Hubble Goes to the eXtreme to Assemble Farthest Ever View of the Universe

源地址：http://hubblesite.org/newscenter/archive/releases/2012/37/image/a/

                               
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ABOUT THIS IMAGE:Like photographers assembling a portfolio of best shots, astronomers have assembled a  new, improved portrait of mankind's deepest-ever view of the universe.
Called the eXtreme Deep Field, or XDF, the photo was assembled by combining 10 years  of NASA Hubble Space Telescope photographs taken of a patch of sky at the center of the  original Hubble Ultra Deep Field. The XDF is a small fraction of the angular diameter of the  full Moon.
The Hubble Ultra Deep Field is an image of a small area of space in the constellation  Fornax, created using Hubble Space Telescope data from 2003 and 2004. By collecting  faint light over many hours of observation, it revealed thousands of galaxies, both nearby  and very distant, making it the deepest image of the universe ever taken at that time.  
The new full-color XDF image reaches much fainter galaxies, and includes very deep  exposures in red light from Hubble's new infrared camera, enabling new studies of the  earliest galaxies in the universe. The XDF contains about 5,500 galaxies even within its  smaller field of view. The faintest galaxies are one ten-billionth the brightness of what  the human eye can see.
Magnificent spiral galaxies similar in shape to our Milky Way and the neighboring  Andromeda galaxy appear in this image, as do the large, fuzzy red galaxies where the  formation of new stars has ceased. These red galaxies are the remnants of dramatic  collisions between galaxies and are in their declining years. Peppered across the field are  tiny, faint, more distant galaxies that were like the seedlings from which today's striking  galaxies grew. The history of galaxies — from soon after the first galaxies were born to the  great galaxies of today, like our Milky Way — is laid out in this one remarkable image.
Hubble pointed at a tiny patch of southern sky in repeat visits (made over the past decade)  for a total of 50 days, with a total exposure time of 2 million seconds. More than 2,000  images of the same field were taken with Hubble's two premier cameras — the Advanced  Camera for Surveys and the Wide Field Camera 3, which extends Hubble's vision into  near-infrared light — and combined to make the XDF.
"The XDF is the deepest image of the sky ever obtained and reveals the faintest and most  distant galaxies ever seen. XDF allows us to explore further back in time than ever before," said Garth Illingworth of the University of California at Santa Cruz, principal investigator of  the Hubble Ultra Deep Field 2009 (HUDF09) program.
The universe is 13.7 billion years old, and the XDF reveals galaxies that span back 13.2  billion years in time. Most of the galaxies in the XDF are seen when they were young, small,  and growing, often violently as they collided and merged together. The early universe was  a time of dramatic birth for galaxies containing brilliant blue stars extraordinarily brighter  than our Sun. The light from those past events is just arriving at Earth now, and so the XDF  is a "time tunnel into the distant past." The youngest galaxy found in the XDF existed just  450 million years after the universe's birth in the big bang.
Before Hubble was launched in 1990, astronomers could barely see normal galaxies to 7  billion light-years away, about halfway across the universe. Observations with telescopes  on the ground were not able to establish how galaxies formed and evolved in the early  universe.
Hubble gave astronomers their first view of the actual forms and shapes of galaxies when  they were young. This provided compelling, direct visual evidence that the universe is truly  changing as it ages. Like watching individual frames of a motion picture, the Hubble deep  surveys reveal the emergence of structure in the infant universe and the subsequent  dynamic stages of galaxy evolution.
The infrared vision of NASA's planned James Webb Space Telescope (Webb telescope)  will be aimed at the XDF. The Webb telescope will find even fainter galaxies that existed  when the universe was just a few hundred million years old. Because of the expansion of  the universe, light from the distant past is stretched into longer, infrared wavelengths. The  Webb telescope's infrared vision is ideally suited to push the XDF even deeper, into a time  when the first stars and galaxies formed and filled the early "dark ages" of the universe with  light.
The XDF/HUDF09 team members are G. Illingworth (University of California, Santa Cruz), R. Bouwens  (Leiden University), M. Carollo (Swiss Federal Institute of Technology, Zurich (ETH)), M. Franx  (Leiden University), V. Gonzalez (University of California, Santa Cruz), I. Labbe (Leiden  University), D. Magee and P. Oesch (University of California, Santa Cruz), M. Stiavelli (Space  Telescope Science Institute), M. Trenti (University of Cambridge), and P. van Dokkum (Yale  University).
The public is invited to participate in a "Meet the Hubble eXtreme Deep Field Observing Team" webinar,  in which three key astronomers of the XDF observing team will describe how they assembled the  landmark image and explain what it tells us about the evolving universe. Participants are invited  to send in questions for the panel of experts to discuss. The webinar will be broadcast at  1:00 p.m. EDT on Thursday, September 27, 2012. To participate in the webinar, please visit:  http://hubblesite.org/go/xdf/ .
For additional information, contact:
Ray Villard
Space Telescope Science Institute, Baltimore, Md.
410-338-4514
villard@stsci.edu
Garth Illingworth
University of California, Santa Cruz, Calif.
831-459-2843
gdi@ucolick.org
Object Names: Hubble eXtreme Deep Field, XDF
Image Type: Astronomical

Credit: NASA, ESA, G. Illingworth, D. Magee, and P. Oesch (University of California, Santa  Cruz), R. Bouwens (Leiden University), and the HUDF09 Team

源地址：http://asweb.asiaa.sinica.edu.tw/modules/news/article.php?storyid=510
一如摄影者总会将其最佳作品集结成photo portfolio，天文学家也为人类迄今对宇宙最深远的凝视和认识做出最新诠释，但是，只透过一张图；NASA新公布的哈柏极深空影像—”XDF”。

这张图，汇集哈柏太空望远镜10年功力于一，被取名为”eXtreme Deep Field: XDF”(简称UDF)，它是「哈柏深空图像」(HubbleUltra Deep Field，以下简称UDF)的新一代进阶版，仅取景自UDF中央的一小块天区，这块区域，范围相当的小，视直径仅只有满月的几十分之一。

UDF特写的是天炉座中一小块天区，那是以哈柏望远镜2003年到2004年所取得的图像为数据组合而成的一张图。UDF使用不少观测时间，取得了成千星系既微弱又珍贵的光线，以图像为世人呈现了我们的宇宙里，不分远近、老少皆有、仪态万千的各种星系。10年前，UDF是当代全宇宙最深景像的最佳代表作。

NASA最新公布的全彩XDF图像，影像比上一代UDF更锐利，虽然视野更小，其中却塞满多达5,500个星系，最黯淡星系的亮度甚至只有人类视力可分辨亮度的百亿分之一。

在这张图像中，既出现形状外观上与银河系及仙女座星系近似，以其壮丽而很有可看性著称的「螺旋星系」；同时它也内嵌着许许多多已停止形成新恒星、比较大、但形状模模糊糊的那些「红星系」，红星系是星系之间戏剧性碰撞后的残骸，属于星系已步入演化末期的「晚年」。另外还有许多暗淡、遥远、微小的星系，像胡椒粉一样洒满在这整张图像上--今天看来很壮观的星系，在早期的幼儿园阶段，样貌大约就是如此。从宇宙中的第一代星系直到今天像我们银河系这样巨大的星系，它一律兼容并蓄的这么一张锐利图像里，蕴含着如此广博的星系宇宙历史，精采得令人惊叹。

哈柏太空望远镜过去10年中，上千次地重复造访了这块位于南天的天区，并拍摄影像，总曝光时间达200万秒。哈柏望远镜上两个主要相机：先进巡天照相机和哈柏3号广角相机，在这块天区里共拍摄了近2,000张以上的图像。哈柏3号广角相机并且将哈柏太空望远镜的视野推到近红外光波段。

「哈柏超深空2009计划」(HUDF 2009)的计划主持人表示，XDF是目前为止，景深最深的一张天空图像，它为我们揭露了最暗、最遥远星系的样貌，也让我们的探索领域可以朝宇宙更早时期更推前一步。

目前的宇宙是137亿岁，XDF影像中我们可以看到来自132亿年前的星系所发出的光。在XDF这张影像中我们所看见的大多数星系，因为其实都还极为年轻，所以很小，后来它们将会在碰撞和合并事件中经历到猛烈地成长。在宇宙早期，含有明亮的蓝色恒星的星系大量活泼地诞生，那些蓝色恒星，远比我们的太阳还明亮得多。源自远古的过去事件而来的光，经历了漫长旅程，直到现在才抵达地球。XDF，等于像是一座让我们可直通遥远过去的时空隧道。在这张XDF图像里所找得到的最年轻星系，距离宇宙诞生的「大霹雳」，仅仅只有4.5亿年而已。

哈柏太空望远镜是发射升空于1990年。在此之前，只要远于70亿光年以外，一般正常的星系，天文学家几乎是看不到的，那意味着人类看宇宙的能见度仅只及于整个宇宙的一半。当时，单单透过地面型望远镜的观测，想了解早期宇宙中星系如何形成和演化似乎是遥不可及的目标。

因为有了哈柏望远镜开始捎回地球的那些影像，天文学家才第一次看得见星系早期实际形式和形状如何，那也是直接证据能证明：宇宙的确会随着时间进程而改变。像一出每一桢画格都停格一次的动画，哈柏深空调查向我们展现了婴儿时期的宇宙如何出现结构，随后，星系又经过了哪些活力四射的演化。

专精于红外线波段的詹姆斯韦伯太空望远镜(简称JWST)，未来它的观测重点即将会是放在这张XDF图像的视野之中。JWST的任务是，找到存在于宇宙只有几亿岁时那些光线更微弱的星系。因为宇宙膨胀的关系，从遥远的过去而来的光线会被拉长，位移到波长较长的红外光波段区。JWST的「红外视线」能力因此特别适合于将XDF里所暗藏的影像再做进一步更深入的探索，以求得第一代恒星和星系形成时，发出了光、照亮了宇宙黑暗时期的那些珍贵影像。JWST预定于2018年发射。

至于这张哈柏XDF图像的探索之旅，可能最快在今年年底就会有更进阶版的公布，根据BBC报导指出，由美英两国天文学者合组的一个团队已经再多取得了哈柏望远镜100小时以上的时间，进行进一步观测，届时可望能看得到更古老的星系。(Lauren　译）

(图片来源: NASA; ESA; G.Illingworth, D. Magee, and P. Oesch, University of California, Santa Cruz; R.Bouwens, Leiden University; and the HUDF09 Team)

Open in new window这幅图中XDF和月亮的相对位置和实际观测的画面并不相同，在此将它们并列，是为了比较两者的「角大小」。如果你将手臂朝月亮伸直的话，一根手指头比图中这颗月亮还宽两倍。而XDF和满月相比，只有几十分之一而已。(图片版权: NASA; ESA; and Z. Levay, STScI; 月球影像版权: T. Rector; I.Dell'Antonio/NOAO/AURA/NSF)

哈勃把人类的视野扩大了一倍。期待詹姆斯韦伯将带来的震憾。

这全是星系吗。。。

翻译应该包含标题啊，你写英文标题，影响帖子的关注率啊

超深空场啊