邻近星系的紫外光照片提供了早期宇宙的线索英文原文
译:
Jack


  天文学家们利用这张照片,想要探究遥远的星系具有如此之怪的形状的缘由。的确,这些星系的模样,和我们看见的邻近星系的椭圆星系或是漩涡星系有着显著的区别。

  那些遥远的星系的模样看起来很怪,难道它们真正的模样真的很怪?还是它们本身的样子并不怪,只是天文学家们没有把照片拍好,只弄到了星系中最亮的一部分呢?那些星系发出的光,走过了十分遥远的空间(几十亿光年),继而到达地球上。在光向地球传播的过程中,由于宇宙的膨胀,光波被拉长了(波长变长),结果,那些光便变成了我们目前的仪器尚无能为力的红外光。天文学家们能看见的唯一的光线,就是那些由于光波被拉长从而形成可见光的紫外线。依靠那些紫外线,天文学家们能够看见那些年轻炙热的恒星的所在。那些星系,就像要从一幅残缺的画中猜出那幅画的原貌,那并不是一件容易的事。

  到底遥远的星系是什么样的呢?天文学家们为了找出答案,研究了临近的37个星系。他们将那些临近的星系和它们的“远房亲戚”作了比较,这些由宽视场行星照相机2拍摄的照片,向我们提供了有代表性的样品。天文学家们观察了那些紫外光区的星系,并且研究了星系中的那些恒星。天文学家们正在遥远的星系的“冰山顶”上探索,他们观察出的结果证明了这种说法。并不是那些遥远的星系本身就具有奇特的形状,我们可以凭借这张哈勃拍摄的照片说。目前,这个结果已经在第197届美国天文学会会议上宣布了。


                 


  左边的NGC 3310的照片的中心部分即旋涡状星系的星暴区,向我们展示了年轻和年老的恒星的均匀的分布。如果大部分的星系都是这种情况的话,天文学家们就能轻松地认出遥远的星系。但是,在大多数星系中,由于时间的关系,那些恒星渐渐地互相分离,使得对星系的区分更加困难。NGC 3310距地球约46,000,000光年远,在大熊座。这张照片摄于2000年9月12~13日。

  处于中间的是一个小而年轻的旋涡状星系。ESO 418-008是天文学家们在观测矮星系时“推荐”出的一个代表。这些星系要比像我们银河系一样的典型星系要小得多。在这个星系中,时间对恒星的分离作用更为显著,那些年老的恒星(红色)处于中间,而年轻的恒星(蓝色),则存在于星系的旋臂中。这些小而年轻的星系,可能是由于形成时遇到了障碍。ESO 418-008处于距地球56,000,000光年的天炉座中。照片摄于2000年10月10日。

  而右边那张照片显现了两个星系——UGC 06471和UGC 06472之间的冲撞。在早期的宇宙中,这种冲撞显得十分常见,而正是这种冲撞,形成了一部分形状奇特的星系。在对宇宙进行的深度观测中,哈勃望远镜找到了很多这样的星系。这些星系合并的紫外光照片,向我们表明,在星系冲撞之前或者之后,那些大质量的恒星产生了大量的尘埃。这些尘埃,使得那些恒星的光看起来变红,就像在日落时那些满是灰尘的大气将太阳光散射,使之看起来变红了。天文学家们研究临近的星系的冲撞,有可能帮助他们解释我们看见的遥远的星系的奇特的形状。UGC 06471和UGC 06472距地球约145,000,000光年,在大熊座中。这张照片摄于2000年9月11日。

 

   译自 摘自哈勃网站(http://oposite.stsci.edu

Hubble's Ultraviolet Views of Nearby Galaxies Yield Clues to Early Universe
Chinese Version

  Astronomers are using these three NASA Hubble Space Telescope images to help tackle the question of why distant galaxies have such odd shapes, appearing markedly different from the typical elliptical and spiral galaxies seen in the nearby universe. 

  Do faraway galaxies look weird because they are truly weird? Or, are they actually normal galaxies that look like oddballs, because astronomers are getting an incomplete picture of them, seeing only the brightest pieces? Light from these galaxies travels great distances (billions of light-years) to reach Earth. During its journey, the light is "stretched" due to the expansion of space. As a result, the light is no longer visible, but has been shifted to the infrared where present instruments are less sensitive. About the only light astronomers can see comes from regions where hot, young stars reside. These stars emit mostly ultraviolet light. But this light is stretched, appearing as visible light by the time it reaches Earth. Studying these distant galaxies is like trying to put together a puzzle with some of the pieces missing. 

  What, then, do distant galaxies really look like? Astronomers studied 37 nearby galaxies to find out. By viewing these galaxies in ultraviolet light, astronomers can compare their shapes with those of their distant relatives. These three Hubble telescope pictures, taken with the Wide Field and Planetary Camera 2, represent a sampling from that survey. Astronomers observed the galaxies in ultraviolet and visible light to study all the stars that make up these "cities of stars." The results of their survey support the idea that astronomers are detecting the "tip of the iceberg" of very distant galaxies. Based on these Hubble ultraviolet images, not all the faraway galaxies necessarily possess intrinsically odd shapes. The results are being presented today at the 197th meeting of the American Astronomical Society in San Diego, CA. 

  The central region of the "star-burst" spiral galaxy at far left, NGC 3310, shows young and old stars evenly distributed. If this were the case with most galaxies, astronomers would be able to recognize faraway galaxies fairly easily. In most galaxies, however, the stars are segregated by age, making classifying the distant ones more difficult. NGC 3310 is 46 million light-years from Earth in the constellation Ursa Major. The image was taken Sept. 12-13, 2000. 

  The middle image is an example of a tiny, youthful spiral galaxy. ESO 418-008 is representative of the myriad of dwarf galaxies astronomers have seen in deep surveys. These galaxies are much smaller than typical ones like our Milky Way. In this galaxy, the population of stars is more strongly segregated by age. The older stars [red] reside in the center; the younger [blue], in the developing spiral arms. These small, young galaxies may be the building blocks of galaxy formation. ESO 418-008 is 56 million light-years from Earth in the southern constellation Fornax. The image was taken Oct. 10, 2000. 

  The picture at right shows a cosmic collision between two galaxies, UGC 06471 and UGC 06472. These collisions occurred frequently in the early universe, producing galaxies of unusual shapes. The Hubble telescope has spied many such galaxies in the deep field surveys. The ultraviolet images of this galaxy merger suggest the presence of large amounts of dust, which were produced by massive stars that formed before or during this dramatic collision. This dust reddens the starlight in many places, just like a dusty atmosphere reddens the sunset. Studying the effects of this nearby collision could help astronomers explain the peculiar shapes seen in some of the distant galaxies. UGC 06471 and UGC 06472 are 145 million light-years from Earth in the constellation Ursa Major. The image was taken July 11, 2000.

STScI-PRC01-04
January 11, 2001

 

   Copied From Hubble Web(http://oposite.stsci.edu

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