    "The Galaxy Evolution Explorer has discovered that Mira has a vast, turbulent tail stretching across interstellar space," Martin told reporters. "And it's truly remarkable that this star, which has been studied for centuries, has surprised us with a completely new and unexpected phenomenon."

    Mira's "tail" is composed of carbon, oxygen and other chemical elements. The discovery may help scientists understand how old, dying stars like Mira shed material that is later incorporated into new stars and planets. The astronomers calculate that the oldest parts of the tail were left behind tens of thousands of years ago, as the star grew and gravity weakened farther from its center.

    "In fact, if we had had, 30,000 years ago — If Neanderthal man had had ultraviolet eyes and could look above the atmosphere, he could have seen the beginning of this tail forming," said Martin.

    The age of the tail makes it something of a time capsule, says Columbia University astronomer Michael Shara, like the rings of a tree. "Because we have this tail that was generated over 30,000 years, we can look at small individual pieces of the tail and deduce what the mass loss rate was like and what the chemistry along the tail was, which gives us some hint as to the differentiation of elements in the atmosphere of Mira before it started to shed mass."

    In addition to the tail, images from the Galex satellite show a curved shock wave in front of Mira as it speeds through the surrounding space at 130 kilometers per second. Astronomer Mark Siebert of the Carnegie Institution says that the bow shock, as they call it, and the random-looking tail behind the star resemble a picture of a bullet in supersonic flight. "In front of the bullet there's a leading shock, much like Mira's bow shock. And then trailing the bullet there's also a classic turbulent wake, which is very reminiscent of the structures that we see behind Mira."

    Seibert says Mira is a very common type of star, so it may be that this kind of tail is actually not very rare and that more will be discovered. In any event, this one is the first.

    Shara, the Columbia University astronomer, says the new and completely unexpected discovery is an example of what can happen as astronomy advances.

    "Any time astronomers take a look at a new part of what we call observation space — that is, they start using a telescope which has much better angular resolution like Hubble, or much greater sensitivity in the ultraviolet like Galex, or a very large field of view like Galex — they tend to find something new, and that's exactly what's happened here," he said.

    The astronomers say they are really just beginning to study this huge structure. They published their discovery in the journal Nature.

    點擊進入更多VOA常速

    (來源:VOA  英語點津姍姍編輯

     

     
     
    相關文章 Related Stories
     
             
     
     
     
     
     
             

     

     

     
     

    48小時內最熱門

         
      “沒關系”怎么說
      《欲望城市》(精講十五)
      “逼供”怎么說
      打擊“盜版書”
      你會說“對不起”嗎

    本頻道最新推薦

         
      女孩的心思誰能猜:Suspended from class
      《說點什么吧》:Say something anyway
      Mountain and cowboy culture meet in Jackson Hole
      Livestock disease spreads in Britain
      Working magic in the garden with beans

    論壇熱貼

         
      雞蛋羹應該怎么來翻譯呢
      Winds will be from most directions?
      “老齡化社會”怎么翻
      你也老大不小了
      “洋氣”怎么說
      The Only Child Myth(e-c)practice






    亚洲午夜国产精品无码老牛影视| 无码的免费不卡毛片视频| 久久国产三级无码一区二区| 亚洲日韩中文字幕日韩在线| 精品人体无码一区二区三区| 中文字幕人妻无码专区| 人妻精品久久久久中文字幕69 | 亚洲熟妇少妇任你躁在线观看无码| 精品久久久无码21p发布| 亚洲VA中文字幕不卡无码| 本免费AV无码专区一区| 亚洲精品无码不卡在线播HE| 最近免费中文字幕大全免费版视频| 精品无码专区亚洲| 亚洲欧洲无码AV电影在线观看| 国产精品无码永久免费888 | 亚欧免费无码aⅴ在线观看| 日韩人妻无码精品无码中文字幕| 亚洲熟妇少妇任你躁在线观看无码 | 日韩精品无码免费专区午夜不卡| 久久亚洲中文字幕精品一区| av无码播放一级毛片免费野外| 亚洲成a人片在线观看无码| 无码福利一区二区三区| 被夫の上司に犯中文字幕| 精品无码人妻一区二区三区 | 最近中文字幕免费mv在线视频| 久久精品中文字幕大胸| 人妻少妇看A偷人无码精品| 草草久久久无码国产专区| 精品人妻无码一区二区色欲产成人| 免费无码又爽又刺激一高潮| 亚洲日本中文字幕天天更新| 视频一区二区中文字幕| 中文国产成人精品久久亚洲精品AⅤ无码精品 | 东京热无码av一区二区| 中文字幕乱码无码人妻系列蜜桃| 亚洲日韩在线中文字幕第一页| 狠狠精品干练久久久无码中文字幕 | 中文字幕av无码专区第一页| 中文字幕av高清有码|