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http://hubblesite.org/newscenter/archive/releases/2009/11/
March 12, 2009 09:00 AM (EDT)
News Release Number: STScI-2009-11
太空望远镜科研所2009年第11#新闻公报，美国东部时间2009.03.12 09:00公布。
Hubble Provides New Evidence for Dark Matter Around Small Galaxies
哈勃发现暗物质环绕矮星系的新证据
NASA's Hubble Space Telescope has uncovered a strong new line of evidence that galaxies are embedded in halos of dark matter.
哈勃已经发现了（矮）星系深植在暗物质晕中的一系列新的强力证据。
Peering into the tumultuous heart of the nearby Perseus galaxycluster, Hubble discovered a large population of small galaxies that have remained intact while larger galaxies around them are being ripped apart by the gravitational tug of other galaxies.
在我们的近邻英仙座星系团（嘿嘿，后文会提到是2.5亿光年的邻居），哈勃深入其混乱的核心区域，发现大量矮星系保持了完整的形状，而其周围的大星系已经开始被星系间的引力场互相撕扯变形（短文翻译过了知道意思，文句就更通顺了）。
Dark matter is an invisible form of matter that accounts for most of the universe's mass. Astronomers have deduced the existence of dark matter by observing its gravitational influence on normal matter,consisting of stars, gas, and dust.
暗物质是不可见物质，它们占宇宙物质的大部分比例。天文学家从它们对正常物质（包括恒星、气体、尘埃等）的引力作用推论它们的存在。
The Hubble images provide further evidence that the undisturbed galaxies are enshrouded by a "cushion" of dark matter, which protectsthem from their rough-and-tumble neighborhood.
哈勃拍摄的（高清晰）图片提供了进一步的证据（图在4楼），表明这些稳定的星系被暗物质组成的“缓冲垫”所遮蔽，使它们与周围混乱的环境隔离。
"We were surprised to find so many dwarf galaxies in the core of this cluster that were so smooth and round and had no evidence at all of any kind of disturbance," says astronomer Christopher Conselice of the University of Nottingham, U.K., and leader of the Hubbleobservations. "These dwarfs are very old galaxies that have been in the cluster a long time. So if something was going to disrupt them, it would have happened by now. They must be very, verydark-matter-dominated galaxies."
“我们惊讶的发现英仙座星系团的核心区有这么多矮星系，而且它们是如此光滑圆顺，没有任何受到（引力）扰动的迹象。”Hubble观察项目领导者、英国诺丁汉大学天文学家Christopher Conselice（这位是暗物质研究方面超级大牛级人物，貌似比我国的那些所谓大牛强多了）说。“这些矮星系是非常老的星系，在星系团中已经很长时间了。所以如果有什么（引力扰动）要瓦解它们的话，这事情早就发生了。它们必须是被暗物质完全、彻底控制的星系”。
The dwarf galaxies may have an even higher amount of dark matter than spiral galaxies. "With these results, we cannot say whether the dark-matter content of the dwarfs is higher than in the Milky WayGalaxy," Conselice says. "Although, the fact that spiral galaxies are destroyed in clusters, while the dwarfs are not, suggests that is indeed the case."
矮星系可能包含比涡旋星系更多的暗物质，“虽然我们还不能说（这些）矮星系的暗物质比银河系中的更多”，Christopher Conselice说。“无论如何，事实是星系团中的涡旋星系已经被消灭，而暗星系还在，所以推论是这个原因吧”。（我是意译，原文的根据这些结果什么的太拗口了，去掉）
First proposed about 80 years ago, dark matter is thought to be the "glue" that holds galaxies together. Astronomers suggest that darkmatter provides a vital "scaffolding" for the universe, forming a framework for the formation of galaxies through gravitational attraction. Previous studies with Hubble and NASA's Chandra X-ray Observatory found evidence of dark matter in entire clusters of galaxies such as the Bullet Cluster. The new Hubble observations continue the search for dark matter in individual galaxies.
在80年前，暗物质被当做星系间的“胶水”而首次提出来。天文学家推测，暗物质是维系宇宙（现状）的一个极为重要的“支架”，各星系通过万有引力形成的构造由暗物质的架构维系（这话太拗口，通俗点说就是如果星系只有我们看见的物质，它们根本不能维持现在的样子，恒星们早就飞散开去了）。在此前的研究中，哈勃和钱德拉X望远镜已经合作发现了完全由暗物质组成的星系（比如子弹星系团）。哈勃的新搜索是在单独的星系中寻找暗物质。
Observations by Hubble's Advanced Camera for Surveys spotted 29 dwarf elliptical galaxies in the Perseus Cluster, located 250 millionlight-years away and one of the closest galaxy clusters to Earth. Of those galaxies, 17 are new discoveries.
哈勃高级巡天望远镜在英仙座星系团内发现了29个矮椭圆星系，其中17个是新发现的。英仙座星系团离我们2.5亿光年，是离地球最近的星系团之一。
Because dark matter cannot be seen, astronomers detected its presence through indirect evidence. The most common method is by measuring the velocities of individual stars or groups of stars as they move randomly in the galaxy or as they rotate around the galaxy. The Perseus Cluster is too far away for telescopes to resolve individual stars and measure their motions. So Conselice and his team derived a new technique for uncovering dark matter in these dwarf galaxies by determining the minimum mass the dwarfs must have to protect them frombeing disrupted by the strong, tidal pull of gravity from larger galaxies.
由于暗物质是看不见的，天文学家是通过它们的（引力）效应间接证实它们。最常用的方法是随机测量星团（球状星团或疏散星团）中单个恒星的速度或者它们围绕星系旋转的速度。英仙座星系团太远了，望远镜不能在星系中分解出单独的恒星来测量它们的速度，所以Conselice被和他的团队设计了一个新的方法来结束这些矮星系的暗物质。他们的方法是：在星系团中，为了保证矮星系本身不被周围的大星系的引力分裂，这个矮星系必须具有的最小质量。（大家可以参考我们太阳系内的例子，彗星经过木星附近就会被木星引力分裂为几个彗星碎片，因为彗星本身质量太小；而它的卫星由于质量较大，就不会被分裂为碎片——译者注）。
Studying these small galaxies in detail was possible only because of the sharpness of Hubble's Advanced Camera for Surveys. Conselice and his team first spied the galaxies with the WIYN Telescope at Kitt Peak National Observatory outside Tucson, Ariz. Those observations,Conselice says, only hinted that many of the galaxies were smooth and therefore dark-matter dominated. "Those ground-based observations couldnot resolve the galaxies, so we needed Hubble imaging to nail it," he says.
能够详细研究这些矮星系的唯一原因是哈勃ACS高级巡天望远镜的高分辨率（2006年坏掉了，现在还没修复）。在美国亚利桑那州南部图森市郊外的基特峰国家天文台，Conselice和他的团队使用3.5米口径的WIYN望远镜首次发现了这些星系。Conselice说，这些观察只能暗示这些星系是如此光滑因此表明它们受到暗物质的控制。“地面望远镜不能（仔细）分辨这些星系，我们需要哈勃的成像系统盯住它”。
The Hubble results appeared in the March 1 issue of the Monthly Notices of the Royal Astronomical Society.
上述哈勃发现发表在3.1的英国皇家天文学会月刊通告上。
Other team members are Samantha J. Penny of the University of Nottingham; Sven De Rijcke of the University of Ghent in Belgium; and Enrico Held of the University of Padua in Italy.
团队其他成员：英国诺丁汉大学的Samantha J. Penny ，比利时根特大学的Sven De Rijcke，意大利帕多瓦大学的Enrico Held等等。
CONTACT Donna Weaver / Ray Villard
Space Telescope Science Institute, Baltimore, Md.
410-338-4493 / 410-338-4514
dweaver@stsci.edu / villard@stsci.edu
Christopher Conselice
University of Nottingham, Nottingham, UK
011-44-115-951-5137
011-44-750-347-6126 (cell)
conselice@nottingham.ac.uk |
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